Commit-ID: b1f5b378e126133521df668379249fb8265121f1
Gitweb: https://git.kernel.org/tip/b1f5b378e126133521df668379249fb8265121f1
Author: Peter Zijlstra <[email protected]>
AuthorDate: Fri, 4 May 2018 11:11:42 +0200
Committer: Ingo Molnar <[email protected]>
CommitDate: Fri, 25 May 2018 08:03:51 +0200
kthread: Allow kthread_park() on a parked kthread
The following commit:
85f1abe0019f ("kthread, sched/wait: Fix kthread_parkme() completion issue")
added a WARN() in the case where we call kthread_park() on an already
parked thread, because the old code wasn't doing the right thing there
and it wasn't at all clear that would happen.
It turns out, this does in fact happen, so we have to deal with it.
Instead of potentially returning early, also wait for the completion.
This does however mean we have to use complete_all() and re-initialize
the completion on re-use.
Reported-by: LKP <[email protected]>
Tested-by: Meelis Roos <[email protected]>
Signed-off-by: Peter Zijlstra (Intel) <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: kernel test robot <[email protected]>
Cc: [email protected]
Cc: Thomas Gleixner <[email protected]>
Fixes: 85f1abe0019f ("kthread, sched/wait: Fix kthread_parkme() completion
issue")
Link:
http://lkml.kernel.org/r/[email protected]
Signed-off-by: Ingo Molnar <[email protected]>
---
kernel/kthread.c | 6 ++----
1 file changed, 2 insertions(+), 4 deletions(-)
diff --git a/kernel/kthread.c b/kernel/kthread.c
index 2017a39ab490..481951bf091d 100644
--- a/kernel/kthread.c
+++ b/kernel/kthread.c
@@ -193,7 +193,7 @@ EXPORT_SYMBOL_GPL(kthread_parkme);
void kthread_park_complete(struct task_struct *k)
{
- complete(&to_kthread(k)->parked);
+ complete_all(&to_kthread(k)->parked);
}
static int kthread(void *_create)
@@ -459,6 +459,7 @@ void kthread_unpark(struct task_struct *k)
if (test_bit(KTHREAD_IS_PER_CPU, &kthread->flags))
__kthread_bind(k, kthread->cpu, TASK_PARKED);
+ reinit_completion(&kthread->parked);
clear_bit(KTHREAD_SHOULD_PARK, &kthread->flags);
wake_up_state(k, TASK_PARKED);
}
@@ -483,9 +484,6 @@ int kthread_park(struct task_struct *k)
if (WARN_ON(k->flags & PF_EXITING))
return -ENOSYS;
- if (WARN_ON_ONCE(test_bit(KTHREAD_SHOULD_PARK, &kthread->flags)))
- return -EBUSY;
-
set_bit(KTHREAD_SHOULD_PARK, &kthread->flags);
if (k != current) {
wake_up_process(k);
