Merge branches 'barrier.2012.05.09a', 'fixes.2012.04.26a', 'inline.2012.05.02b' and 'srcu.2012.05.07b' into HEAD
barrier: Reduce the amount of disturbance by rcu_barrier() to the rest of
the system. This branch also includes improvements to
RCU_FAST_NO_HZ, which are included here due to conflicts.
fixes: Miscellaneous fixes.
inline: Remaining changes from an abortive attempt to inline
preemptible RCU's __rcu_read_lock(). These are (1) making
exit_rcu() avoid unnecessary work and (2) avoiding having
preemptible RCU record a blocked thread when the scheduler
declines to do a context switch.
srcu: Lai Jiangshan's algorithmic implementation of SRCU, including
call_srcu().
This commit is contained in:
Paul E. McKenney
commit
dc36be4419
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|
@ -47,6 +47,16 @@ irqreader Says to invoke RCU readers from irq level. This is currently
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permit this. (Or, more accurately, variants of RCU that do
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-not- permit this know to ignore this variable.)
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n_barrier_cbs If this is nonzero, RCU barrier testing will be conducted,
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in which case n_barrier_cbs specifies the number of
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RCU callbacks (and corresponding kthreads) to use for
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this testing. The value cannot be negative. If you
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specify this to be non-zero when torture_type indicates a
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synchronous RCU implementation (one for which a member of
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the synchronize_rcu() rather than the call_rcu() family is
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used -- see the documentation for torture_type below), an
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error will be reported and no testing will be carried out.
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nfakewriters This is the number of RCU fake writer threads to run. Fake
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writer threads repeatedly use the synchronous "wait for
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current readers" function of the interface selected by
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@ -188,7 +198,7 @@ OUTPUT
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The statistics output is as follows:
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rcu-torture:--- Start of test: nreaders=16 nfakewriters=4 stat_interval=30 verbose=0 test_no_idle_hz=1 shuffle_interval=3 stutter=5 irqreader=1 fqs_duration=0 fqs_holdoff=0 fqs_stutter=3 test_boost=1/0 test_boost_interval=7 test_boost_duration=4
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rcu-torture: rtc: (null) ver: 155441 tfle: 0 rta: 155441 rtaf: 8884 rtf: 155440 rtmbe: 0 rtbke: 0 rtbre: 0 rtbf: 0 rtb: 0 nt: 3055767
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rcu-torture: rtc: (null) ver: 155441 tfle: 0 rta: 155441 rtaf: 8884 rtf: 155440 rtmbe: 0 rtbe: 0 rtbke: 0 rtbre: 0 rtbf: 0 rtb: 0 nt: 3055767
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rcu-torture: Reader Pipe: 727860534 34213 0 0 0 0 0 0 0 0 0
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rcu-torture: Reader Batch: 727877838 17003 0 0 0 0 0 0 0 0 0
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rcu-torture: Free-Block Circulation: 155440 155440 155440 155440 155440 155440 155440 155440 155440 155440 0
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@ -230,6 +240,9 @@ o "rtmbe": A non-zero value indicates that rcutorture believes that
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rcu_assign_pointer() and rcu_dereference() are not working
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correctly. This value should be zero.
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o "rtbe": A non-zero value indicates that one of the rcu_barrier()
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family of functions is not working correctly.
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o "rtbke": rcutorture was unable to create the real-time kthreads
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used to force RCU priority inversion. This value should be zero.
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|
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@ -2330,18 +2330,100 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
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ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
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See Documentation/blockdev/ramdisk.txt.
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rcupdate.blimit= [KNL,BOOT]
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rcutree.blimit= [KNL,BOOT]
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Set maximum number of finished RCU callbacks to process
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in one batch.
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rcupdate.qhimark= [KNL,BOOT]
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rcutree.qhimark= [KNL,BOOT]
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Set threshold of queued
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RCU callbacks over which batch limiting is disabled.
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rcupdate.qlowmark= [KNL,BOOT]
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rcutree.qlowmark= [KNL,BOOT]
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Set threshold of queued RCU callbacks below which
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batch limiting is re-enabled.
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rcutree.rcu_cpu_stall_suppress= [KNL,BOOT]
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Suppress RCU CPU stall warning messages.
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rcutree.rcu_cpu_stall_timeout= [KNL,BOOT]
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Set timeout for RCU CPU stall warning messages.
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rcutorture.fqs_duration= [KNL,BOOT]
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Set duration of force_quiescent_state bursts.
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rcutorture.fqs_holdoff= [KNL,BOOT]
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Set holdoff time within force_quiescent_state bursts.
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rcutorture.fqs_stutter= [KNL,BOOT]
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Set wait time between force_quiescent_state bursts.
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rcutorture.irqreader= [KNL,BOOT]
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Test RCU readers from irq handlers.
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rcutorture.n_barrier_cbs= [KNL,BOOT]
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Set callbacks/threads for rcu_barrier() testing.
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rcutorture.nfakewriters= [KNL,BOOT]
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Set number of concurrent RCU writers. These just
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stress RCU, they don't participate in the actual
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test, hence the "fake".
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rcutorture.nreaders= [KNL,BOOT]
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Set number of RCU readers.
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rcutorture.onoff_holdoff= [KNL,BOOT]
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Set time (s) after boot for CPU-hotplug testing.
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rcutorture.onoff_interval= [KNL,BOOT]
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Set time (s) between CPU-hotplug operations, or
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zero to disable CPU-hotplug testing.
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rcutorture.shuffle_interval= [KNL,BOOT]
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Set task-shuffle interval (s). Shuffling tasks
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allows some CPUs to go into dyntick-idle mode
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during the rcutorture test.
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rcutorture.shutdown_secs= [KNL,BOOT]
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Set time (s) after boot system shutdown. This
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is useful for hands-off automated testing.
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rcutorture.stall_cpu= [KNL,BOOT]
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Duration of CPU stall (s) to test RCU CPU stall
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warnings, zero to disable.
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rcutorture.stall_cpu_holdoff= [KNL,BOOT]
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Time to wait (s) after boot before inducing stall.
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rcutorture.stat_interval= [KNL,BOOT]
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Time (s) between statistics printk()s.
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rcutorture.stutter= [KNL,BOOT]
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Time (s) to stutter testing, for example, specifying
|
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five seconds causes the test to run for five seconds,
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wait for five seconds, and so on. This tests RCU's
|
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ability to transition abruptly to and from idle.
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rcutorture.test_boost= [KNL,BOOT]
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Test RCU priority boosting? 0=no, 1=maybe, 2=yes.
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"Maybe" means test if the RCU implementation
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under test support RCU priority boosting.
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rcutorture.test_boost_duration= [KNL,BOOT]
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Duration (s) of each individual boost test.
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rcutorture.test_boost_interval= [KNL,BOOT]
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Interval (s) between each boost test.
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rcutorture.test_no_idle_hz= [KNL,BOOT]
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Test RCU's dyntick-idle handling. See also the
|
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rcutorture.shuffle_interval parameter.
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rcutorture.torture_type= [KNL,BOOT]
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Specify the RCU implementation to test.
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rcutorture.verbose= [KNL,BOOT]
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Enable additional printk() statements.
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|
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rdinit= [KNL]
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Format: <full_path>
|
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Run specified binary instead of /init from the ramdisk,
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|
|
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14
MAINTAINERS
14
MAINTAINERS
|
|
@ -5607,14 +5607,13 @@ F: net/rds/
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|||
READ-COPY UPDATE (RCU)
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M: Dipankar Sarma <dipankar@in.ibm.com>
|
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M: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
|
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W: http://www.rdrop.com/users/paulmck/rclock/
|
||||
W: http://www.rdrop.com/users/paulmck/RCU/
|
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S: Supported
|
||||
T: git git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu.git
|
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F: Documentation/RCU/
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X: Documentation/RCU/torture.txt
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F: include/linux/rcu*
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F: include/linux/srcu*
|
||||
F: kernel/rcu*
|
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F: kernel/srcu*
|
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X: kernel/rcutorture.c
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|
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REAL TIME CLOCK (RTC) SUBSYSTEM
|
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|
|
@ -6131,6 +6130,15 @@ S: Maintained
|
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F: include/linux/sl?b*.h
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F: mm/sl?b.c
|
||||
|
||||
SLEEPABLE READ-COPY UPDATE (SRCU)
|
||||
M: Lai Jiangshan <laijs@cn.fujitsu.com>
|
||||
M: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
|
||||
W: http://www.rdrop.com/users/paulmck/RCU/
|
||||
S: Supported
|
||||
T: git git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu.git
|
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F: include/linux/srcu*
|
||||
F: kernel/srcu*
|
||||
|
||||
SMC91x ETHERNET DRIVER
|
||||
M: Nicolas Pitre <nico@fluxnic.net>
|
||||
S: Odd Fixes
|
||||
|
|
|
|||
|
|
@ -705,6 +705,7 @@ static void stack_proc(void *arg)
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struct task_struct *from = current, *to = arg;
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|
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to->thread.saved_task = from;
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rcu_switch_from(from);
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switch_to(from, to, from);
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}
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|
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|
|
|
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|
|
@ -30,6 +30,7 @@
|
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* This is only for internal list manipulation where we know
|
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* the prev/next entries already!
|
||||
*/
|
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#ifndef CONFIG_DEBUG_LIST
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static inline void __list_add_rcu(struct list_head *new,
|
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struct list_head *prev, struct list_head *next)
|
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{
|
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|
|
@ -38,6 +39,10 @@ static inline void __list_add_rcu(struct list_head *new,
|
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rcu_assign_pointer(list_next_rcu(prev), new);
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next->prev = new;
|
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}
|
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#else
|
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extern void __list_add_rcu(struct list_head *new,
|
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struct list_head *prev, struct list_head *next);
|
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#endif
|
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|
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/**
|
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* list_add_rcu - add a new entry to rcu-protected list
|
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|
|
@ -108,7 +113,7 @@ static inline void list_add_tail_rcu(struct list_head *new,
|
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*/
|
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static inline void list_del_rcu(struct list_head *entry)
|
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{
|
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__list_del(entry->prev, entry->next);
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__list_del_entry(entry);
|
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entry->prev = LIST_POISON2;
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}
|
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|
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|
|
@ -228,18 +233,43 @@ static inline void list_splice_init_rcu(struct list_head *list,
|
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})
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|
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/**
|
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* list_first_entry_rcu - get the first element from a list
|
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* Where are list_empty_rcu() and list_first_entry_rcu()?
|
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*
|
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* Implementing those functions following their counterparts list_empty() and
|
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* list_first_entry() is not advisable because they lead to subtle race
|
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* conditions as the following snippet shows:
|
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*
|
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* if (!list_empty_rcu(mylist)) {
|
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* struct foo *bar = list_first_entry_rcu(mylist, struct foo, list_member);
|
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* do_something(bar);
|
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* }
|
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*
|
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* The list may not be empty when list_empty_rcu checks it, but it may be when
|
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* list_first_entry_rcu rereads the ->next pointer.
|
||||
*
|
||||
* Rereading the ->next pointer is not a problem for list_empty() and
|
||||
* list_first_entry() because they would be protected by a lock that blocks
|
||||
* writers.
|
||||
*
|
||||
* See list_first_or_null_rcu for an alternative.
|
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*/
|
||||
|
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/**
|
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* list_first_or_null_rcu - get the first element from a list
|
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* @ptr: the list head to take the element from.
|
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* @type: the type of the struct this is embedded in.
|
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* @member: the name of the list_struct within the struct.
|
||||
*
|
||||
* Note, that list is expected to be not empty.
|
||||
* Note that if the list is empty, it returns NULL.
|
||||
*
|
||||
* This primitive may safely run concurrently with the _rcu list-mutation
|
||||
* primitives such as list_add_rcu() as long as it's guarded by rcu_read_lock().
