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authorPeter Zijlstra <peterz@infradead.org>2018-05-04 11:11:42 +0200
committerIngo Molnar <mingo@kernel.org>2018-05-25 08:03:51 +0200
commitb1f5b378e126133521df668379249fb8265121f1 (patch)
treeee2ffdde3e7ca65a6090babe51ae1851411e0903
parentbf5015a50f1fdb248b48405b67cae24dc02605d6 (diff)
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 <lkp@01.org> Tested-by: Meelis Roos <mroos@linux.ee> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: kernel test robot <lkp@intel.com> Cc: wfg@linux.intel.com Cc: Thomas Gleixner <tglx@linutronix.de> Fixes: 85f1abe0019f ("kthread, sched/wait: Fix kthread_parkme() completion issue") Link: http://lkml.kernel.org/r/20180504091142.GI12235@hirez.programming.kicks-ass.net Signed-off-by: Ingo Molnar <mingo@kernel.org>
-rw-r--r--kernel/kthread.c6
1 files 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);