On Wed, Oct 09, 2013 at 05:18:53PM +0200, Jan Kara wrote:
> This is really weird. We are delivering a signal to a task. While task is
ITYM "a fatal signal"
> returning from kernel space we are running queued task works and one of
get_signal_to_deliver() notices that the signal has to be dealt with
via default reaction, which happens to be "die, you bastard". So it
calls do_group_exit(). Which means that we'll never be returning to userland,
so the time to run pending __fput() is now.
> that works is dropping last file reference. Ext4 then does some data
> flushing and at that point we find out irqs are disabled. It isn't really
> clear to me where in that call chain got irqs disabled. I went through it
> and didn't find any such place... If this is reproducible, there would be
> ways to debug this (like irq tracing). Otherwise I'm not sure... I'm CCing
> Al since he was digging in this code recently. Maybe he will have some
> idea.
Note that do_group_exit() is preceded by
spin_unlock_irq(&sighand->siglock);
so no matter what happened in callers, irq is enabled. I'd suggest sticking
such BUG_ON() into __fput() and trying to reproduce that crap...
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