|
||||
*/
|
||||
#define list_first_entry_rcu(ptr, type, member) \
|
||||
list_entry_rcu((ptr)->next, type, member)
|
||||
#define list_first_or_null_rcu(ptr, type, member) \
|
||||
({struct list_head *__ptr = (ptr); \
|
||||
struct list_head __rcu *__next = list_next_rcu(__ptr); \
|
||||
likely(__ptr != __next) ? container_of(__next, type, member) : NULL; \
|
||||
})
|
||||
|
||||
/**
|
||||
* list_for_each_entry_rcu - iterate over rcu list of given type
|
||||
|
|
|
|||
|
|
@ -184,12 +184,14 @@ static inline int rcu_preempt_depth(void)
|
|||
/* Internal to kernel */
|
||||
extern void rcu_sched_qs(int cpu);
|
||||
extern void rcu_bh_qs(int cpu);
|
||||
extern void rcu_preempt_note_context_switch(void);
|
||||
extern void rcu_check_callbacks(int cpu, int user);
|
||||
struct notifier_block;
|
||||
extern void rcu_idle_enter(void);
|
||||
extern void rcu_idle_exit(void);
|
||||
extern void rcu_irq_enter(void);
|
||||
extern void rcu_irq_exit(void);
|
||||
extern void exit_rcu(void);
|
||||
|
||||
/**
|
||||
* RCU_NONIDLE - Indicate idle-loop code that needs RCU readers
|
||||
|
|
@ -922,6 +924,21 @@ void __kfree_rcu(struct rcu_head *head, unsigned long offset)
|
|||
kfree_call_rcu(head, (rcu_callback)offset);
|
||||
}
|
||||
|
||||
/*
|
||||
* Does the specified offset indicate that the corresponding rcu_head
|
||||
* structure can be handled by kfree_rcu()?
|
||||
*/
|
||||
#define __is_kfree_rcu_offset(offset) ((offset) < 4096)
|
||||
|
||||
/*
|
||||
* Helper macro for kfree_rcu() to prevent argument-expansion eyestrain.
|
||||
*/
|
||||
#define __kfree_rcu(head, offset) \
|
||||
do { \
|
||||
BUILD_BUG_ON(!__is_kfree_rcu_offset(offset)); \
|
||||
call_rcu(head, (void (*)(struct rcu_head *))(unsigned long)(offset)); \
|
||||
} while (0)
|
||||
|
||||
/**
|
||||
* kfree_rcu() - kfree an object after a grace period.
|
||||
* @ptr: pointer to kfree
|
||||
|
|
@ -944,6 +961,9 @@ void __kfree_rcu(struct rcu_head *head, unsigned long offset)
|
|||
*
|
||||
* Note that the allowable offset might decrease in the future, for example,
|
||||
* to allow something like kmem_cache_free_rcu().
|
||||
*
|
||||
* The BUILD_BUG_ON check must not involve any function calls, hence the
|
||||
* checks are done in macros here.
|
||||
*/
|
||||
#define kfree_rcu(ptr, rcu_head) \
|
||||
__kfree_rcu(&((ptr)->rcu_head), offsetof(typeof(*(ptr)), rcu_head))
|
||||
|
|
|
|||
|
|
@ -87,14 +87,6 @@ static inline void kfree_call_rcu(struct rcu_head *head,
|
|||
|
||||
#ifdef CONFIG_TINY_RCU
|
||||
|
||||
static inline void rcu_preempt_note_context_switch(void)
|
||||
{
|
||||
}
|
||||
|
||||
static inline void exit_rcu(void)
|
||||
{
|
||||
}
|
||||
|
||||
static inline int rcu_needs_cpu(int cpu)
|
||||
{
|
||||
return 0;
|
||||
|
|
@ -102,8 +94,6 @@ static inline int rcu_needs_cpu(int cpu)
|
|||
|
||||
#else /* #ifdef CONFIG_TINY_RCU */
|
||||
|
||||
void rcu_preempt_note_context_switch(void);
|
||||
extern void exit_rcu(void);
|
||||
int rcu_preempt_needs_cpu(void);
|
||||
|
||||
static inline int rcu_needs_cpu(int cpu)
|
||||
|
|
@ -116,7 +106,6 @@ static inline int rcu_needs_cpu(int cpu)
|
|||
static inline void rcu_note_context_switch(int cpu)
|
||||
{
|
||||
rcu_sched_qs(cpu);
|
||||
rcu_preempt_note_context_switch();
|
||||
}
|
||||
|
||||
/*
|
||||
|
|
|
|||
|
|
@ -45,18 +45,6 @@ static inline void rcu_virt_note_context_switch(int cpu)
|
|||
rcu_note_context_switch(cpu);
|
||||
}
|
||||
|
||||
#ifdef CONFIG_TREE_PREEMPT_RCU
|
||||
|
||||
extern void exit_rcu(void);
|
||||
|
||||
#else /* #ifdef CONFIG_TREE_PREEMPT_RCU */
|
||||
|
||||
static inline void exit_rcu(void)
|
||||
{
|
||||
}
|
||||
|
||||
#endif /* #else #ifdef CONFIG_TREE_PREEMPT_RCU */
|
||||
|
||||
extern void synchronize_rcu_bh(void);
|
||||
extern void synchronize_sched_expedited(void);
|
||||
extern void synchronize_rcu_expedited(void);
|
||||
|
|
@ -98,13 +86,6 @@ extern void rcu_force_quiescent_state(void);
|
|||
extern void rcu_bh_force_quiescent_state(void);
|
||||
extern void rcu_sched_force_quiescent_state(void);
|
||||
|
||||
/* A context switch is a grace period for RCU-sched and RCU-bh. */
|
||||
static inline int rcu_blocking_is_gp(void)
|
||||
{
|
||||
might_sleep(); /* Check for RCU read-side critical section. */
|
||||
return num_online_cpus() == 1;
|
||||
}
|
||||
|
||||
extern void rcu_scheduler_starting(void);
|
||||
extern int rcu_scheduler_active __read_mostly;
|
||||
|
||||
|
|
|
|||
|
|
@ -1905,12 +1905,22 @@ static inline void rcu_copy_process(struct task_struct *p)
|
|||
INIT_LIST_HEAD(&p->rcu_node_entry);
|
||||
}
|
||||
|
||||
static inline void rcu_switch_from(struct task_struct *prev)
|
||||
{
|
||||
if (prev->rcu_read_lock_nesting != 0)
|
||||
rcu_preempt_note_context_switch();
|
||||
}
|
||||
|
||||
#else
|
||||
|
||||
static inline void rcu_copy_process(struct task_struct *p)
|
||||
{
|
||||
}
|
||||
|
||||
static inline void rcu_switch_from(struct task_struct *prev)
|
||||
{
|
||||
}
|
||||
|
||||
#endif
|
||||
|
||||
#ifdef CONFIG_SMP
|
||||
|
|
|
|||
|
|
@ -29,26 +29,35 @@
|
|||
|
||||
#include <linux/mutex.h>
|
||||
#include <linux/rcupdate.h>
|
||||
#include <linux/workqueue.h>
|
||||
|
||||
struct srcu_struct_array {
|
||||
int c[2];
|
||||
unsigned long c[2];
|
||||
unsigned long seq[2];
|
||||
};
|
||||
|
||||
struct rcu_batch {
|
||||
struct rcu_head *head, **tail;
|
||||
};
|
||||
|
||||
struct srcu_struct {
|
||||
int completed;
|
||||
unsigned completed;
|
||||
struct srcu_struct_array __percpu *per_cpu_ref;
|
||||
struct mutex mutex;
|
||||
spinlock_t queue_lock; /* protect ->batch_queue, ->running */
|
||||
bool running;
|
||||
/* callbacks just queued */
|
||||
struct rcu_batch batch_queue;
|
||||
/* callbacks try to do the first check_zero */
|
||||
struct rcu_batch batch_check0;
|
||||
/* callbacks done with the first check_zero and the flip */
|
||||
struct rcu_batch batch_check1;
|
||||
struct rcu_batch batch_done;
|
||||
struct delayed_work work;
|
||||
#ifdef CONFIG_DEBUG_LOCK_ALLOC
|
||||
struct lockdep_map dep_map;
|
||||
#endif /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */
|
||||
};
|
||||
|
||||
#ifndef CONFIG_PREEMPT
|
||||
#define srcu_barrier() barrier()
|
||||
#else /* #ifndef CONFIG_PREEMPT */
|
||||
#define srcu_barrier()
|
||||
#endif /* #else #ifndef CONFIG_PREEMPT */
|
||||
|
||||
#ifdef CONFIG_DEBUG_LOCK_ALLOC
|
||||
|
||||
int __init_srcu_struct(struct srcu_struct *sp, const char *name,
|
||||
|
|
@ -67,12 +76,33 @@ int init_srcu_struct(struct srcu_struct *sp);
|
|||
|
||||
#endif /* #else #ifdef CONFIG_DEBUG_LOCK_ALLOC */
|
||||
|
||||
/**
|
||||
* call_srcu() - Queue a callback for invocation after an SRCU grace period
|
||||
* @sp: srcu_struct in queue the callback
|
||||
* @head: structure to be used for queueing the SRCU callback.
|
||||
* @func: function to be invoked after the SRCU grace period
|
||||
*
|
||||
* The callback function will be invoked some time after a full SRCU
|
||||
* grace period elapses, in other words after all pre-existing SRCU
|
||||
* read-side critical sections have completed. However, the callback
|
||||
* function might well execute concurrently with other SRCU read-side
|
||||
* critical sections that started after call_srcu() was invoked. SRCU
|
||||
* read-side critical sections are delimited by srcu_read_lock() and
|
||||
* srcu_read_unlock(), and may be nested.
|
||||
*
|
||||
* The callback will be invoked from process context, but must nevertheless
|
||||
* be fast and must not block.
|
||||
*/
|
||||
void call_srcu(struct srcu_struct *sp, struct rcu_head *head,
|
||||
void (*func)(struct rcu_head *head));
|
||||
|
||||
void cleanup_srcu_struct(struct srcu_struct *sp);
|
||||
int __srcu_read_lock(struct srcu_struct *sp) __acquires(sp);
|
||||
void __srcu_read_unlock(struct srcu_struct *sp, int idx) __releases(sp);
|
||||
void synchronize_srcu(struct srcu_struct *sp);
|
||||
void synchronize_srcu_expedited(struct srcu_struct *sp);
|
||||
long srcu_batches_completed(struct srcu_struct *sp);
|
||||
void srcu_barrier(struct srcu_struct *sp);
|
||||
|
||||
#ifdef CONFIG_DEBUG_LOCK_ALLOC
|
||||
|
||||
|
|
|
|||
50
init/Kconfig
50
init/Kconfig
|
|
@ -458,6 +458,33 @@ config RCU_FANOUT
|
|||
Select a specific number if testing RCU itself.
|
||||
Take the default if unsure.
|
||||
|
||||
config RCU_FANOUT_LEAF
|
||||
int "Tree-based hierarchical RCU leaf-level fanout value"
|
||||
range 2 RCU_FANOUT if 64BIT
|
||||
range 2 RCU_FANOUT if !64BIT
|
||||
depends on TREE_RCU || TREE_PREEMPT_RCU
|
||||
default 16
|
||||
help
|
||||
This option controls the leaf-level fanout of hierarchical
|
||||
implementations of RCU, and allows trading off cache misses
|
||||
against lock contention. Systems that synchronize their
|
||||
scheduling-clock interrupts for energy-efficiency reasons will
|
||||
want the default because the smaller leaf-level fanout keeps
|
||||
lock contention levels acceptably low. Very large systems
|
||||
(hundreds or thousands of CPUs) will instead want to set this
|
||||
value to the maximum value possible in order to reduce the
|
||||
number of cache misses incurred during RCU's grace-period
|
||||
initialization. These systems tend to run CPU-bound, and thus
|
||||
are not helped by synchronized interrupts, and thus tend to
|
||||
skew them, which reduces lock contention enough that large
|
||||
leaf-level fanouts work well.
|
||||
|
||||
Select a specific number if testing RCU itself.
|
||||
|
||||
Select the maximum permissible value for large systems.
|
||||
|
||||
Take the default if unsure.
|
||||
|
||||
config RCU_FANOUT_EXACT
|
||||
bool "Disable tree-based hierarchical RCU auto-balancing"
|
||||
depends on TREE_RCU || TREE_PREEMPT_RCU
|
||||
|
|
@ -515,10 +542,25 @@ config RCU_BOOST_PRIO
|
|||
depends on RCU_BOOST
|
||||
default 1
|
||||
help
|
||||
This option specifies the real-time priority to which preempted
|
||||
RCU readers are to be boosted. If you are working with CPU-bound
|
||||
real-time applications, you should specify a priority higher then
|
||||
the highest-priority CPU-bound application.
