![Paul E. McKenney](/assets/img/avatar_default.png)
Fourth cut of patch to provide the call_rcu_sched(). This is again to synchronize_sched() as call_rcu() is to synchronize_rcu(). Should be fine for experimental and -rt use, but not ready for inclusion. With some luck, I will be able to tell Andrew to come out of hiding on the next round. Passes multi-day rcutorture sessions with concurrent CPU hotplugging. Fixes since the first version include a bug that could result in indefinite blocking (spotted by Gautham Shenoy), better resiliency against CPU-hotplug operations, and other minor fixes. Fixes since the second version include reworking grace-period detection to avoid deadlocks that could happen when running concurrently with CPU hotplug, adding Mathieu's fix to avoid the softlockup messages, as well as Mathieu's fix to allow use earlier in boot. Fixes since the third version include a wrong-CPU bug spotted by Andrew, getting rid of the obsolete synchronize_kernel API that somehow snuck back in, merging spin_unlock() and local_irq_restore() in a few places, commenting the code that checks for quiescent states based on interrupting from user-mode execution or the idle loop, removing some inline attributes, and some code-style changes. Known/suspected shortcomings: o I still do not entirely trust the sleep/wakeup logic. Next step will be to use a private snapshot of the CPU online mask in rcu_sched_grace_period() -- if the CPU wasn't there at the start of the grace period, we don't need to hear from it. And the bit about accounting for changes in online CPUs inside of rcu_sched_grace_period() is ugly anyway. o It might be good for rcu_sched_grace_period() to invoke resched_cpu() when a given CPU wasn't responding quickly, but resched_cpu() is declared static... This patch also fixes a long-standing bug in the earlier preemptable-RCU implementation of synchronize_rcu() that could result in loss of concurrent external changes to a task's CPU affinity mask. I still cannot remember who reported this... Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca> Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
168 lines
4.8 KiB
C
168 lines
4.8 KiB
C
/*
|
|
* Read-Copy Update mechanism for mutual exclusion (classic version)
|
|
*
|
|
* This program is free software; you can redistribute it and/or modify
|
|
* it under the terms of the GNU General Public License as published by
|
|
* the Free Software Foundation; either version 2 of the License, or
|
|
* (at your option) any later version.
|
|
*
|
|
* This program is distributed in the hope that it will be useful,
|
|
* but WITHOUT ANY WARRANTY; without even the implied warranty of
|
|
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
|
|
* GNU General Public License for more details.
|
|
*
|
|
* You should have received a copy of the GNU General Public License
|
|
* along with this program; if not, write to the Free Software
|
|
* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
|
|
*
|
|
* Copyright IBM Corporation, 2001
|
|
*
|
|
* Author: Dipankar Sarma <dipankar@in.ibm.com>
|
|
*
|
|
* Based on the original work by Paul McKenney <paulmck@us.ibm.com>
|
|
* and inputs from Rusty Russell, Andrea Arcangeli and Andi Kleen.
|
|
* Papers:
|
|
* http://www.rdrop.com/users/paulmck/paper/rclockpdcsproof.pdf
|
|
* http://lse.sourceforge.net/locking/rclock_OLS.2001.05.01c.sc.pdf (OLS2001)
|
|
*
|
|
* For detailed explanation of Read-Copy Update mechanism see -
|
|
* Documentation/RCU
|
|
*
|
|
*/
|
|
|
|
#ifndef __LINUX_RCUCLASSIC_H
|
|
#define __LINUX_RCUCLASSIC_H
|
|
|
|
#include <linux/cache.h>
|
|
#include <linux/spinlock.h>
|
|
#include <linux/threads.h>
|
|
#include <linux/percpu.h>
|
|
#include <linux/cpumask.h>
|
|
#include <linux/seqlock.h>
|
|
|
|
|
|
/* Global control variables for rcupdate callback mechanism. */
|
|
struct rcu_ctrlblk {
|
|
long cur; /* Current batch number. */
|
|
long completed; /* Number of the last completed batch */
|
|
int next_pending; /* Is the next batch already waiting? */
|
|
|
|
int signaled;
|
|
|
|
spinlock_t lock ____cacheline_internodealigned_in_smp;
|
|
cpumask_t cpumask; /* CPUs that need to switch in order */
|
|
/* for current batch to proceed. */
|
|
} ____cacheline_internodealigned_in_smp;
|
|
|
|
/* Is batch a before batch b ? */
|
|
static inline int rcu_batch_before(long a, long b)
|
|
{
|
|
return (a - b) < 0;
|
|
}
|
|
|
|
/* Is batch a after batch b ? */
|
|
static inline int rcu_batch_after(long a, long b)
|
|
{
|
|
return (a - b) > 0;
|
|
}
|
|
|
|
/*
|
|
* Per-CPU data for Read-Copy UPdate.
