e625397041
stop_two_cpus() and stop_cpus() use stop_cpus_lock to avoid the deadlock, we need to ensure that the stopper functions can't be queued "backwards" from one another. This doesn't look nice; if we use lglock then we do not really need stopper->lock, cpu_stop_queue_work() could use lg_local_lock() under local_irq_save(). OTOH it would be even better to avoid lglock in stop_machine.c and remove lg_double_lock(). This patch adds "bool stop_cpus_in_progress" set/cleared by queue_stop_cpus_work(), and changes cpu_stop_queue_two_works() to busy wait until it is cleared. queue_stop_cpus_work() sets stop_cpus_in_progress = T lockless, but after it queues a work on CPU1 it must be visible to stop_two_cpus(CPU1, CPU2) which checks it under the same lock. And since stop_two_cpus() holds the 2nd lock too, queue_stop_cpus_work() can not clear stop_cpus_in_progress if it is also going to queue a work on CPU2, it needs to take that 2nd lock to do this. Signed-off-by: Oleg Nesterov <oleg@redhat.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Rik van Riel <riel@redhat.com> Cc: Tejun Heo <tj@kernel.org> Cc: Thomas Gleixner <tglx@linutronix.de> Link: http://lkml.kernel.org/r/20151121181148.GA433@redhat.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
90 lines
1.9 KiB
C
90 lines
1.9 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_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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