|
||||
This option specifies the real-time priority to which long-term
|
||||
preempted RCU readers are to be boosted. If you are working
|
||||
with a real-time application that has one or more CPU-bound
|
||||
threads running at a real-time priority level, you should set
|
||||
RCU_BOOST_PRIO to a priority higher then the highest-priority
|
||||
real-time CPU-bound thread. The default RCU_BOOST_PRIO value
|
||||
of 1 is appropriate in the common case, which is real-time
|
||||
applications that do not have any CPU-bound threads.
|
||||
|
||||
Some real-time applications might not have a single real-time
|
||||
thread that saturates a given CPU, but instead might have
|
||||
multiple real-time threads that, taken together, fully utilize
|
||||
that CPU. In this case, you should set RCU_BOOST_PRIO to
|
||||
a priority higher than the lowest-priority thread that is
|
||||
conspiring to prevent the CPU from running any non-real-time
|
||||
tasks. For example, if one thread at priority 10 and another
|
||||
thread at priority 5 are between themselves fully consuming
|
||||
the CPU time on a given CPU, then RCU_BOOST_PRIO should be
|
||||
set to priority 6 or higher.
|
||||
|
||||
Specify the real-time priority, or take the default if unsure.
|
||||
|
||||
|
|
|
|||
|
|
@ -51,6 +51,34 @@
|
|||
|
||||
#include "rcu.h"
|
||||
|
||||
#ifdef CONFIG_PREEMPT_RCU
|
||||
|
||||
/*
|
||||
* Check for a task exiting while in a preemptible-RCU read-side
|
||||
* critical section, clean up if so. No need to issue warnings,
|
||||
* as debug_check_no_locks_held() already does this if lockdep
|
||||
* is enabled.
|
||||
*/
|
||||
void exit_rcu(void)
|
||||
{
|
||||
struct task_struct *t = current;
|
||||
|
||||
if (likely(list_empty(¤t->rcu_node_entry)))
|
||||
return;
|
||||
t->rcu_read_lock_nesting = 1;
|
||||
barrier();
|
||||
t->rcu_read_unlock_special = RCU_READ_UNLOCK_BLOCKED;
|
||||
__rcu_read_unlock();
|
||||
}
|
||||
|
||||
#else /* #ifdef CONFIG_PREEMPT_RCU */
|
||||
|
||||
void exit_rcu(void)
|
||||
{
|
||||
}
|
||||
|
||||
#endif /* #else #ifdef CONFIG_PREEMPT_RCU */
|
||||
|
||||
#ifdef CONFIG_DEBUG_LOCK_ALLOC
|
||||
static struct lock_class_key rcu_lock_key;
|
||||
struct lockdep_map rcu_lock_map =
|
||||
|
|
|
|||
|
|
@ -851,22 +851,6 @@ int rcu_preempt_needs_cpu(void)
|
|||
return rcu_preempt_ctrlblk.rcb.rcucblist != NULL;
|
||||
}
|
||||
|
||||
/*
|
||||
* Check for a task exiting while in a preemptible -RCU read-side
|
||||
* critical section, clean up if so. No need to issue warnings,
|
||||
* as debug_check_no_locks_held() already does this if lockdep
|
||||
* is enabled.
|
||||
*/
|
||||
void exit_rcu(void)
|
||||
{
|
||||
struct task_struct *t = current;
|
||||
|
||||
if (t->rcu_read_lock_nesting == 0)
|
||||
return;
|
||||
t->rcu_read_lock_nesting = 1;
|
||||
__rcu_read_unlock();
|
||||
}
|
||||
|
||||
#else /* #ifdef CONFIG_TINY_PREEMPT_RCU */
|
||||
|
||||
#ifdef CONFIG_RCU_TRACE
|
||||
|
|
|
|||
|
|
@ -64,6 +64,7 @@ static int irqreader = 1; /* RCU readers from irq (timers). */
|
|||
static int fqs_duration; /* Duration of bursts (us), 0 to disable. */
|
||||
static int fqs_holdoff; /* Hold time within burst (us). */
|
||||
static int fqs_stutter = 3; /* Wait time between bursts (s). */
|
||||
static int n_barrier_cbs; /* Number of callbacks to test RCU barriers. */
|
||||
static int onoff_interval; /* Wait time between CPU hotplugs, 0=disable. */
|
||||
static int onoff_holdoff; /* Seconds after boot before CPU hotplugs. */
|
||||
static int shutdown_secs; /* Shutdown time (s). <=0 for no shutdown. */
|
||||
|
|
@ -96,6 +97,8 @@ module_param(fqs_holdoff, int, 0444);
|
|||
MODULE_PARM_DESC(fqs_holdoff, "Holdoff time within fqs bursts (us)");
|
||||
module_param(fqs_stutter, int, 0444);
|
||||
MODULE_PARM_DESC(fqs_stutter, "Wait time between fqs bursts (s)");
|
||||
module_param(n_barrier_cbs, int, 0444);
|
||||
MODULE_PARM_DESC(n_barrier_cbs, "# of callbacks/kthreads for barrier testing");
|
||||
module_param(onoff_interval, int, 0444);
|
||||
MODULE_PARM_DESC(onoff_interval, "Time between CPU hotplugs (s), 0=disable");
|
||||
module_param(onoff_holdoff, int, 0444);
|
||||
|
|
@ -139,6 +142,8 @@ static struct task_struct *shutdown_task;
|
|||
static struct task_struct *onoff_task;
|
||||
#endif /* #ifdef CONFIG_HOTPLUG_CPU */
|
||||
static struct task_struct *stall_task;
|
||||
static struct task_struct **barrier_cbs_tasks;
|
||||
static struct task_struct *barrier_task;
|
||||
|
||||
#define RCU_TORTURE_PIPE_LEN 10
|
||||
|
||||
|
|
@ -164,6 +169,7 @@ static atomic_t n_rcu_torture_alloc_fail;
|
|||
static atomic_t n_rcu_torture_free;
|
||||
static atomic_t n_rcu_torture_mberror;
|
||||
static atomic_t n_rcu_torture_error;
|
||||
static long n_rcu_torture_barrier_error;
|
||||
static long n_rcu_torture_boost_ktrerror;
|
||||
static long n_rcu_torture_boost_rterror;
|
||||
static long n_rcu_torture_boost_failure;
|
||||
|
|
@ -173,6 +179,8 @@ static long n_offline_attempts;
|
|||
static long n_offline_successes;
|
||||
static long n_online_attempts;
|
||||
static long n_online_successes;
|
||||
static long n_barrier_attempts;
|
||||
static long n_barrier_successes;
|
||||
static struct list_head rcu_torture_removed;
|
||||
static cpumask_var_t shuffle_tmp_mask;
|
||||
|
||||
|
|
@ -197,6 +205,10 @@ static unsigned long shutdown_time; /* jiffies to system shutdown. */
|
|||
static unsigned long boost_starttime; /* jiffies of next boost test start. */
|
||||
DEFINE_MUTEX(boost_mutex); /* protect setting boost_starttime */
|
||||
/* and boost task create/destroy. */
|
||||
static atomic_t barrier_cbs_count; /* Barrier callbacks registered. */
|
||||
static atomic_t barrier_cbs_invoked; /* Barrier callbacks invoked. */
|
||||
static wait_queue_head_t *barrier_cbs_wq; /* Coordinate barrier testing. */
|
||||
static DECLARE_WAIT_QUEUE_HEAD(barrier_wq);
|
||||
|
||||
/* Mediate rmmod and system shutdown. Concurrent rmmod & shutdown illegal! */
|
||||
|
||||
|
|
@ -327,6 +339,7 @@ struct rcu_torture_ops {
|
|||
int (*completed)(void);
|
||||
void (*deferred_free)(struct rcu_torture *p);
|
||||
void (*sync)(void);
|
||||
void (*call)(struct rcu_head *head, void (*func)(struct rcu_head *rcu));
|
||||
void (*cb_barrier)(void);
|
||||
void (*fqs)(void);
|
||||
int (*stats)(char *page);
|
||||
|
|
@ -417,6 +430,7 @@ static struct rcu_torture_ops rcu_ops = {
|
|||
.completed = rcu_torture_completed,
|
||||
.deferred_free = rcu_torture_deferred_free,
|
||||
.sync = synchronize_rcu,
|
||||
.call = call_rcu,
|
||||
.cb_barrier = rcu_barrier,
|
||||
.fqs = rcu_force_quiescent_state,
|
||||
.stats = NULL,
|
||||
|
|
@ -460,6 +474,7 @@ static struct rcu_torture_ops rcu_sync_ops = {
|
|||
.completed = rcu_torture_completed,
|
||||
.deferred_free = rcu_sync_torture_deferred_free,
|
||||
.sync = synchronize_rcu,
|
||||
.call = NULL,
|
||||
.cb_barrier = NULL,
|
||||
.fqs = rcu_force_quiescent_state,
|
||||
.stats = NULL,
|
||||
|
|
@ -477,6 +492,7 @@ static struct rcu_torture_ops rcu_expedited_ops = {
|
|||
.completed = rcu_no_completed,
|
||||
.deferred_free = rcu_sync_torture_deferred_free,
|
||||
.sync = synchronize_rcu_expedited,
|
||||
.call = NULL,
|
||||
.cb_barrier = NULL,
|
||||
.fqs = rcu_force_quiescent_state,
|
||||
.stats = NULL,
|
||||
|
|
@ -519,6 +535,7 @@ static struct rcu_torture_ops rcu_bh_ops = {
|
|||
.completed = rcu_bh_torture_completed,
|
||||
.deferred_free = rcu_bh_torture_deferred_free,
|
||||
.sync = synchronize_rcu_bh,
|
||||
.call = call_rcu_bh,
|
||||
.cb_barrier = rcu_barrier_bh,
|
||||
.fqs = rcu_bh_force_quiescent_state,
|
||||
.stats = NULL,
|
||||
|
|
@ -535,6 +552,7 @@ static struct rcu_torture_ops rcu_bh_sync_ops = {
|
|||
.completed = rcu_bh_torture_completed,
|
||||
.deferred_free = rcu_sync_torture_deferred_free,
|
||||
.sync = synchronize_rcu_bh,
|
||||
.call = NULL,
|
||||
.cb_barrier = NULL,
|
||||
.fqs = rcu_bh_force_quiescent_state,
|
||||
.stats = NULL,
|
||||
|
|
@ -551,6 +569,7 @@ static struct rcu_torture_ops rcu_bh_expedited_ops = {
|
|||
.completed = rcu_bh_torture_completed,
|
||||
.deferred_free = rcu_sync_torture_deferred_free,
|
||||
.sync = synchronize_rcu_bh_expedited,
|
||||
.call = NULL,
|
||||
.cb_barrier = NULL,
|
||||
.fqs = rcu_bh_force_quiescent_state,
|
||||
.stats = NULL,
|
||||
|
|
@ -606,6 +625,11 @@ static int srcu_torture_completed(void)
|
|||
return srcu_batches_completed(&srcu_ctl);
|
||||
}
|
||||
|
||||
static void srcu_torture_deferred_free(struct rcu_torture *rp)
|
||||
{
|
||||
call_srcu(&srcu_ctl, &rp->rtort_rcu, rcu_torture_cb);
|
||||
}
|
||||
|
||||
static void srcu_torture_synchronize(void)
|
||||
{
|
||||
synchronize_srcu(&srcu_ctl);
|
||||
|
|
@ -620,7 +644,7 @@ static int srcu_torture_stats(char *page)
|
|||
cnt += sprintf(&page[cnt], "%s%s per-CPU(idx=%d):",
|
||||
torture_type, TORTURE_FLAG, idx);
|
||||
