diff options
| author | Oleg Nesterov <oleg@redhat.com> | 2010-05-26 14:43:17 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2010-05-27 09:12:46 -0700 |
| commit | 4ada856fb0ee62f6fe3aac3de726deac0640d929 (patch) | |
| tree | 8dd3efbc19f6e1f1dac2ff7afdcd9658fb08b814 | |
| parent | ea6d290ca34c4fd91b7348338c0cc7bdeff94a35 (diff) | |
signals: clear signal->tty when the last thread exits
When the last thread exits signal->tty is freed, but the pointer is not
cleared and points to nowhere.
This is OK. Nobody should use signal->tty lockless, and it is no longer
possible to take ->siglock. However this looks wrong even if correct, and
the nice OOPS is better than subtle and hard to find bugs.
Change __exit_signal() to clear signal->tty under ->siglock.
Note: __exit_signal() needs more cleanups. It should not check "sig !=
NULL" to detect the all-dead case and we have the same issues with
signal->stats.
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Cc: Alan Cox <alan@linux.intel.com>
Cc: Ingo Molnar <mingo@elte.hu>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Acked-by: Roland McGrath <roland@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
| -rw-r--r-- | kernel/exit.c | 5 |
1 files changed, 4 insertions, 1 deletions
diff --git a/kernel/exit.c b/kernel/exit.c index 92af5cde9bb..356d91fa095 100644 --- a/kernel/exit.c +++ b/kernel/exit.c @@ -80,6 +80,7 @@ static void __exit_signal(struct task_struct *tsk) { struct signal_struct *sig = tsk->signal; struct sighand_struct *sighand; + struct tty_struct *uninitialized_var(tty); BUG_ON(!sig); BUG_ON(!atomic_read(&sig->count)); @@ -93,6 +94,8 @@ static void __exit_signal(struct task_struct *tsk) posix_cpu_timers_exit(tsk); if (thread_group_leader(tsk)) { posix_cpu_timers_exit_group(tsk); + tty = sig->tty; + sig->tty = NULL; } else { /* * If there is any task waiting for the group exit @@ -147,7 +150,7 @@ static void __exit_signal(struct task_struct *tsk) * see account_group_exec_runtime(). */ task_rq_unlock_wait(tsk); - tty_kref_put(sig->tty); + tty_kref_put(tty); } } |