summaryrefslogtreecommitdiff
path: root/kernel
diff options
context:
space:
mode:
authorElliot Berman <quic_eberman@quicinc.com>2023-11-20 09:36:31 -0800
committerPeter Zijlstra <peterz@infradead.org>2023-11-29 15:43:48 +0100
commit23ab79e8e469e2605beec2e3ccb40d19c68dd2e0 (patch)
treed4464e5b0796942989b1753c7df8ce60856fe472 /kernel
parent2cc14f52aeb78ce3f29677c2de1f06c0e91471ab (diff)
freezer,sched: Do not restore saved_state of a thawed task
It is possible for a task to be thawed multiple times when mixing the *legacy* cgroup freezer and system-wide freezer. To do this, freeze the cgroup, do system-wide freeze/thaw, then thaw the cgroup. When this happens, then a stale saved_state can be written to the task's state and cause task to hang indefinitely. Fix this by only trying to thaw tasks that are actually frozen. This change also has the marginal benefit avoiding unnecessary wake_up_state(p, TASK_FROZEN) if we know the task is already thawed. There is not possibility of time-of-compare/time-of-use race when we skip the wake_up_state because entering/exiting TASK_FROZEN is guarded by freezer_lock. Fixes: 8f0eed4a78a8 ("freezer,sched: Use saved_state to reduce some spurious wakeups") Signed-off-by: Elliot Berman <quic_eberman@quicinc.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Reviewed-by: Abhijeet Dharmapurikar <quic_adharmap@quicinc.com> Link: https://lore.kernel.org/r/20231120-freezer-state-multiple-thaws-v1-1-f2e1dd7ce5a2@quicinc.com
Diffstat (limited to 'kernel')
-rw-r--r--kernel/freezer.c2
1 files changed, 1 insertions, 1 deletions
diff --git a/kernel/freezer.c b/kernel/freezer.c
index c450fa8b8b5e..759006a9a910 100644
--- a/kernel/freezer.c
+++ b/kernel/freezer.c
@@ -201,7 +201,7 @@ void __thaw_task(struct task_struct *p)
if (WARN_ON_ONCE(freezing(p)))
goto unlock;
- if (task_call_func(p, __restore_freezer_state, NULL))
+ if (!frozen(p) || task_call_func(p, __restore_freezer_state, NULL))
goto unlock;
wake_up_state(p, TASK_FROZEN);