for_each_possible_cpu(cpu) {
|
||||
cnt += sprintf(&page[cnt], " %d(%d,%d)", cpu,
|
||||
cnt += sprintf(&page[cnt], " %d(%lu,%lu)", cpu,
|
||||
per_cpu_ptr(srcu_ctl.per_cpu_ref, cpu)->c[!idx],
|
||||
per_cpu_ptr(srcu_ctl.per_cpu_ref, cpu)->c[idx]);
|
||||
}
|
||||
|
|
@ -635,13 +659,29 @@ static struct rcu_torture_ops srcu_ops = {
|
|||
.read_delay = srcu_read_delay,
|
||||
.readunlock = srcu_torture_read_unlock,
|
||||
.completed = srcu_torture_completed,
|
||||
.deferred_free = rcu_sync_torture_deferred_free,
|
||||
.deferred_free = srcu_torture_deferred_free,
|
||||
.sync = srcu_torture_synchronize,
|
||||
.call = NULL,
|
||||
.cb_barrier = NULL,
|
||||
.stats = srcu_torture_stats,
|
||||
.name = "srcu"
|
||||
};
|
||||
|
||||
static struct rcu_torture_ops srcu_sync_ops = {
|
||||
.init = srcu_torture_init,
|
||||
.cleanup = srcu_torture_cleanup,
|
||||
.readlock = srcu_torture_read_lock,
|
||||
.read_delay = srcu_read_delay,
|
||||
.readunlock = srcu_torture_read_unlock,
|
||||
.completed = srcu_torture_completed,
|
||||
.deferred_free = rcu_sync_torture_deferred_free,
|
||||
.sync = srcu_torture_synchronize,
|
||||
.call = NULL,
|
||||
.cb_barrier = NULL,
|
||||
.stats = srcu_torture_stats,
|
||||
.name = "srcu_sync"
|
||||
};
|
||||
|
||||
static int srcu_torture_read_lock_raw(void) __acquires(&srcu_ctl)
|
||||
{
|
||||
return srcu_read_lock_raw(&srcu_ctl);
|
||||
|
|
@ -659,13 +699,29 @@ static struct rcu_torture_ops srcu_raw_ops = {
|
|||
.read_delay = srcu_read_delay,
|
||||
.readunlock = srcu_torture_read_unlock_raw,
|
||||
.completed = srcu_torture_completed,
|
||||
.deferred_free = rcu_sync_torture_deferred_free,
|
||||
.deferred_free = srcu_torture_deferred_free,
|
||||
.sync = srcu_torture_synchronize,
|
||||
.call = NULL,
|
||||
.cb_barrier = NULL,
|
||||
.stats = srcu_torture_stats,
|
||||
.name = "srcu_raw"
|
||||
};
|
||||
|
||||
static struct rcu_torture_ops srcu_raw_sync_ops = {
|
||||
.init = srcu_torture_init,
|
||||
.cleanup = srcu_torture_cleanup,
|
||||
.readlock = srcu_torture_read_lock_raw,
|
||||
.read_delay = srcu_read_delay,
|
||||
.readunlock = srcu_torture_read_unlock_raw,
|
||||
.completed = srcu_torture_completed,
|
||||
.deferred_free = rcu_sync_torture_deferred_free,
|
||||
.sync = srcu_torture_synchronize,
|
||||
.call = NULL,
|
||||
.cb_barrier = NULL,
|
||||
.stats = srcu_torture_stats,
|
||||
.name = "srcu_raw_sync"
|
||||
};
|
||||
|
||||
static void srcu_torture_synchronize_expedited(void)
|
||||
{
|
||||
synchronize_srcu_expedited(&srcu_ctl);
|
||||
|
|
@ -680,6 +736,7 @@ static struct rcu_torture_ops srcu_expedited_ops = {
|
|||
.completed = srcu_torture_completed,
|
||||
.deferred_free = rcu_sync_torture_deferred_free,
|
||||
.sync = srcu_torture_synchronize_expedited,
|
||||
.call = NULL,
|
||||
.cb_barrier = NULL,
|
||||
.stats = srcu_torture_stats,
|
||||
.name = "srcu_expedited"
|
||||
|
|
@ -1129,7 +1186,8 @@ rcu_torture_printk(char *page)
|
|||
"rtc: %p ver: %lu tfle: %d rta: %d rtaf: %d rtf: %d "
|
||||
"rtmbe: %d rtbke: %ld rtbre: %ld "
|
||||
"rtbf: %ld rtb: %ld nt: %ld "
|
||||
"onoff: %ld/%ld:%ld/%ld",
|
||||
"onoff: %ld/%ld:%ld/%ld "
|
||||
"barrier: %ld/%ld:%ld",
|
||||
rcu_torture_current,
|
||||
rcu_torture_current_version,
|
||||
list_empty(&rcu_torture_freelist),
|
||||
|
|
@ -1145,14 +1203,17 @@ rcu_torture_printk(char *page)
|
|||
n_online_successes,
|
||||
n_online_attempts,
|
||||
n_offline_successes,
|
||||
n_offline_attempts);
|
||||
n_offline_attempts,
|
||||
n_barrier_successes,
|
||||
n_barrier_attempts,
|
||||
n_rcu_torture_barrier_error);
|
||||
cnt += sprintf(&page[cnt], "\n%s%s ", torture_type, TORTURE_FLAG);
|
||||
if (atomic_read(&n_rcu_torture_mberror) != 0 ||
|
||||
n_rcu_torture_barrier_error != 0 ||
|
||||
n_rcu_torture_boost_ktrerror != 0 ||
|
||||
n_rcu_torture_boost_rterror != 0 ||
|
||||
n_rcu_torture_boost_failure != 0)
|
||||
cnt += sprintf(&page[cnt], " !!!");
|
||||
cnt += sprintf(&page[cnt], "\n%s%s ", torture_type, TORTURE_FLAG);
|
||||
if (i > 1) {
|
||||
n_rcu_torture_boost_failure != 0 ||
|
||||
i > 1) {
|
||||
cnt += sprintf(&page[cnt], "!!! ");
|
||||
atomic_inc(&n_rcu_torture_error);
|
||||
WARN_ON_ONCE(1);
|
||||
|
|
@ -1337,6 +1398,7 @@ static void rcutorture_booster_cleanup(int cpu)
|
|||
|
||||
/* This must be outside of the mutex, otherwise deadlock! */
|
||||
kthread_stop(t);
|
||||
boost_tasks[cpu] = NULL;
|
||||
}
|
||||
|
||||
static int rcutorture_booster_init(int cpu)
|
||||
|
|
@ -1484,13 +1546,15 @@ static void rcu_torture_onoff_cleanup(void)
|
|||
return;
|
||||
VERBOSE_PRINTK_STRING("Stopping rcu_torture_onoff task");
|
||||
kthread_stop(onoff_task);
|
||||
onoff_task = NULL;
|
||||
}
|
||||
|
||||
#else /* #ifdef CONFIG_HOTPLUG_CPU */
|
||||
|
||||
static void
|
||||
static int
|
||||
rcu_torture_onoff_init(void)
|
||||
{
|
||||
return 0;
|
||||
}
|
||||
|
||||
static void rcu_torture_onoff_cleanup(void)
|
||||
|
|
@ -1554,6 +1618,152 @@ static void rcu_torture_stall_cleanup(void)
|
|||
return;
|
||||
VERBOSE_PRINTK_STRING("Stopping rcu_torture_stall_task.");
|
||||
kthread_stop(stall_task);
|
||||
stall_task = NULL;
|
||||
}
|
||||
|
||||
/* Callback function for RCU barrier testing. */
|
||||
void rcu_torture_barrier_cbf(struct rcu_head *rcu)
|
||||
{
|
||||
atomic_inc(&barrier_cbs_invoked);
|
||||
}
|
||||
|
||||
/* kthread function to register callbacks used to test RCU barriers. */
|
||||
static int rcu_torture_barrier_cbs(void *arg)
|
||||
{
|
||||
long myid = (long)arg;
|
||||
struct rcu_head rcu;
|
||||
|
||||
init_rcu_head_on_stack(&rcu);
|
||||
VERBOSE_PRINTK_STRING("rcu_torture_barrier_cbs task started");
|
||||
set_user_nice(current, 19);
|
||||
do {
|
||||
wait_event(barrier_cbs_wq[myid],
|
||||
atomic_read(&barrier_cbs_count) == n_barrier_cbs ||
|
||||
kthread_should_stop() ||
|
||||
fullstop != FULLSTOP_DONTSTOP);
|
||||
if (kthread_should_stop() || fullstop != FULLSTOP_DONTSTOP)
|
||||
break;
|
||||
cur_ops->call(&rcu, rcu_torture_barrier_cbf);
|
||||
if (atomic_dec_and_test(&barrier_cbs_count))
|
||||
wake_up(&barrier_wq);
|
||||
} while (!kthread_should_stop() && fullstop == FULLSTOP_DONTSTOP);
|
||||
VERBOSE_PRINTK_STRING("rcu_torture_barrier_cbs task stopping");
|
||||
rcutorture_shutdown_absorb("rcu_torture_barrier_cbs");
|
||||
while (!kthread_should_stop())
|
||||
schedule_timeout_interruptible(1);
|
||||
cur_ops->cb_barrier();
|
||||
destroy_rcu_head_on_stack(&rcu);
|
||||
return 0;
|
||||
}
|
||||
|
||||
/* kthread function to drive and coordinate RCU barrier testing. */
|
||||
static int rcu_torture_barrier(void *arg)
|
||||
{
|
||||
int i;
|
||||
|
||||
VERBOSE_PRINTK_STRING("rcu_torture_barrier task starting");
|
||||
do {
|
||||
atomic_set(&barrier_cbs_invoked, 0);
|
||||
atomic_set(&barrier_cbs_count, n_barrier_cbs);
|
||||
/* wake_up() path contains the required barriers. */
|
||||
for (i = 0; i < n_barrier_cbs; i++)
|
||||
wake_up(&barrier_cbs_wq[i]);
|
||||
wait_event(barrier_wq,
|
||||
atomic_read(&barrier_cbs_count) == 0 ||
|
||||
kthread_should_stop() ||
|
||||
fullstop != FULLSTOP_DONTSTOP);
|
||||
if (kthread_should_stop() || fullstop != FULLSTOP_DONTSTOP)
|
||||
break;
|
||||
n_barrier_attempts++;
|
||||
cur_ops->cb_barrier();
|
||||
if (atomic_read(&barrier_cbs_invoked) != n_barrier_cbs) {
|
||||
n_rcu_torture_barrier_error++;
|
||||
WARN_ON_ONCE(1);
|
||||
}
|
||||
n_barrier_successes++;
|
||||
schedule_timeout_interruptible(HZ / 10);
|
||||
} while (!kthread_should_stop() && fullstop == FULLSTOP_DONTSTOP);
|
||||
VERBOSE_PRINTK_STRING("rcu_torture_barrier task stopping");
|
||||
rcutorture_shutdown_absorb("rcu_torture_barrier_cbs");
|
||||
while (!kthread_should_stop())
|
||||
schedule_timeout_interruptible(1);
|
||||
return 0;
|
||||
}
|
||||
|
||||
/* Initialize RCU barrier testing. */
|
||||
static int rcu_torture_barrier_init(void)
|
||||
{
|
||||
int i;
|
||||
int ret;
|
||||
|
||||
if (n_barrier_cbs == 0)
|
||||
return 0;
|
||||
if (cur_ops->call == NULL || cur_ops->cb_barrier == NULL) {
|
||||
printk(KERN_ALERT "%s" TORTURE_FLAG
|
||||
" Call or barrier ops missing for %s,\n",
|
||||
torture_type, cur_ops->name);
|
||||
printk(KERN_ALERT "%s" TORTURE_FLAG
|
||||
" RCU barrier testing omitted from run.\n",
|
||||
torture_type);
|
||||
return 0;
|
||||
}
|
||||
atomic_set(&barrier_cbs_count, 0);
|
||||
atomic_set(&barrier_cbs_invoked, 0);
|
||||
barrier_cbs_tasks =
|
||||
kzalloc(n_barrier_cbs * sizeof(barrier_cbs_tasks[0]),
|
||||
GFP_KERNEL);
|
||||
barrier_cbs_wq =
|
||||
kzalloc(n_barrier_cbs * sizeof(barrier_cbs_wq[0]),
|
||||
GFP_KERNEL);
|
||||
if (barrier_cbs_tasks == NULL || barrier_cbs_wq == 0)
|
||||
return -ENOMEM;
|
||||
for (i = 0; i < n_barrier_cbs; i++) {
|
||||
init_waitqueue_head(&barrier_cbs_wq[i]);
|
||||
barrier_cbs_tasks[i] = kthread_run(rcu_torture_barrier_cbs,
|
||||
(void *)(long)i,
|
||||
"rcu_torture_barrier_cbs");
