diff options
| author | Oleg Nesterov <oleg@redhat.com> | 2009-08-24 12:45:29 +0200 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@suse.de> | 2009-09-08 20:17:39 -0700 |
| commit | 3b9246e2b55f8aa3c3d9732d0eb7e9943a6f9492 (patch) | |
| tree | 0dffe0a70c041e77d16fe13599236bc2919f68d2 | |
| parent | 54cbd776461dabc08ee378249c93185b1f4a33e1 (diff) | |
kthreads: fix kthread_create() vs kthread_stop() race
The bug should be "accidently" fixed by recent changes in 2.6.31,
all kernels <= 2.6.30 need the fix. The problem was never noticed before,
it was found because it causes mysterious failures with GFS mount/umount.
Credits to Robert Peterson. He blaimed kthread.c from the very beginning.
But, despite my promise, I forgot to inspect the old implementation until
he did a lot of testing and reminded me. This led to huge delay in fixing
this bug.
kthread_stop() does put_task_struct(k) before it clears kthread_stop_info.k.
This means another kthread_create() can re-use this task_struct, but the
new kthread can still see kthread_should_stop() == T and exit even without
calling threadfn().
Reported-by: Robert Peterson <rpeterso@redhat.com>
Tested-by: Robert Peterson <rpeterso@redhat.com>
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
| -rw-r--r-- | kernel/kthread.c | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/kernel/kthread.c b/kernel/kthread.c index 96cff2f8710..9548d5210d2 100644 --- a/kernel/kthread.c +++ b/kernel/kthread.c @@ -213,12 +213,12 @@ int kthread_stop(struct task_struct *k) /* Now set kthread_should_stop() to true, and wake it up. */ kthread_stop_info.k = k; wake_up_process(k); - put_task_struct(k); /* Once it dies, reset stop ptr, gather result and we're done. */ wait_for_completion(&kthread_stop_info.done); kthread_stop_info.k = NULL; ret = kthread_stop_info.err; + put_task_struct(k); mutex_unlock(&kthread_stop_lock); return ret; |