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sched_request_migrate(): fix race condition between migration req and IRQs

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make sure the caller thread holds migration queue lock with IRQs disabled
until it notifies the target CPU so that an interrupt can not deschedule
it in the middle of the request.

Change-Id: I85995018ca1e8478ccc9723985b6e8efc9c3acfb
This commit is contained in:
Balazs Gerofi
2019-12-27 12:22:49 +00:00
committed by Masamichi Takagi
parent 9e2196c9ce
commit 26bebb2749
1 changed files with 12 additions and 4 deletions
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16
kernel/process.c
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@ -3727,17 +3727,24 @@ void sched_request_migrate(int cpu_id, struct thread *thread)
unsigned long irqstate;
DECLARE_WAITQ_ENTRY_LOCKED(entry, cpu_local_var(current));
/*
* NOTES:
* - migration queue lock must be held before runqueue lock.
* - the lock must be held until migration request is added
* and the target core is notified, otherwise an interrupt
* may deschedule this thread and leave it hanging in
* uninterruptible state forever.
*/
irqstate = ihk_mc_spinlock_lock(&v->migq_lock);
waitq_init(&req.wq);
waitq_prepare_to_wait(&req.wq, &entry, PS_UNINTERRUPTIBLE);
irqstate = ihk_mc_spinlock_lock(&v->migq_lock);
list_add_tail(&req.list, &v->migq);
ihk_mc_spinlock_unlock(&v->migq_lock, irqstate);
irqstate = ihk_mc_spinlock_lock(&v->runq_lock);
ihk_mc_spinlock_lock_noirq(&v->runq_lock);
v->flags |= CPU_FLAG_NEED_RESCHED | CPU_FLAG_NEED_MIGRATE;
v->status = CPU_STATUS_RUNNING;
ihk_mc_spinlock_unlock(&v->runq_lock, irqstate);
ihk_mc_spinlock_unlock_noirq(&v->runq_lock);
if (cpu_id != ihk_mc_get_processor_id()) {
/* Kick scheduler */
@ -3746,6 +3753,7 @@ void sched_request_migrate(int cpu_id, struct thread *thread)
}
dkprintf("%s: tid: %d -> cpu: %d\n",
__FUNCTION__, thread->tid, cpu_id);
ihk_mc_spinlock_unlock(&v->migq_lock, irqstate);
schedule();
waitq_finish_wait(&req.wq, &entry);