|
||||
if (IS_ERR(barrier_cbs_tasks[i])) {
|
||||
ret = PTR_ERR(barrier_cbs_tasks[i]);
|
||||
VERBOSE_PRINTK_ERRSTRING("Failed to create rcu_torture_barrier_cbs");
|
||||
barrier_cbs_tasks[i] = NULL;
|
||||
return ret;
|
||||
}
|
||||
}
|
||||
barrier_task = kthread_run(rcu_torture_barrier, NULL,
|
||||
"rcu_torture_barrier");
|
||||
if (IS_ERR(barrier_task)) {
|
||||
ret = PTR_ERR(barrier_task);
|
||||
VERBOSE_PRINTK_ERRSTRING("Failed to create rcu_torture_barrier");
|
||||
barrier_task = NULL;
|
||||
}
|
||||
return 0;
|
||||
}
|
||||
|
||||
/* Clean up after RCU barrier testing. */
|
||||
static void rcu_torture_barrier_cleanup(void)
|
||||
{
|
||||
int i;
|
||||
|
||||
if (barrier_task != NULL) {
|
||||
VERBOSE_PRINTK_STRING("Stopping rcu_torture_barrier task");
|
||||
kthread_stop(barrier_task);
|
||||
barrier_task = NULL;
|
||||
}
|
||||
if (barrier_cbs_tasks != NULL) {
|
||||
for (i = 0; i < n_barrier_cbs; i++) {
|
||||
if (barrier_cbs_tasks[i] != NULL) {
|
||||
VERBOSE_PRINTK_STRING("Stopping rcu_torture_barrier_cbs task");
|
||||
kthread_stop(barrier_cbs_tasks[i]);
|
||||
barrier_cbs_tasks[i] = NULL;
|
||||
}
|
||||
}
|
||||
kfree(barrier_cbs_tasks);
|
||||
barrier_cbs_tasks = NULL;
|
||||
}
|
||||
if (barrier_cbs_wq != NULL) {
|
||||
kfree(barrier_cbs_wq);
|
||||
barrier_cbs_wq = NULL;
|
||||
}
|
||||
}
|
||||
|
||||
static int rcutorture_cpu_notify(struct notifier_block *self,
|
||||
|
|
@ -1598,6 +1808,7 @@ rcu_torture_cleanup(void)
|
|||
fullstop = FULLSTOP_RMMOD;
|
||||
mutex_unlock(&fullstop_mutex);
|
||||
unregister_reboot_notifier(&rcutorture_shutdown_nb);
|
||||
rcu_torture_barrier_cleanup();
|
||||
rcu_torture_stall_cleanup();
|
||||
if (stutter_task) {
|
||||
VERBOSE_PRINTK_STRING("Stopping rcu_torture_stutter task");
|
||||
|
|
@ -1665,6 +1876,7 @@ rcu_torture_cleanup(void)
|
|||
VERBOSE_PRINTK_STRING("Stopping rcu_torture_shutdown task");
|
||||
kthread_stop(shutdown_task);
|
||||
}
|
||||
shutdown_task = NULL;
|
||||
rcu_torture_onoff_cleanup();
|
||||
|
||||
/* Wait for all RCU callbacks to fire. */
|
||||
|
|
@ -1676,7 +1888,7 @@ rcu_torture_cleanup(void)
|
|||
|
||||
if (cur_ops->cleanup)
|
||||
cur_ops->cleanup();
|
||||
if (atomic_read(&n_rcu_torture_error))
|
||||
if (atomic_read(&n_rcu_torture_error) || n_rcu_torture_barrier_error)
|
||||
rcu_torture_print_module_parms(cur_ops, "End of test: FAILURE");
|
||||
else if (n_online_successes != n_online_attempts ||
|
||||
n_offline_successes != n_offline_attempts)
|
||||
|
|
@ -1692,10 +1904,12 @@ rcu_torture_init(void)
|
|||
int i;
|
||||
int cpu;
|
||||
int firsterr = 0;
|
||||
int retval;
|
||||
static struct rcu_torture_ops *torture_ops[] =
|
||||
{ &rcu_ops, &rcu_sync_ops, &rcu_expedited_ops,
|
||||
&rcu_bh_ops, &rcu_bh_sync_ops, &rcu_bh_expedited_ops,
|
||||
&srcu_ops, &srcu_raw_ops, &srcu_expedited_ops,
|
||||
&srcu_ops, &srcu_sync_ops, &srcu_raw_ops,
|
||||
&srcu_raw_sync_ops, &srcu_expedited_ops,
|
||||
&sched_ops, &sched_sync_ops, &sched_expedited_ops, };
|
||||
|
||||
mutex_lock(&fullstop_mutex);
|
||||
|
|
@ -1749,6 +1963,7 @@ rcu_torture_init(void)
|
|||
atomic_set(&n_rcu_torture_free, 0);
|
||||
atomic_set(&n_rcu_torture_mberror, 0);
|
||||
atomic_set(&n_rcu_torture_error, 0);
|
||||
n_rcu_torture_barrier_error = 0;
|
||||
n_rcu_torture_boost_ktrerror = 0;
|
||||
n_rcu_torture_boost_rterror = 0;
|
||||
n_rcu_torture_boost_failure = 0;
|
||||
|
|
@ -1872,7 +2087,6 @@ rcu_torture_init(void)
|
|||
test_boost_duration = 2;
|
||||
if ((test_boost == 1 && cur_ops->can_boost) ||
|
||||
test_boost == 2) {
|
||||
int retval;
|
||||
|
||||
boost_starttime = jiffies + test_boost_interval * HZ;
|
||||
register_cpu_notifier(&rcutorture_cpu_nb);
|
||||
|
|
@ -1897,9 +2111,22 @@ rcu_torture_init(void)
|
|||
goto unwind;
|
||||
}
|
||||
}
|
||||
rcu_torture_onoff_init();
|
||||
i = rcu_torture_onoff_init();
|
||||
if (i != 0) {
|
||||
firsterr = i;
|
||||
goto unwind;
|
||||
}
|
||||
register_reboot_notifier(&rcutorture_shutdown_nb);
|
||||
rcu_torture_stall_init();
|
||||
i = rcu_torture_stall_init();
|
||||
if (i != 0) {
|
||||
firsterr = i;
|
||||
goto unwind;
|
||||
}
|
||||
retval = rcu_torture_barrier_init();
|
||||
if (retval != 0) {
|
||||
firsterr = retval;
|
||||
goto unwind;
|
||||
}
|
||||
rcutorture_record_test_transition();
|
||||
mutex_unlock(&fullstop_mutex);
|
||||
return 0;
|
||||
|
|
|
|||
|
|
@ -201,7 +201,6 @@ void rcu_note_context_switch(int cpu)
|
|||
{
|
||||
trace_rcu_utilization("Start context switch");
|
||||
rcu_sched_qs(cpu);
|
||||
rcu_preempt_note_context_switch(cpu);
|
||||
trace_rcu_utilization("End context switch");
|
||||
}
|
||||
EXPORT_SYMBOL_GPL(rcu_note_context_switch);
|
||||
|
|
@ -1953,6 +1952,38 @@ void call_rcu_bh(struct rcu_head *head, void (*func)(struct rcu_head *rcu))
|
|||
}
|
||||
EXPORT_SYMBOL_GPL(call_rcu_bh);
|
||||
|
||||
/*
|
||||
* Because a context switch is a grace period for RCU-sched and RCU-bh,
|
||||
* any blocking grace-period wait automatically implies a grace period
|
||||
* if there is only one CPU online at any point time during execution
|
||||
* of either synchronize_sched() or synchronize_rcu_bh(). It is OK to
|
||||
* occasionally incorrectly indicate that there are multiple CPUs online
|
||||
* when there was in fact only one the whole time, as this just adds
|
||||
* some overhead: RCU still operates correctly.
|
||||
*
|
||||
* Of course, sampling num_online_cpus() with preemption enabled can
|
||||
* give erroneous results if there are concurrent CPU-hotplug operations.
|
||||
* For example, given a demonic sequence of preemptions in num_online_cpus()
|
||||
* and CPU-hotplug operations, there could be two or more CPUs online at
|
||||
* all times, but num_online_cpus() might well return one (or even zero).
|
||||
*
|
||||
* However, all such demonic sequences require at least one CPU-offline
|
||||
* operation. Furthermore, rcu_blocking_is_gp() giving the wrong answer
|
||||
* is only a problem if there is an RCU read-side critical section executing
|
||||
* throughout. But RCU-sched and RCU-bh read-side critical sections
|
||||
* disable either preemption or bh, which prevents a CPU from going offline.
|
||||
* Therefore, the only way that rcu_blocking_is_gp() can incorrectly return
|
||||
* that there is only one CPU when in fact there was more than one throughout
|
||||
* is when there were no RCU readers in the system. If there are no
|
||||
* RCU readers, the grace period by definition can be of zero length,
|
||||
* regardless of the number of online CPUs.
|
||||
*/
|
||||
static inline int rcu_blocking_is_gp(void)
|
||||
{
|
||||
might_sleep(); /* Check for RCU read-side critical section. */
|
||||
return num_online_cpus() <= 1;
|
||||
}
|
||||
|
||||
/**
|
||||
* synchronize_sched - wait until an rcu-sched grace period has elapsed.
|
||||
*
|
||||
|
|
@ -2543,7 +2574,7 @@ static void __init rcu_init_levelspread(struct rcu_state *rsp)
|
|||
|
||||
for (i = NUM_RCU_LVLS - 1; i > 0; i--)
|
||||
rsp->levelspread[i] = CONFIG_RCU_FANOUT;
|
||||
rsp->levelspread[0] = RCU_FANOUT_LEAF;
|
||||
rsp->levelspread[0] = CONFIG_RCU_FANOUT_LEAF;
|
||||
}
|
||||
#else /* #ifdef CONFIG_RCU_FANOUT_EXACT */
|
||||
static void __init rcu_init_levelspread(struct rcu_state *rsp)
|
||||
|
|
|
|||
|
|
@ -29,18 +29,14 @@
|
|||
#include <linux/seqlock.h>
|
||||
|
||||
/*
|
||||
* Define shape of hierarchy based on NR_CPUS and CONFIG_RCU_FANOUT.
|
||||
* Define shape of hierarchy based on NR_CPUS, CONFIG_RCU_FANOUT, and
|
||||
* CONFIG_RCU_FANOUT_LEAF.
|
||||
* In theory, it should be possible to add more levels straightforwardly.
|
||||
* In practice, this did work well going from three levels to four.
|
||||
* Of course, your mileage may vary.
|
||||
*/
|
||||
#define MAX_RCU_LVLS 4
|
||||
#if CONFIG_RCU_FANOUT > 16
|
||||
#define RCU_FANOUT_LEAF 16
|
||||
#else /* #if CONFIG_RCU_FANOUT > 16 */
|
||||
#define RCU_FANOUT_LEAF (CONFIG_RCU_FANOUT)
|
||||
#endif /* #else #if CONFIG_RCU_FANOUT > 16 */
|
||||
#define RCU_FANOUT_1 (RCU_FANOUT_LEAF)
|
||||
#define RCU_FANOUT_1 (CONFIG_RCU_FANOUT_LEAF)
|
||||
#define RCU_FANOUT_2 (RCU_FANOUT_1 * CONFIG_RCU_FANOUT)
|
||||
#define RCU_FANOUT_3 (RCU_FANOUT_2 * CONFIG_RCU_FANOUT)
|
||||
#define RCU_FANOUT_4 (RCU_FANOUT_3 * CONFIG_RCU_FANOUT)
|
||||
|
|
@ -434,7 +430,6 @@ DECLARE_PER_CPU(char, rcu_cpu_has_work);
|
|||
/* Forward declarations for rcutree_plugin.h */
|
||||
static void rcu_bootup_announce(void);
|
||||
long rcu_batches_completed(void);
|
||||
static void rcu_preempt_note_context_switch(int cpu);
|
||||
static int rcu_preempt_blocked_readers_cgp(struct rcu_node *rnp);
|
||||
#ifdef CONFIG_HOTPLUG_CPU
|
||||
static void rcu_report_unblock_qs_rnp(struct rcu_node *rnp,
|
||||
|
|
|
|||
|
|
@ -153,7 +153,7 @@ static void rcu_preempt_qs(int cpu)
|
|||
*
|
||||
* Caller must disable preemption.
