On Mon, 2005-08-22 at 20:45 +0400, Oleg Nesterov wrote: > Thomas Gleixner wrote: > Ok, exit_itimers()->itimer_delete() called when the last thread exits > or does exec. > > kernel/posix-timers.c:common_timer_del() calls del_timer_sync(), after > that nobody can access this timer, so we don't need to lock timer->it_lock > at all in this case. No lock - no deadlock.
It still deadlocks: CPU 0 CPU 1 write_lock(&tasklist_lock); __exit_signal() timer expires base->running_timer = timer send_group_sigqueue() read_lock(&tasklist_lock(); exit_itimers() del_timer_sync(timer) waits for ever because waits for ever on tasklist_lock base->running_timer == timer I still think the last patch I sent is still necessary. > But I know nothing about kernel/posix-cpu-timers.c, I doubt it will work > for posix_cpu_timer_del(). I don't have time to study posix-cpu-timers now. > However, I see that __exit_signal() calls posix_cpu_timers_exit_xxx(), so > may be it can work? > > 380 int posix_cpu_timer_del(struct k_itimer *timer) > 381 { > 382 struct task_struct *p = timer->it.cpu.task; > 383 > 384 if (timer->it.cpu.firing) > 385 return TIMER_RETRY; > 386 > 387 if (unlikely(p == NULL)) > 388 return 0; > 389 > 390 if (!list_empty(&timer->it.cpu.entry)) { > 391 read_lock(&tasklist_lock); > > Surely, it should be impossible to happen when process exists, otherwise > it would deadlock immediately, we did write_lock(tasklist). > > Thomas, do you know something about posix-cpu-timers.c? Not much. I look into this tglx - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/