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Date: Sun, 24 Oct 2010 09:00:49 +0200 From: Jens Axboe <jaxboe@...ionio.com> To: Vivek Goyal <vgoyal@...hat.com> CC: Eric Dumazet <eric.dumazet@...il.com>, Yasuaki Ishimatsu <isimatu.yasuaki@...fujitsu.com>, linux-kernel <linux-kernel@...r.kernel.org> Subject: Re: [BUG] disk_free_ptbl_rcu_cb() crash On 2010-10-24 08:52, Vivek Goyal wrote: > On Sun, Oct 24, 2010 at 08:04:31AM +0200, Jens Axboe wrote: >> On 2010-10-23 23:10, Eric Dumazet wrote: >>> Current Linus tree makes my machine crash in disk_free_ptbl_rcu_cb(), >>> while booting... >>> >>> commit 7681bfeeccff5ef seems the problem ? >>> >>> Following patch solves the NULL dereference, but this is only to show >>> you where the problem is, not a real fix, of course. >> >> Darn. Your fix is on the right path, you missed one though. I think it's >> cleaner to move this into the elevator helpers, so that the callers can >> remain clean. >> >> Can you verify that this works too? > > Hi Jens, > > I am wondering if this fix is safe. Looking at the memstick backtrace in > other mail thread, it looks like request queue itself has been freed. So we > probably should be checking for request queue being valid before we try to > check q->elevator being valid. Looking at that trace, it's not yet deleted. But if it's in the to-free path, by the time we invoke the rcu callback and do the quiesce end it could be gone. Needs a bit of thought, feel free to poke at it today if you have time (because I really do not :-/) I will ask Linus to revert this commit for now. > P.S. I tried sending the same response from gmail account but it bounced. > So if you get this mail twice, please ignore. Didn't get it twice. -- Jens Axboe -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.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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