|
||||
*/
|
||||
static void rcu_preempt_note_context_switch(int cpu)
|
||||
void rcu_preempt_note_context_switch(void)
|
||||
{
|
||||
struct task_struct *t = current;
|
||||
unsigned long flags;
|
||||
|
|
@ -164,7 +164,7 @@ static void rcu_preempt_note_context_switch(int cpu)
|
|||
(t->rcu_read_unlock_special & RCU_READ_UNLOCK_BLOCKED) == 0) {
|
||||
|
||||
/* Possibly blocking in an RCU read-side critical section. */
|
||||
rdp = per_cpu_ptr(rcu_preempt_state.rda, cpu);
|
||||
rdp = __this_cpu_ptr(rcu_preempt_state.rda);
|
||||
rnp = rdp->mynode;
|
||||
raw_spin_lock_irqsave(&rnp->lock, flags);
|
||||
t->rcu_read_unlock_special |= RCU_READ_UNLOCK_BLOCKED;
|
||||
|
|
@ -228,7 +228,7 @@ static void rcu_preempt_note_context_switch(int cpu)
|
|||
* means that we continue to block the current grace period.
|
||||
*/
|
||||
local_irq_save(flags);
|
||||
rcu_preempt_qs(cpu);
|
||||
rcu_preempt_qs(smp_processor_id());
|
||||
local_irq_restore(flags);
|
||||
}
|
||||
|
||||
|
|
@ -969,22 +969,6 @@ static void __init __rcu_init_preempt(void)
|
|||
rcu_init_one(&rcu_preempt_state, &rcu_preempt_data);
|
||||
}
|
||||
|
||||
/*
|
||||
* Check for a task exiting while in a preemptible-RCU read-side
|
||||
* critical section, clean up if so. No need to issue warnings,
|
||||
* as debug_check_no_locks_held() already does this if lockdep
|
||||
* is enabled.
|
||||
*/
|
||||
void exit_rcu(void)
|
||||
{
|
||||
struct task_struct *t = current;
|
||||
|
||||
if (t->rcu_read_lock_nesting == 0)
|
||||
return;
|
||||
t->rcu_read_lock_nesting = 1;
|
||||
__rcu_read_unlock();
|
||||
}
|
||||
|
||||
#else /* #ifdef CONFIG_TREE_PREEMPT_RCU */
|
||||
|
||||
static struct rcu_state *rcu_state = &rcu_sched_state;
|
||||
|
|
@ -1017,14 +1001,6 @@ void rcu_force_quiescent_state(void)
|
|||
}
|
||||
EXPORT_SYMBOL_GPL(rcu_force_quiescent_state);
|
||||
|
||||
/*
|
||||
* Because preemptible RCU does not exist, we never have to check for
|
||||
* CPUs being in quiescent states.
|
||||
*/
|
||||
static void rcu_preempt_note_context_switch(int cpu)
|
||||
{
|
||||
}
|
||||
|
||||
/*
|
||||
* Because preemptible RCU does not exist, there are never any preempted
|
||||
* RCU readers.
|
||||
|
|
|
|||
|
|
@ -2083,6 +2083,7 @@ context_switch(struct rq *rq, struct task_struct *prev,
|
|||
#endif
|
||||
|
||||
/* Here we just switch the register state and the stack. */
|
||||
rcu_switch_from(prev);
|
||||
switch_to(prev, next, prev);
|
||||
|
||||
barrier();
|
||||
|
|
|
|||
548
kernel/srcu.c
548
kernel/srcu.c
|
|
@ -34,10 +34,77 @@
|
|||
#include <linux/delay.h>
|
||||
#include <linux/srcu.h>
|
||||
|
||||
/*
|
||||
* Initialize an rcu_batch structure to empty.
|
||||
*/
|
||||
static inline void rcu_batch_init(struct rcu_batch *b)
|
||||
{
|
||||
b->head = NULL;
|
||||
b->tail = &b->head;
|
||||
}
|
||||
|
||||
/*
|
||||
* Enqueue a callback onto the tail of the specified rcu_batch structure.
|
||||
*/
|
||||
static inline void rcu_batch_queue(struct rcu_batch *b, struct rcu_head *head)
|
||||
{
|
||||
*b->tail = head;
|
||||
b->tail = &head->next;
|
||||
}
|
||||
|
||||
/*
|
||||
* Is the specified rcu_batch structure empty?
|
||||
*/
|
||||
static inline bool rcu_batch_empty(struct rcu_batch *b)
|
||||
{
|
||||
return b->tail == &b->head;
|
||||
}
|
||||
|
||||
/*
|
||||
* Remove the callback at the head of the specified rcu_batch structure
|
||||
* and return a pointer to it, or return NULL if the structure is empty.
|
||||
*/
|
||||
static inline struct rcu_head *rcu_batch_dequeue(struct rcu_batch *b)
|
||||
{
|
||||
struct rcu_head *head;
|
||||
|
||||
if (rcu_batch_empty(b))
|
||||
return NULL;
|
||||
|
||||
head = b->head;
|
||||
b->head = head->next;
|
||||
if (b->tail == &head->next)
|
||||
rcu_batch_init(b);
|
||||
|
||||
return head;
|
||||
}
|
||||
|
||||
/*
|
||||
* Move all callbacks from the rcu_batch structure specified by "from" to
|
||||
* the structure specified by "to".
|
||||
*/
|
||||
static inline void rcu_batch_move(struct rcu_batch *to, struct rcu_batch *from)
|
||||
{
|
||||
if (!rcu_batch_empty(from)) {
|
||||
*to->tail = from->head;
|
||||
to->tail = from->tail;
|
||||
rcu_batch_init(from);
|
||||
}
|
||||
}
|
||||
|
||||
/* single-thread state-machine */
|
||||
static void process_srcu(struct work_struct *work);
|
||||
|
||||
static int init_srcu_struct_fields(struct srcu_struct *sp)
|
||||
{
|
||||
sp->completed = 0;
|
||||
mutex_init(&sp->mutex);
|
||||
spin_lock_init(&sp->queue_lock);
|
||||
sp->running = false;
|
||||
rcu_batch_init(&sp->batch_queue);
|
||||
rcu_batch_init(&sp->batch_check0);
|
||||
rcu_batch_init(&sp->batch_check1);
|
||||
rcu_batch_init(&sp->batch_done);
|
||||
INIT_DELAYED_WORK(&sp->work, process_srcu);
|
||||
sp->per_cpu_ref = alloc_percpu(struct srcu_struct_array);
|
||||
return sp->per_cpu_ref ? 0 : -ENOMEM;
|
||||
}
|
||||
|
|
@ -73,21 +140,116 @@ EXPORT_SYMBOL_GPL(init_srcu_struct);
|
|||
#endif /* #else #ifdef CONFIG_DEBUG_LOCK_ALLOC */
|
||||
|
||||
/*
|
||||
* srcu_readers_active_idx -- returns approximate number of readers
|
||||
* active on the specified rank of per-CPU counters.
|
||||
* Returns approximate total of the readers' ->seq[] values for the
|
||||
* rank of per-CPU counters specified by idx.
|
||||
*/
|
||||
|
||||
static int srcu_readers_active_idx(struct srcu_struct *sp, int idx)
|
||||
static unsigned long srcu_readers_seq_idx(struct srcu_struct *sp, int idx)
|
||||
{
|
||||
int cpu;
|
||||
int sum;
|
||||
unsigned long sum = 0;
|
||||
unsigned long t;
|
||||
|
||||
sum = 0;
|
||||
for_each_possible_cpu(cpu)
|
||||
sum += per_cpu_ptr(sp->per_cpu_ref, cpu)->c[idx];
|
||||
for_each_possible_cpu(cpu) {
|
||||
t = ACCESS_ONCE(per_cpu_ptr(sp->per_cpu_ref, cpu)->seq[idx]);
|
||||
sum += t;
|
||||
}
|
||||
return sum;
|
||||
}
|
||||
|
||||
/*
|
||||
* Returns approximate number of readers active on the specified rank
|
||||
* of the per-CPU ->c[] counters.
|
||||
*/
|
||||
static unsigned long srcu_readers_active_idx(struct srcu_struct *sp, int idx)
|
||||
{
|
||||
int cpu;
|
||||
unsigned long sum = 0;
|
||||
unsigned long t;
|
||||
|
||||
for_each_possible_cpu(cpu) {
|
||||
t = ACCESS_ONCE(per_cpu_ptr(sp->per_cpu_ref, cpu)->c[idx]);
|
||||
sum += t;
|
||||
}
|
||||
return sum;
|
||||
}
|
||||
|
||||
/*
|
||||
* Return true if the number of pre-existing readers is determined to
|
||||
* be stably zero. An example unstable zero can occur if the call
|
||||
* to srcu_readers_active_idx() misses an __srcu_read_lock() increment,
|
||||
* but due to task migration, sees the corresponding __srcu_read_unlock()
|
||||
* decrement. This can happen because srcu_readers_active_idx() takes
|
||||
* time to sum the array, and might in fact be interrupted or preempted
|
||||
* partway through the summation.
|
||||
*/
|
||||
static bool srcu_readers_active_idx_check(struct srcu_struct *sp, int idx)
|
||||
{
|
||||
unsigned long seq;
|
||||
|
||||
seq = srcu_readers_seq_idx(sp, idx);
|
||||
|
||||
/*
|
||||
* The following smp_mb() A pairs with the smp_mb() B located in
|
||||
* __srcu_read_lock(). This pairing ensures that if an
|
||||
* __srcu_read_lock() increments its counter after the summation
|
||||
* in srcu_readers_active_idx(), then the corresponding SRCU read-side
|
||||
* critical section will see any changes made prior to the start
|
||||
* of the current SRCU grace period.
|
||||
*
|
||||
* Also, if the above call to srcu_readers_seq_idx() saw the
|
||||
* increment of ->seq[], then the call to srcu_readers_active_idx()
|
||||
* must see the increment of ->c[].
|
||||
*/
|
||||
smp_mb(); /* A */
|
||||
|
||||
/*
|
||||
* Note that srcu_readers_active_idx() can incorrectly return
|
||||
* zero even though there is a pre-existing reader throughout.
|
||||
* To see this, suppose that task A is in a very long SRCU
|
||||
* read-side critical section that started on CPU 0, and that
|
||||
* no other reader exists, so that the sum of the counters
|
||||
* is equal to one. Then suppose that task B starts executing
|
||||
* srcu_readers_active_idx(), summing up to CPU 1, and then that
|
||||
* task C starts reading on CPU 0, so that its increment is not
|
||||
* summed, but finishes reading on CPU 2, so that its decrement
|
||||
* -is- summed. Then when task B completes its sum, it will
|
||||
* incorrectly get zero, despite the fact that task A has been
|
||||
* in its SRCU read-side critical section the whole time.
|
||||
*
|
||||
* We therefore do a validation step should srcu_readers_active_idx()
|
||||
* return zero.
|
||||
*/
|
||||
if (srcu_readers_active_idx(sp, idx) != 0)
|
||||
return false;
|
||||
|
||||
/*
|
||||
* The remainder of this function is the validation step.
|
||||
* The following smp_mb() D pairs with the smp_mb() C in
|
||||
* __srcu_read_unlock(). If the __srcu_read_unlock() was seen
|
||||
* by srcu_readers_active_idx() above, then any destructive
|
||||
* operation performed after the grace period will happen after
|
||||
* the corresponding SRCU read-side critical section.
|
||||
*
|
||||
* Note that there can be at most NR_CPUS worth of readers using
|
||||
* the old index, which is not enough to overflow even a 32-bit
|
||||
* integer. (Yes, this does mean that systems having more than
|
||||
* a billion or so CPUs need to be 64-bit systems.) Therefore,
|
||||
* the sum of the ->seq[] counters cannot possibly overflow.
|
||||
* Therefore, the only way that the return values of the two
|
||||
* calls to srcu_readers_seq_idx() can be equal is if there were
|
||||
* no increments of the corresponding rank of ->seq[] counts
|
||||
* in the interim. But the missed-increment scenario laid out
|
||||
* above includes an increment of the ->seq[] counter by
|
||||
* the corresponding __srcu_read_lock(). Therefore, if this
|
||||
* scenario occurs, the return values from the two calls to
|
||||
* srcu_readers_seq_idx() will differ, and thus the validation
|
||||
* step below suffices.
