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authorPeter Zijlstra <peterz@infradead.org>2014-10-31 11:57:30 +0100
committerIngo Molnar <mingo@kernel.org>2014-11-04 07:17:44 +0100
commitcb6538e740d7543cd989128625cf8cac4b471e0a (patch)
treec2b2c8d97c12fe06ead2f810471bd6f0317da2d0 /kernel/sched
parent3427445afd26bd2395f29241319283a93f362cd0 (diff)
sched/wait: Fix a kthread race with wait_woken()
There is a race between kthread_stop() and the new wait_woken() that can result in a lack of progress. CPU 0 | CPU 1 | rfcomm_run() | kthread_stop() ... | if (!test_bit(KTHREAD_SHOULD_STOP)) | | set_bit(KTHREAD_SHOULD_STOP) | wake_up_process() wait_woken() | wait_for_completion() set_current_state(INTERRUPTIBLE) | if (!WQ_FLAG_WOKEN) | schedule_timeout() | | After which both tasks will wait.. forever. Fix this by having wait_woken() check for kthread_should_stop() but only for kthreads (obviously). Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Peter Hurley <peter@hurleysoftware.com> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'kernel/sched')
-rw-r--r--kernel/sched/wait.c7
1 files changed, 6 insertions, 1 deletions
diff --git a/kernel/sched/wait.c b/kernel/sched/wait.c
index 4dae1885db6f..852143a79f36 100644
--- a/kernel/sched/wait.c
+++ b/kernel/sched/wait.c
@@ -9,6 +9,7 @@
#include <linux/mm.h>
#include <linux/wait.h>
#include <linux/hash.h>
+#include <linux/kthread.h>
void __init_waitqueue_head(wait_queue_head_t *q, const char *name, struct lock_class_key *key)
{
@@ -297,6 +298,10 @@ int autoremove_wake_function(wait_queue_t *wait, unsigned mode, int sync, void *
}
EXPORT_SYMBOL(autoremove_wake_function);
+static inline bool is_kthread_should_stop(void)
+{
+ return (current->flags & PF_KTHREAD) && kthread_should_stop();
+}
/*
* DEFINE_WAIT_FUNC(wait, woken_wake_func);
@@ -326,7 +331,7 @@ long wait_woken(wait_queue_t *wait, unsigned mode, long timeout)
* woken_wake_function() such that if we observe WQ_FLAG_WOKEN we must
* also observe all state before the wakeup.
*/
- if (!(wait->flags & WQ_FLAG_WOKEN))
+ if (!(wait->flags & WQ_FLAG_WOKEN) && !is_kthread_should_stop())
timeout = schedule_timeout(timeout);
__set_current_state(TASK_RUNNING);