Messages in this thread | | | Subject | Re: v2.6.31-rc6: BUG: unable to handle kernel NULL pointer dereference at 0000000000000008 | From | (Eric W. Biederman) | Date | Mon, 24 Aug 2009 18:41:15 -0700 |
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Linus Torvalds <torvalds@linux-foundation.org> writes:
> On Mon, 24 Aug 2009, Linus Torvalds wrote: >> >> But I wanted to let people know that the patch is clearly not the "last >> word" on this. It's a useful thing to try, but we need something better. > > This may be better (this is a replacement for the previous patch). > > Instead of using 'cancel_delayed_work_sync()', it makes tty_ldisc_hangup() > do a 'flush_scheduled_work()' afterwards, like the other callers already > do. > > And like 'tty_ldisc_release()' already does, it does this all before even > getting the ldisc_mutex, avoiding the deadlock. > > I'm not 100% happy with this patch either, but my remaining unhappiness is > more with the tty locking in general that causes this all. I suspect this > patch in itself is not any worse than the other hacks we have. > > Oh, and in case you didn't guess - this is _STILL_ totally untested. It > compiles for me, but that's all I'm going to guarantee. I'm just looking > at the code (and getting pretty fed up with it ;) > > And as already mentioned: I doubt the deadlock on tty->ldisc_mutex is > anything that would be hit in practice. And even if it can be triggered, > the previous patch I sent out is still interesting in a "does it make the > problem go away" sense. Because if it doesn't (with or without a new > deadlock), then I'm looking at all the wrong places.
Assuming no one beats me to it I should be able to test this tomorrow.
Eric
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