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linux-2.6/block
Vivek Goyal dcf097b247 blk-cgroup: Fix RCU correctness warning in cfq_init_queue()
It is necessary to be in an RCU read-side critical section when invoking
css_id(), so this patch adds one to blkiocg_add_blkio_group().  This is
actually a false positive, because this is called at initialization time
and hence always refers to the root cgroup, which cannot go away.

[  103.790505] ===================================================
[  103.790509] [ INFO: suspicious rcu_dereference_check() usage. ]
[  103.790511] ---------------------------------------------------
[  103.790514] kernel/cgroup.c:4432 invoked rcu_dereference_check() without protection!
[  103.790517]
[  103.790517] other info that might help us debug this:
[  103.790519]
[  103.790521]
[  103.790521] rcu_scheduler_active = 1, debug_locks = 1
[  103.790524] 4 locks held by bash/4422:
[  103.790526]  #0:  (&buffer->mutex){+.+.+.}, at: [<ffffffff8114befa>] sysfs_write_file+0x3c/0x144
[  103.790537]  #1:  (s_active#102){.+.+.+}, at: [<ffffffff8114bfa5>] sysfs_write_file+0xe7/0x144
[  103.790544]  #2:  (&q->sysfs_lock){+.+.+.}, at: [<ffffffff812263b1>] queue_attr_store+0x49/0x8f
[  103.790552]  #3:  (&(&blkcg->lock)->rlock){......}, at: [<ffffffff8122e4db>] blkiocg_add_blkio_group+0x2b/0xad
[  103.790560]
[  103.790561] stack backtrace:
[  103.790564] Pid: 4422, comm: bash Not tainted 2.6.34-rc4-blkio-second-crash #81
[  103.790567] Call Trace:
[  103.790572]  [<ffffffff81068f57>] lockdep_rcu_dereference+0x9d/0xa5
[  103.790577]  [<ffffffff8107fac1>] css_id+0x44/0x57
[  103.790581]  [<ffffffff8122e503>] blkiocg_add_blkio_group+0x53/0xad
[  103.790586]  [<ffffffff81231936>] cfq_init_queue+0x139/0x32c
[  103.790591]  [<ffffffff8121f2d0>] elv_iosched_store+0xbf/0x1bf
[  103.790595]  [<ffffffff812263d8>] queue_attr_store+0x70/0x8f
[  103.790599]  [<ffffffff8114bfa5>] ? sysfs_write_file+0xe7/0x144
[  103.790603]  [<ffffffff8114bfc6>] sysfs_write_file+0x108/0x144
[  103.790609]  [<ffffffff810f527f>] vfs_write+0xae/0x10b
[  103.790612]  [<ffffffff81069863>] ? trace_hardirqs_on_caller+0x10c/0x130
[  103.790616]  [<ffffffff810f539c>] sys_write+0x4a/0x6e
[  103.790622]  [<ffffffff81002b5b>] system_call_fastpath+0x16/0x1b
[  103.790625]

Located-by: Miles Lane <miles.lane@gmail.com>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2010-05-06 08:54:00 +02:00
..
Kconfig block: make CONFIG_BLK_CGROUP visible 2010-03-16 08:57:15 +01:00
Kconfig.iosched cgroups: blkio subsystem as module 2010-03-12 15:52:36 -08:00
Makefile blkio: Introduce blkio controller cgroup interface 2009-12-03 19:28:51 +01:00
blk-barrier.c include cleanup: Update gfp.h and slab.h includes to prepare for breaking implicit slab.h inclusion from percpu.h 2010-03-30 22:02:32 +09:00
blk-cgroup.c include cleanup: Update gfp.h and slab.h includes to prepare for breaking implicit slab.h inclusion from percpu.h 2010-03-30 22:02:32 +09:00
blk-cgroup.h cgroups: blkio subsystem as module 2010-03-12 15:52:36 -08:00
blk-core.c block: Consolidate phys_segment and hw_segment limits 2010-02-26 13:58:08 +01:00
blk-exec.c block: don't set REQ_NOMERGE unnecessarily 2009-04-28 07:37:33 +02:00
blk-integrity.c include cleanup: Update gfp.h and slab.h includes to prepare for breaking implicit slab.h inclusion from percpu.h 2010-03-30 22:02:32 +09:00
blk-ioc.c include cleanup: Update gfp.h and slab.h includes to prepare for breaking implicit slab.h inclusion from percpu.h 2010-03-30 22:02:32 +09:00
blk-iopoll.c tree-wide: fix assorted typos all over the place 2009-12-04 15:39:55 +01:00
blk-map.c block: Use accessor functions for queue limits 2009-05-22 23:22:54 +02:00
blk-merge.c block: Consolidate phys_segment and hw_segment limits 2010-02-26 13:58:08 +01:00
blk-settings.c Merge branch 'for-linus' of git://git.kernel.dk/linux-2.6-block 2010-04-09 11:50:29 -07:00
blk-softirq.c generic-ipi: remove CSD_FLAG_WAIT 2009-02-25 14:13:44 +01:00
blk-sysfs.c Merge branch 'for-linus' of git://git.kernel.dk/linux-2.6-block 2010-04-09 11:50:29 -07:00
blk-tag.c include cleanup: Update gfp.h and slab.h includes to prepare for breaking implicit slab.h inclusion from percpu.h 2010-03-30 22:02:32 +09:00
blk-timeout.c block: ensure jiffies wrap is handled correctly in blk_rq_timed_out_timer 2010-04-21 17:42:08 +02:00
blk.h block: implement mixed merge of different failfast requests 2009-09-11 14:33:30 +02:00
bsg.c include cleanup: Update gfp.h and slab.h includes to prepare for breaking implicit slab.h inclusion from percpu.h 2010-03-30 22:02:32 +09:00
cfq-iosched.c blk-cgroup: Fix RCU correctness warning in cfq_init_queue() 2010-05-06 08:54:00 +02:00
compat_ioctl.c include cleanup: Update gfp.h and slab.h includes to prepare for breaking implicit slab.h inclusion from percpu.h 2010-03-30 22:02:32 +09:00
deadline-iosched.c block: convert to pos and nr_sectors accessors 2009-05-11 09:50:54 +02:00
elevator.c Block: Fix block/elevator.c elevator_get() off-by-one error 2010-04-02 08:41:14 +02:00
genhd.c block: Fix discard alignment calculation and printing 2010-01-11 14:29:19 +01:00
ioctl.c include cleanup: Update gfp.h and slab.h includes to prepare for breaking implicit slab.h inclusion from percpu.h 2010-03-30 22:02:32 +09:00
noop-iosched.c include cleanup: Update gfp.h and slab.h includes to prepare for breaking implicit slab.h inclusion from percpu.h 2010-03-30 22:02:32 +09:00
scsi_ioctl.c block/scsi_ioctl.c: quiet sparse noise 2009-11-04 09:10:33 +01:00