diff options
| -rw-r--r-- | kernel/sched/core.c | 24 |
1 files changed, 14 insertions, 10 deletions
diff --git a/kernel/sched/core.c b/kernel/sched/core.c index e15543cb8481..5dece9b34e25 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -4119,9 +4119,6 @@ static void __sched notrace __schedule(bool preempt) local_irq_disable(); rcu_note_context_switch(preempt); - /* See deactivate_task() below. */ - prev_state = prev->state; - /* * Make sure that signal_pending_state()->signal_pending() below * can't be reordered with __set_current_state(TASK_INTERRUPTIBLE) @@ -4145,11 +4142,16 @@ static void __sched notrace __schedule(bool preempt) update_rq_clock(rq); switch_count = &prev->nivcsw; + /* - * We must re-load prev->state in case ttwu_remote() changed it - * before we acquired rq->lock. + * We must load prev->state once (task_struct::state is volatile), such + * that: + * + * - we form a control dependency vs deactivate_task() below. + * - ptrace_{,un}freeze_traced() can change ->state underneath us. */ - if (!preempt && prev_state && prev_state == prev->state) { + prev_state = prev->state; + if (!preempt && prev_state) { if (signal_pending_state(prev_state, prev)) { prev->state = TASK_RUNNING; } else { @@ -4163,10 +4165,12 @@ static void __sched notrace __schedule(bool preempt) /* * __schedule() ttwu() - * prev_state = prev->state; if (READ_ONCE(p->on_rq) && ...) - * LOCK rq->lock goto out; - * smp_mb__after_spinlock(); smp_acquire__after_ctrl_dep(); - * p->on_rq = 0; p->state = TASK_WAKING; + * prev_state = prev->state; if (p->on_rq && ...) + * if (prev_state) goto out; + * p->on_rq = 0; smp_acquire__after_ctrl_dep(); + * p->state = TASK_WAKING + * + * Where __schedule() and ttwu() have matching control dependencies. * * After this, schedule() must not care about p->state any more. */ |