|
||||
*/
|
||||
smp_mb(); /* D */
|
||||
|
||||
return srcu_readers_seq_idx(sp, idx) == seq;
|
||||
}
|
||||
|
||||
/**
|
||||
* srcu_readers_active - returns approximate number of readers.
|
||||
* @sp: which srcu_struct to count active readers (holding srcu_read_lock).
|
||||
|
|
@ -98,7 +260,14 @@ static int srcu_readers_active_idx(struct srcu_struct *sp, int idx)
|
|||
*/
|
||||
static int srcu_readers_active(struct srcu_struct *sp)
|
||||
{
|
||||
return srcu_readers_active_idx(sp, 0) + srcu_readers_active_idx(sp, 1);
|
||||
int cpu;
|
||||
unsigned long sum = 0;
|
||||
|
||||
for_each_possible_cpu(cpu) {
|
||||
sum += ACCESS_ONCE(per_cpu_ptr(sp->per_cpu_ref, cpu)->c[0]);
|
||||
sum += ACCESS_ONCE(per_cpu_ptr(sp->per_cpu_ref, cpu)->c[1]);
|
||||
}
|
||||
return sum;
|
||||
}
|
||||
|
||||
/**
|
||||
|
|
@ -131,10 +300,11 @@ int __srcu_read_lock(struct srcu_struct *sp)
|
|||
int idx;
|
||||
|
||||
preempt_disable();
|
||||
idx = sp->completed & 0x1;
|
||||
barrier(); /* ensure compiler looks -once- at sp->completed. */
|
||||
per_cpu_ptr(sp->per_cpu_ref, smp_processor_id())->c[idx]++;
|
||||
srcu_barrier(); /* ensure compiler won't misorder critical section. */
|
||||
idx = rcu_dereference_index_check(sp->completed,
|
||||
rcu_read_lock_sched_held()) & 0x1;
|
||||
ACCESS_ONCE(this_cpu_ptr(sp->per_cpu_ref)->c[idx]) += 1;
|
||||
smp_mb(); /* B */ /* Avoid leaking the critical section. */
|
||||
ACCESS_ONCE(this_cpu_ptr(sp->per_cpu_ref)->seq[idx]) += 1;
|
||||
preempt_enable();
|
||||
return idx;
|
||||
}
|
||||
|
|
@ -149,8 +319,8 @@ EXPORT_SYMBOL_GPL(__srcu_read_lock);
|
|||
void __srcu_read_unlock(struct srcu_struct *sp, int idx)
|
||||
{
|
||||
preempt_disable();
|
||||
srcu_barrier(); /* ensure compiler won't misorder critical section. */
|
||||
per_cpu_ptr(sp->per_cpu_ref, smp_processor_id())->c[idx]--;
|
||||
smp_mb(); /* C */ /* Avoid leaking the critical section. */
|
||||
ACCESS_ONCE(this_cpu_ptr(sp->per_cpu_ref)->c[idx]) -= 1;
|
||||
preempt_enable();
|
||||
}
|
||||
EXPORT_SYMBOL_GPL(__srcu_read_unlock);
|
||||
|
|
@ -163,14 +333,86 @@ EXPORT_SYMBOL_GPL(__srcu_read_unlock);
|
|||
* we repeatedly block for 1-millisecond time periods. This approach
|
||||
* has done well in testing, so there is no need for a config parameter.
|
||||
*/
|
||||
#define SYNCHRONIZE_SRCU_READER_DELAY 10
|
||||
#define SRCU_RETRY_CHECK_DELAY 5
|
||||
#define SYNCHRONIZE_SRCU_TRYCOUNT 2
|
||||
#define SYNCHRONIZE_SRCU_EXP_TRYCOUNT 12
|
||||
|
||||
/*
|
||||
* @@@ Wait until all pre-existing readers complete. Such readers
|
||||
* will have used the index specified by "idx".
|
||||
* the caller should ensures the ->completed is not changed while checking
|
||||
* and idx = (->completed & 1) ^ 1
|
||||
*/
|
||||
static bool try_check_zero(struct srcu_struct *sp, int idx, int trycount)
|
||||
{
|
||||
for (;;) {
|
||||
if (srcu_readers_active_idx_check(sp, idx))
|
||||
return true;
|
||||
if (--trycount <= 0)
|
||||
return false;
|
||||
udelay(SRCU_RETRY_CHECK_DELAY);
|
||||
}
|
||||
}
|
||||
|
||||
/*
|
||||
* Increment the ->completed counter so that future SRCU readers will
|
||||
* use the other rank of the ->c[] and ->seq[] arrays. This allows
|
||||
* us to wait for pre-existing readers in a starvation-free manner.
|
||||
*/
|
||||
static void srcu_flip(struct srcu_struct *sp)
|
||||
{
|
||||
sp->completed++;
|
||||
}
|
||||
|
||||
/*
|
||||
* Enqueue an SRCU callback on the specified srcu_struct structure,
|
||||
* initiating grace-period processing if it is not already running.
|
||||
*/
|
||||
void call_srcu(struct srcu_struct *sp, struct rcu_head *head,
|
||||
void (*func)(struct rcu_head *head))
|
||||
{
|
||||
unsigned long flags;
|
||||
|
||||
head->next = NULL;
|
||||
head->func = func;
|
||||
spin_lock_irqsave(&sp->queue_lock, flags);
|
||||
rcu_batch_queue(&sp->batch_queue, head);
|
||||
if (!sp->running) {
|
||||
sp->running = true;
|
||||
queue_delayed_work(system_nrt_wq, &sp->work, 0);
|
||||
}
|
||||
spin_unlock_irqrestore(&sp->queue_lock, flags);
|
||||
}
|
||||
EXPORT_SYMBOL_GPL(call_srcu);
|
||||
|
||||
struct rcu_synchronize {
|
||||
struct rcu_head head;
|
||||
struct completion completion;
|
||||
};
|
||||
|
||||
/*
|
||||
* Awaken the corresponding synchronize_srcu() instance now that a
|
||||
* grace period has elapsed.
|
||||
*/
|
||||
static void wakeme_after_rcu(struct rcu_head *head)
|
||||
{
|
||||
struct rcu_synchronize *rcu;
|
||||
|
||||
rcu = container_of(head, struct rcu_synchronize, head);
|
||||
complete(&rcu->completion);
|
||||
}
|
||||
|
||||
static void srcu_advance_batches(struct srcu_struct *sp, int trycount);
|
||||
static void srcu_reschedule(struct srcu_struct *sp);
|
||||
|
||||
/*
|
||||
* Helper function for synchronize_srcu() and synchronize_srcu_expedited().
|
||||
*/
|
||||
static void __synchronize_srcu(struct srcu_struct *sp, void (*sync_func)(void))
|
||||
static void __synchronize_srcu(struct srcu_struct *sp, int trycount)
|
||||
{
|
||||
int idx;
|
||||
struct rcu_synchronize rcu;
|
||||
struct rcu_head *head = &rcu.head;
|
||||
bool done = false;
|
||||
|
||||
rcu_lockdep_assert(!lock_is_held(&sp->dep_map) &&
|
||||
!lock_is_held(&rcu_bh_lock_map) &&
|
||||
|
|
@ -178,91 +420,32 @@ static void __synchronize_srcu(struct srcu_struct *sp, void (*sync_func)(void))
|
|||
!lock_is_held(&rcu_sched_lock_map),
|
||||
"Illegal synchronize_srcu() in same-type SRCU (or RCU) read-side critical section");
|
||||
|
||||
idx = sp->completed;
|
||||
mutex_lock(&sp->mutex);
|
||||
init_completion(&rcu.completion);
|
||||
|
||||
/*
|
||||
* Check to see if someone else did the work for us while we were
|
||||
* waiting to acquire the lock. We need -two- advances of
|
||||
* the counter, not just one. If there was but one, we might have
|
||||
* shown up -after- our helper's first synchronize_sched(), thus
|
||||
* having failed to prevent CPU-reordering races with concurrent
|
||||
* srcu_read_unlock()s on other CPUs (see comment below). So we
|
||||
* either (1) wait for two or (2) supply the second ourselves.
|
||||
*/
|
||||
head->next = NULL;
|
||||
head->func = wakeme_after_rcu;
|
||||
spin_lock_irq(&sp->queue_lock);
|
||||
if (!sp->running) {
|
||||
/* steal the processing owner */
|
||||
sp->running = true;
|
||||
rcu_batch_queue(&sp->batch_check0, head);
|
||||
spin_unlock_irq(&sp->queue_lock);
|
||||
|
||||
if ((sp->completed - idx) >= 2) {
|
||||
mutex_unlock(&sp->mutex);
|
||||
return;
|
||||
srcu_advance_batches(sp, trycount);
|
||||
if (!rcu_batch_empty(&sp->batch_done)) {
|
||||
BUG_ON(sp->batch_done.head != head);
|
||||
rcu_batch_dequeue(&sp->batch_done);
|
||||
done = true;
|
||||
}
|
||||
/* give the processing owner to work_struct */
|
||||
srcu_reschedule(sp);
|
||||
} else {
|
||||
rcu_batch_queue(&sp->batch_queue, head);
|
||||
spin_unlock_irq(&sp->queue_lock);
|
||||
}
|
||||
|
||||
sync_func(); /* Force memory barrier on all CPUs. */
|
||||
|
||||
/*
|
||||
* The preceding synchronize_sched() ensures that any CPU that
|
||||
* sees the new value of sp->completed will also see any preceding
|
||||
* changes to data structures made by this CPU. This prevents
|
||||
* some other CPU from reordering the accesses in its SRCU
|
||||
* read-side critical section to precede the corresponding
|
||||
* srcu_read_lock() -- ensuring that such references will in
|
||||
* fact be protected.
|
||||
*
|
||||
* So it is now safe to do the flip.
|
||||
*/
|
||||
|
||||
idx = sp->completed & 0x1;
|
||||
sp->completed++;
|
||||
|
||||
sync_func(); /* Force memory barrier on all CPUs. */
|
||||
|
||||
/*
|
||||
* At this point, because of the preceding synchronize_sched(),
|
||||
* all srcu_read_lock() calls using the old counters have completed.
|
||||
* Their corresponding critical sections might well be still
|
||||
* executing, but the srcu_read_lock() primitives themselves
|
||||
* will have finished executing. We initially give readers
|
||||
* an arbitrarily chosen 10 microseconds to get out of their
|
||||
* SRCU read-side critical sections, then loop waiting 1/HZ
|
||||
* seconds per iteration. The 10-microsecond value has done
|
||||
* very well in testing.
|
||||
*/
|
||||
|
||||
if (srcu_readers_active_idx(sp, idx))
|
||||
udelay(SYNCHRONIZE_SRCU_READER_DELAY);
|
||||
while (srcu_readers_active_idx(sp, idx))
|
||||
schedule_timeout_interruptible(1);
|
||||
|
||||
sync_func(); /* Force memory barrier on all CPUs. */
|
||||
|
||||
/*
|
||||
* The preceding synchronize_sched() forces all srcu_read_unlock()
|
||||
* primitives that were executing concurrently with the preceding
|
||||
* for_each_possible_cpu() loop to have completed by this point.
|
||||
* More importantly, it also forces the corresponding SRCU read-side
|
||||
* critical sections to have also completed, and the corresponding
|
||||
* references to SRCU-protected data items to be dropped.
|
||||
*
|
||||
* Note:
|
||||
*
|
||||
* Despite what you might think at first glance, the
|
||||
* preceding synchronize_sched() -must- be within the
|
||||
* critical section ended by the following mutex_unlock().
|
||||
* Otherwise, a task taking the early exit can race
|
||||
* with a srcu_read_unlock(), which might have executed
|
||||
* just before the preceding srcu_readers_active() check,
|
||||
* and whose CPU might have reordered the srcu_read_unlock()
|
||||
* with the preceding critical section. In this case, there
|
||||
* is nothing preventing the synchronize_sched() task that is
|
||||
* taking the early exit from freeing a data structure that
|
||||
* is still being referenced (out of order) by the task
|
||||
* doing the srcu_read_unlock().
|
||||
*
|
||||
* Alternatively, the comparison with "2" on the early exit
|
||||
* could be changed to "3", but this increases synchronize_srcu()
|
||||
* latency for bulk loads. So the current code is preferred.
