Messages in this thread Patch in this message | | | From | David Howells <> | Subject | [PATCH] Fix coredump vs exec deadlock | Date | Tue, 25 Apr 2006 20:49:41 +0100 |
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Fix a race between the coredump code and the exec dethreader that causes the two to deadlock.
The problem is that if both events happen simultaneously (exec and death by signal) in two different threads, both threads sit there waiting for the other to die.
This patch makes exec inferior to death by signal, the dethreader for the former aborting if it detects the latter.
I've also fixed a potential race in which de_thread() was doing a wait loop, but with the setting of the task state _after_ the loop condition check. I've moved the task state set before the check.
Signed-Off-By: David Howells <dhowells@redhat.com> --- warthog>diffstat -p1 /tmp/dethread.diff fs/exec.c | 16 ++++++++++++++-- 1 file changed, 14 insertions(+), 2 deletions(-)
diff --git a/fs/exec.c b/fs/exec.c index 3a79d97..b66cc82 100644 --- a/fs/exec.c +++ b/fs/exec.c @@ -647,10 +647,13 @@ static int de_thread(struct task_struct hrtimer_restart(&sig->real_timer); spin_lock_irq(lock); } - while (atomic_read(&sig->count) > count) { + for (;;) { + set_current_state(TASK_UNINTERRUPTIBLE); + if (atomic_read(&sig->count) <= count || + tsk->mm->core_startup_done) + break; sig->group_exit_task = current; sig->notify_count = count; - __set_current_state(TASK_UNINTERRUPTIBLE); spin_unlock_irq(lock); schedule(); spin_lock_irq(lock); @@ -658,6 +661,13 @@ static int de_thread(struct task_struct sig->group_exit_task = NULL; sig->notify_count = 0; spin_unlock_irq(lock); + __set_current_state(TASK_RUNNING); + + /* exec loses out to death-by-signal in some other thread */ + if (tsk->mm->core_startup_done) { + kmem_cache_free(sighand_cachep, newsighand); + return -EINTR; + } /* * At this point all other threads have exited, all we have to @@ -1394,6 +1404,8 @@ static void zap_threads (struct mm_struc do_each_thread(g,p) if (mm == p->mm && p != tsk) { force_sig_specific(SIGKILL, p); + /* make sure de_thread() gets the message */ + wake_up_state(p, TASK_UNINTERRUPTIBLE); mm->core_waiters++; if (unlikely(p->ptrace) && unlikely(p->parent->mm == mm)) - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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