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b17718d02f
Jiri reported a machine stuck in multi_cpu_stop() with
migrate_swap_stop() as function and with the following src,dst cpu
pairs: {11, 4} {13, 11} { 4, 13}
4 11 13
cpuM: queue(4 ,13)
*Ma
cpuN: queue(13,11)
*N Na
*M Mb
cpuO: queue(11, 4)
*O Oa
*Nb
*Ob
Where *X denotes the cpu running the queueing of cpu-X and X[ab] denotes
the first/second queued work.
You'll observe the top of the workqueue for each cpu: 4,11,13 to be work
from cpus: M, O, N resp. IOW. deadlock.
Do away with the queueing trickery and introduce lg_double_lock() to
lock both CPUs and fully serialize the stop_two_cpus() callers instead
of the partial (and buggy) serialization we have now.
Reported-by: Jiri Olsa <jolsa@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/20150605153023.GH19282@twins.programming.kicks-ass.net
Signed-off-by: Ingo Molnar <mingo@kernel.org>
112 lines
2.5 KiB
C
112 lines
2.5 KiB
C
/* See include/linux/lglock.h for description */
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#include <linux/module.h>
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#include <linux/lglock.h>
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#include <linux/cpu.h>
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#include <linux/string.h>
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/*
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* Note there is no uninit, so lglocks cannot be defined in
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* modules (but it's fine to use them from there)
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* Could be added though, just undo lg_lock_init
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*/
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void lg_lock_init(struct lglock *lg, char *name)
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{
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LOCKDEP_INIT_MAP(&lg->lock_dep_map, name, &lg->lock_key, 0);
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}
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EXPORT_SYMBOL(lg_lock_init);
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void lg_local_lock(struct lglock *lg)
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{
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arch_spinlock_t *lock;
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preempt_disable();
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lock_acquire_shared(&lg->lock_dep_map, 0, 0, NULL, _RET_IP_);
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lock = this_cpu_ptr(lg->lock);
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arch_spin_lock(lock);
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}
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EXPORT_SYMBOL(lg_local_lock);
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void lg_local_unlock(struct lglock *lg)
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{
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arch_spinlock_t *lock;
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lock_release(&lg->lock_dep_map, 1, _RET_IP_);
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lock = this_cpu_ptr(lg->lock);
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arch_spin_unlock(lock);
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preempt_enable();
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}
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EXPORT_SYMBOL(lg_local_unlock);
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void lg_local_lock_cpu(struct lglock *lg, int cpu)
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{
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arch_spinlock_t *lock;
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preempt_disable();
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lock_acquire_shared(&lg->lock_dep_map, 0, 0, NULL, _RET_IP_);
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lock = per_cpu_ptr(lg->lock, cpu);
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arch_spin_lock(lock);
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}
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EXPORT_SYMBOL(lg_local_lock_cpu);
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void lg_local_unlock_cpu(struct lglock *lg, int cpu)
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{
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arch_spinlock_t *lock;
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lock_release(&lg->lock_dep_map, 1, _RET_IP_);
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lock = per_cpu_ptr(lg->lock, cpu);
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arch_spin_unlock(lock);
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preempt_enable();
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}
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EXPORT_SYMBOL(lg_local_unlock_cpu);
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void lg_double_lock(struct lglock *lg, int cpu1, int cpu2)
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{
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BUG_ON(cpu1 == cpu2);
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/* lock in cpu order, just like lg_global_lock */
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if (cpu2 < cpu1)
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swap(cpu1, cpu2);
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preempt_disable();
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lock_acquire_shared(&lg->lock_dep_map, 0, 0, NULL, _RET_IP_);
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arch_spin_lock(per_cpu_ptr(lg->lock, cpu1));
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arch_spin_lock(per_cpu_ptr(lg->lock, cpu2));
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}
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void lg_double_unlock(struct lglock *lg, int cpu1, int cpu2)
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{
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lock_release(&lg->lock_dep_map, 1, _RET_IP_);
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arch_spin_unlock(per_cpu_ptr(lg->lock, cpu1));
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arch_spin_unlock(per_cpu_ptr(lg->lock, cpu2));
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preempt_enable();
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}
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void lg_global_lock(struct lglock *lg)
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{
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int i;
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preempt_disable();
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lock_acquire_exclusive(&lg->lock_dep_map, 0, 0, NULL, _RET_IP_);
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for_each_possible_cpu(i) {
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arch_spinlock_t *lock;
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lock = per_cpu_ptr(lg->lock, i);
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arch_spin_lock(lock);
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}
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}
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EXPORT_SYMBOL(lg_global_lock);
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void lg_global_unlock(struct lglock *lg)
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{
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int i;
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lock_release(&lg->lock_dep_map, 1, _RET_IP_);
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for_each_possible_cpu(i) {
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arch_spinlock_t *lock;
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lock = per_cpu_ptr(lg->lock, i);
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arch_spin_unlock(lock);
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}
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preempt_enable();
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}
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EXPORT_SYMBOL(lg_global_unlock);
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