diff options
| author | Peter Zijlstra <peterz@infradead.org> | 2024-10-10 11:38:10 +0200 |
|---|---|---|
| committer | Ingo Molnar <mingo@kernel.org> | 2024-10-14 09:14:35 +0200 |
| commit | cd9626e9ebc77edec33023fe95dab4b04ffc819d (patch) | |
| tree | f634627362f80150130afc99ccda5cf58e584614 /kernel/freezer.c | |
| parent | c6508124193d42bbc3224571eb75bfa4c1821fbb (diff) | |
sched/fair: Fix external p->on_rq users
Sean noted that ever since commit 152e11f6df29 ("sched/fair: Implement
delayed dequeue") KVM's preemption notifiers have started
mis-classifying preemption vs blocking.
Notably p->on_rq is no longer sufficient to determine if a task is
runnable or blocked -- the aforementioned commit introduces tasks that
remain on the runqueue even through they will not run again, and
should be considered blocked for many cases.
Add the task_is_runnable() helper to classify things and audit all
external users of the p->on_rq state. Also add a few comments.
Fixes: 152e11f6df29 ("sched/fair: Implement delayed dequeue")
Reported-by: Sean Christopherson <seanjc@google.com>
Tested-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lkml.kernel.org/r/20241010091843.GK33184@noisy.programming.kicks-ass.net
Diffstat (limited to 'kernel/freezer.c')
| -rw-r--r-- | kernel/freezer.c | 7 |
1 files changed, 6 insertions, 1 deletions
diff --git a/kernel/freezer.c b/kernel/freezer.c index 44bbd7dbd2c8..8d530d0949ff 100644 --- a/kernel/freezer.c +++ b/kernel/freezer.c @@ -109,7 +109,12 @@ static int __set_task_frozen(struct task_struct *p, void *arg) { unsigned int state = READ_ONCE(p->__state); - if (p->on_rq) + /* + * Allow freezing the sched_delayed tasks; they will not execute until + * ttwu() fixes them up, so it is safe to swap their state now, instead + * of waiting for them to get fully dequeued. + */ + if (task_is_runnable(p)) return 0; if (p != current && task_curr(p)) |