Re: [ANNOUNCE] 3.0.4-rt13

Peter Zijlstra
2011-09-12T09:28:44Z

On Sun, 2011-09-11 at 12:35 +0200, Mike Galbraith wrote:
> (gdb) list *do_sigtimedwait+0x62
> 0xffffffff8104f3e2 is in do_sigtimedwait (kernel/signal.c:2628).
> 2623 * Invert the set of allowed signals to get those we want to block.
> 2624 */
> 2625 sigdelsetmask(&mask, sigmask(SIGKILL) | sigmask(SIGSTOP));
> 2626 signotset(&mask);
> 2627
> 2628 spin_lock_irq(&tsk->sighand->siglock);
> 2629 sig = dequeue_signal(tsk, &mask, info);
> 2630 if (!sig && timeout) {
> 2631 /*
> 2632 * None ready, temporarily unblock those we're interested
> (gdb) list *do_sigtimedwait+0x15f
> 0xffffffff8104f4df is in do_sigtimedwait (kernel/signal.c:2642).
> 2637 tsk->real_blocked = tsk->blocked;
> 2638 sigandsets(&tsk->blocked, &tsk->blocked, &mask);
> 2639 recalc_sigpending();
> 2640 spin_unlock_irq(&tsk->sighand->siglock);
> 2641
> 2642 timeout = schedule_timeout_interruptible(timeout);
> 2643
> 2644 spin_lock_irq(&tsk->sighand->siglock);
> 2645 __set_task_blocked(tsk, &tsk->real_blocked);
> 2646 siginitset(&tsk->real_blocked, 0);
>

Right, so what Thomas says.. Now admittedly I haven't had my morning
juice yet, but staring at that function I can't see why that warning
would trigger at all.

I'm going to try and reproduce, but Thomas is already saying he can't,
so I'm not too confident.

I you can easily trigger this, could you add some trace_printk() to
migrate_disable/enable that prints both counters etc.. so we can see wtf
happens?