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/rcu | |
| 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/rcu')
| -rw-r--r-- | kernel/rcu/tasks.h | 9 |
1 files changed, 9 insertions, 0 deletions
diff --git a/kernel/rcu/tasks.h b/kernel/rcu/tasks.h index 6333f4ccf024..4d7ee95df06e 100644 --- a/kernel/rcu/tasks.h +++ b/kernel/rcu/tasks.h @@ -986,6 +986,15 @@ static bool rcu_tasks_is_holdout(struct task_struct *t) return false; /* + * t->on_rq && !t->se.sched_delayed *could* be considered sleeping but + * since it is a spurious state (it will transition into the + * traditional blocked state or get woken up without outside + * dependencies), not considering it such should only affect timing. + * + * Be conservative for now and not include it. + */ + + /* * Idle tasks (or idle injection) within the idle loop are RCU-tasks * quiescent states. But CPU boot code performed by the idle task * isn't a quiescent state. |