|
||||
*/
|
||||
|
||||
mutex_unlock(&sp->mutex);
|
||||
if (!done)
|
||||
wait_for_completion(&rcu.completion);
|
||||
}
|
||||
|
||||
/**
|
||||
|
|
@ -281,7 +464,7 @@ static void __synchronize_srcu(struct srcu_struct *sp, void (*sync_func)(void))
|
|||
*/
|
||||
void synchronize_srcu(struct srcu_struct *sp)
|
||||
{
|
||||
__synchronize_srcu(sp, synchronize_sched);
|
||||
__synchronize_srcu(sp, SYNCHRONIZE_SRCU_TRYCOUNT);
|
||||
}
|
||||
EXPORT_SYMBOL_GPL(synchronize_srcu);
|
||||
|
||||
|
|
@ -289,18 +472,11 @@ EXPORT_SYMBOL_GPL(synchronize_srcu);
|
|||
* synchronize_srcu_expedited - Brute-force SRCU grace period
|
||||
* @sp: srcu_struct with which to synchronize.
|
||||
*
|
||||
* Wait for an SRCU grace period to elapse, but use a "big hammer"
|
||||
* approach to force the grace period to end quickly. This consumes
|
||||
* significant time on all CPUs and is unfriendly to real-time workloads,
|
||||
* so is thus not recommended for any sort of common-case code. In fact,
|
||||
* if you are using synchronize_srcu_expedited() in a loop, please
|
||||
* restructure your code to batch your updates, and then use a single
|
||||
* synchronize_srcu() instead.
|
||||
* Wait for an SRCU grace period to elapse, but be more aggressive about
|
||||
* spinning rather than blocking when waiting.
|
||||
*
|
||||
* Note that it is illegal to call this function while holding any lock
|
||||
* that is acquired by a CPU-hotplug notifier. And yes, it is also illegal
|
||||
* to call this function from a CPU-hotplug notifier. Failing to observe
|
||||
* these restriction will result in deadlock. It is also illegal to call
|
||||
* that is acquired by a CPU-hotplug notifier. It is also illegal to call
|
||||
* synchronize_srcu_expedited() from the corresponding SRCU read-side
|
||||
* critical section; doing so will result in deadlock. However, it is
|
||||
* perfectly legal to call synchronize_srcu_expedited() on one srcu_struct
|
||||
|
|
@ -309,10 +485,19 @@ EXPORT_SYMBOL_GPL(synchronize_srcu);
|
|||
*/
|
||||
void synchronize_srcu_expedited(struct srcu_struct *sp)
|
||||
{
|
||||
__synchronize_srcu(sp, synchronize_sched_expedited);
|
||||
__synchronize_srcu(sp, SYNCHRONIZE_SRCU_EXP_TRYCOUNT);
|
||||
}
|
||||
EXPORT_SYMBOL_GPL(synchronize_srcu_expedited);
|
||||
|
||||
/**
|
||||
* srcu_barrier - Wait until all in-flight call_srcu() callbacks complete.
|
||||
*/
|
||||
void srcu_barrier(struct srcu_struct *sp)
|
||||
{
|
||||
synchronize_srcu(sp);
|
||||
}
|
||||
EXPORT_SYMBOL_GPL(srcu_barrier);
|
||||
|
||||
/**
|
||||
* srcu_batches_completed - return batches completed.
|
||||
* @sp: srcu_struct on which to report batch completion.
|
||||
|
|
@ -320,9 +505,146 @@ EXPORT_SYMBOL_GPL(synchronize_srcu_expedited);
|
|||
* Report the number of batches, correlated with, but not necessarily
|
||||
* precisely the same as, the number of grace periods that have elapsed.
|
||||
*/
|
||||
|
||||
long srcu_batches_completed(struct srcu_struct *sp)
|
||||
{
|
||||
return sp->completed;
|
||||
}
|
||||
EXPORT_SYMBOL_GPL(srcu_batches_completed);
|
||||
|
||||
#define SRCU_CALLBACK_BATCH 10
|
||||
#define SRCU_INTERVAL 1
|
||||
|
||||
/*
|
||||
* Move any new SRCU callbacks to the first stage of the SRCU grace
|
||||
* period pipeline.
|
||||
*/
|
||||
static void srcu_collect_new(struct srcu_struct *sp)
|
||||
{
|
||||
if (!rcu_batch_empty(&sp->batch_queue)) {
|
||||
spin_lock_irq(&sp->queue_lock);
|
||||
rcu_batch_move(&sp->batch_check0, &sp->batch_queue);
|
||||
spin_unlock_irq(&sp->queue_lock);
|
||||
}
|
||||
}
|
||||
|
||||
/*
|
||||
* Core SRCU state machine. Advance callbacks from ->batch_check0 to
|
||||
* ->batch_check1 and then to ->batch_done as readers drain.
|
||||
*/
|
||||
static void srcu_advance_batches(struct srcu_struct *sp, int trycount)
|
||||
{
|
||||
int idx = 1 ^ (sp->completed & 1);
|
||||
|
||||
/*
|
||||
* Because readers might be delayed for an extended period after
|
||||
* fetching ->completed for their index, at any point in time there
|
||||
* might well be readers using both idx=0 and idx=1. We therefore
|
||||
* need to wait for readers to clear from both index values before
|
||||
* invoking a callback.
|
||||
*/
|
||||
|
||||
if (rcu_batch_empty(&sp->batch_check0) &&
|
||||
rcu_batch_empty(&sp->batch_check1))
|
||||
return; /* no callbacks need to be advanced */
|
||||
|
||||
if (!try_check_zero(sp, idx, trycount))
|
||||
return; /* failed to advance, will try after SRCU_INTERVAL */
|
||||
|
||||
/*
|
||||
* The callbacks in ->batch_check1 have already done with their
|
||||
* first zero check and flip back when they were enqueued on
|
||||
* ->batch_check0 in a previous invocation of srcu_advance_batches().
|
||||
* (Presumably try_check_zero() returned false during that
|
||||
* invocation, leaving the callbacks stranded on ->batch_check1.)
|
||||
* They are therefore ready to invoke, so move them to ->batch_done.
|
||||
*/
|
||||
rcu_batch_move(&sp->batch_done, &sp->batch_check1);
|
||||
|
||||
if (rcu_batch_empty(&sp->batch_check0))
|
||||
return; /* no callbacks need to be advanced */
|
||||
srcu_flip(sp);
|
||||
|
||||
/*
|
||||
* The callbacks in ->batch_check0 just finished their
|
||||
* first check zero and flip, so move them to ->batch_check1
|
||||
* for future checking on the other idx.
|
||||
*/
|
||||
rcu_batch_move(&sp->batch_check1, &sp->batch_check0);
|
||||
|
||||
/*
|
||||
* SRCU read-side critical sections are normally short, so check
|
||||
* at least twice in quick succession after a flip.
|
||||
*/
|
||||
trycount = trycount < 2 ? 2 : trycount;
|
||||
if (!try_check_zero(sp, idx^1, trycount))
|
||||
return; /* failed to advance, will try after SRCU_INTERVAL */
|
||||
|
||||
/*
|
||||
* The callbacks in ->batch_check1 have now waited for all
|
||||
* pre-existing readers using both idx values. They are therefore
|
||||
* ready to invoke, so move them to ->batch_done.
|
||||
*/
|
||||
rcu_batch_move(&sp->batch_done, &sp->batch_check1);
|
||||
}
|
||||
|
||||
/*
|
||||
* Invoke a limited number of SRCU callbacks that have passed through
|
||||
* their grace period. If there are more to do, SRCU will reschedule
|
||||
* the workqueue.
|
||||
*/
|
||||
static void srcu_invoke_callbacks(struct srcu_struct *sp)
|
||||
{
|
||||
int i;
|
||||
struct rcu_head *head;
|
||||
|
||||
for (i = 0; i < SRCU_CALLBACK_BATCH; i++) {
|
||||
head = rcu_batch_dequeue(&sp->batch_done);
|
||||
if (!head)
|
||||
break;
|
||||
local_bh_disable();
|
||||
head->func(head);
|
||||
local_bh_enable();
|
||||
}
|
||||
}
|
||||
|
||||
/*
|
||||
* Finished one round of SRCU grace period. Start another if there are
|
||||
* more SRCU callbacks queued, otherwise put SRCU into not-running state.
|
||||
*/
|
||||
static void srcu_reschedule(struct srcu_struct *sp)
|
||||
{
|
||||
bool pending = true;
|
||||
|
||||
if (rcu_batch_empty(&sp->batch_done) &&
|
||||
rcu_batch_empty(&sp->batch_check1) &&
|
||||
rcu_batch_empty(&sp->batch_check0) &&
|
||||
rcu_batch_empty(&sp->batch_queue)) {
|
||||
spin_lock_irq(&sp->queue_lock);
|
||||
if (rcu_batch_empty(&sp->batch_done) &&
|
||||
rcu_batch_empty(&sp->batch_check1) &&
|
||||
rcu_batch_empty(&sp->batch_check0) &&
|
||||
rcu_batch_empty(&sp->batch_queue)) {
|
||||
sp->running = false;
|
||||
pending = false;
|
||||
}
|
||||
spin_unlock_irq(&sp->queue_lock);
|
||||
}
|
||||
|
||||
if (pending)
|
||||
queue_delayed_work(system_nrt_wq, &sp->work, SRCU_INTERVAL);
|
||||
}
|
||||
|
||||
/*
|
||||
* This is the work-queue function that handles SRCU grace periods.
|
||||
*/
|
||||
static void process_srcu(struct work_struct *work)
|
||||
{
|
||||
struct srcu_struct *sp;
|
||||
|
||||
sp = container_of(work, struct srcu_struct, work.work);
|
||||
|
||||
srcu_collect_new(sp);
|
||||
srcu_advance_batches(sp, 1);
|
||||
srcu_invoke_callbacks(sp);
|
||||
srcu_reschedule(sp);
|
||||
}
|
||||
|
|
|
|||
|
|
@ -861,7 +861,13 @@ EXPORT_SYMBOL(mod_timer);
|
|||
*
|
||||
* mod_timer_pinned() is a way to update the expire field of an
|
||||
* active timer (if the timer is inactive it will be activated)
|
||||
* and not allow the timer to be migrated to a different CPU.
|
||||
* and to ensure that the timer is scheduled on the current CPU.
|
||||
*
|
||||
* Note that this does not prevent the timer from being migrated
|
||||
* when the current CPU goes offline. If this is a problem for
|
||||
* you, use CPU-hotplug notifiers to handle it correctly, for
|
||||
* example, cancelling the timer when the corresponding CPU goes
|
||||
* offline.
|
||||
*
|
||||
* mod_timer_pinned(timer, expires) is equivalent to:
|
||||
*
|
||||
|
|
|
|||
|
|
@ -10,6 +10,7 @@
|
|||
#include <linux/list.h>
|
||||
#include <linux/bug.h>
|
||||
#include <linux/kernel.h>
|
||||
#include <linux/rculist.h>
|
||||
|
||||
/*
|
||||
* Insert a new entry between two known consecutive entries.
|
||||
|
|
@ -75,3 +76,24 @@ void list_del(struct list_head *entry)
|
|||
entry->prev = LIST_POISON2;
|
||||
}
|
||||
EXPORT_SYMBOL(list_del);
|
||||
|
||||
/*
|
||||
* RCU variants.
|
||||
*/
|
||||
void __list_add_rcu(struct list_head *new,
|
||||
struct list_head *prev, struct list_head *next)
|
||||
{
|
||||
WARN(next->prev != prev,
|
||||
"list_add_rcu corruption. next->prev should be "
|
||||
"prev (%p), but was %p. (next=%p).\n",
|
||||
prev, next->prev, next);
|
||||
WARN(prev->next != next,
|
||||
"list_add_rcu corruption. prev->next should be "
|
||||
"next (%p), but was %p. (prev=%p).\n",
|
||||
next, prev->next, prev);
|
||||
new->next = next;
|
||||
new->prev = prev;
|
||||
rcu_assign_pointer(list_next_rcu(prev), new);
|
||||
next->prev = new;
|
||||
}
|
||||
EXPORT_SYMBOL(__list_add_rcu);
|
||||
|
|
|
|||
Reference in New Issue