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 20:33:58 -0700 |
| commit | df221c536aa18008724e57acc4170e0ba38fb11c (patch) | |
| tree | 4fa8971a2052843cf9e03801e5c5ec37892eb55f | |
| parent | 85fa9e247d081a087bed949983dde603a46114dc (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 4ebaf8519ab..7fbaa09fadd 100644 --- a/kernel/kthread.c +++ b/kernel/kthread.c @@ -216,12 +216,12 @@ 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); trace_sched_kthread_stop_ret(ret); |