|
|
* nxtlist - new callbacks are added here
|
|
* curlist - current batch for which quiescent cycle started if any
|
|
*/
|
|
struct rcu_data {
|
|
/* 1) quiescent state handling : */
|
|
long quiescbatch; /* Batch # for grace period */
|
|
int passed_quiesc; /* User-mode/idle loop etc. */
|
|
int qs_pending; /* core waits for quiesc state */
|
|
|
|
/* 2) batch handling */
|
|
long batch; /* Batch # for current RCU batch */
|
|
struct rcu_head *nxtlist;
|
|
struct rcu_head **nxttail;
|
|
long qlen; /* # of queued callbacks */
|
|
struct rcu_head *curlist;
|
|
struct rcu_head **curtail;
|
|
struct rcu_head *donelist;
|
|
struct rcu_head **donetail;
|
|
long blimit; /* Upper limit on a processed batch */
|
|
int cpu;
|
|
struct rcu_head barrier;
|
|
};
|
|
|
|
DECLARE_PER_CPU(struct rcu_data, rcu_data);
|
|
DECLARE_PER_CPU(struct rcu_data, rcu_bh_data);
|
|
|
|
/*
|
|
* Increment the quiescent state counter.
|
|
* The counter is a bit degenerated: We do not need to know
|
|
* how many quiescent states passed, just if there was at least
|
|
* one since the start of the grace period. Thus just a flag.
|
|
*/
|
|
static inline void rcu_qsctr_inc(int cpu)
|
|
{
|
|
struct rcu_data *rdp = &per_cpu(rcu_data, cpu);
|
|
rdp->passed_quiesc = 1;
|
|
}
|
|
static inline void rcu_bh_qsctr_inc(int cpu)
|
|
{
|
|
struct rcu_data *rdp = &per_cpu(rcu_bh_data, cpu);
|
|
rdp->passed_quiesc = 1;
|
|
}
|
|
|
|
extern int rcu_pending(int cpu);
|
|
extern int rcu_needs_cpu(int cpu);
|
|
|
|
#ifdef CONFIG_DEBUG_LOCK_ALLOC
|
|
extern struct lockdep_map rcu_lock_map;
|
|
# define rcu_read_acquire() \
|
|
lock_acquire(&rcu_lock_map, 0, 0, 2, 1, _THIS_IP_)
|
|
# define rcu_read_release() lock_release(&rcu_lock_map, 1, _THIS_IP_)
|
|
#else
|
|
# define rcu_read_acquire() do { } while (0)
|
|
# define rcu_read_release() do { } while (0)
|
|
#endif
|
|
|
|
#define __rcu_read_lock() \
|
|
do { \
|
|
preempt_disable(); \
|
|
__acquire(RCU); \
|
|
rcu_read_acquire(); \
|
|
} while (0)
|
|
#define __rcu_read_unlock() \
|
|
do { \
|
|
rcu_read_release(); \
|
|
__release(RCU); \
|
|
preempt_enable(); \
|
|
} while (0)
|
|
#define __rcu_read_lock_bh() \
|
|
do { \
|
|
local_bh_disable(); \
|
|
__acquire(RCU_BH); \
|
|
rcu_read_acquire(); \
|
|
} while (0)
|
|
#define __rcu_read_unlock_bh() \
|
|
do { \
|
|
rcu_read_release(); \
|
|
__release(RCU_BH); \
|
|
local_bh_enable(); \
|
|
} while (0)
|
|
|
|
#define __synchronize_sched() synchronize_rcu()
|
|
|
|
#define call_rcu_sched(head, func) call_rcu(head, func)
|
|
|
|
extern void __rcu_init(void);
|
|
#define rcu_init_sched() do { } while (0)
|
|
extern void rcu_check_callbacks(int cpu, int user);
|
|
extern void rcu_restart_cpu(int cpu);
|
|
|
|
extern long rcu_batches_completed(void);
|
|
extern long rcu_batches_completed_bh(void);
|
|
|
|
#define rcu_enter_nohz() do { } while (0)
|
|
#define rcu_exit_nohz() do { } while (0)
|
|
|
|
#endif /* __LINUX_RCUCLASSIC_H */
|