sched: fix the theoretical signal_wake_up() vs schedule() race

[platform/adaptation/renesas_rcar/renesas_kernel.git] / kernel / sched / core.c

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index b7c32cb..ef51b0e 100644 (file)
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -1491,7 +1491,13 @@ try_to_wake_up(struct task_struct *p, unsigned int state, int wake_flags)
        unsigned long flags;
        int cpu, success = 0;
 
-       smp_wmb();
+       /*
+        * If we are going to wake up a thread waiting for CONDITION we
+        * need to ensure that CONDITION=1 done by the caller can not be
+        * reordered with p->state check below. This pairs with mb() in
+        * set_current_state() the waiting thread does.
+        */
+       smp_mb__before_spinlock();
        raw_spin_lock_irqsave(&p->pi_lock, flags);
        if (!(p->state & state))
                goto out;
@@ -2394,6 +2400,12 @@ need_resched:
        if (sched_feat(HRTICK))
                hrtick_clear(rq);
 
+       /*
+        * Make sure that signal_pending_state()->signal_pending() below
+        * can't be reordered with __set_current_state(TASK_INTERRUPTIBLE)
+        * done by the caller to avoid the race with signal_wake_up().
+        */
+       smp_mb__before_spinlock();
        raw_spin_lock_irq(&rq->lock);
 
        switch_count = &prev->nivcsw;