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Message-ID: <CA+1xoqf0d5ckDZ3o1-Y+qd61nvVA7EECeH20U+WjDpNVb4E=pw@mail.gmail.com> Date: Wed, 26 Dec 2012 13:09:51 -0500 From: Sasha Levin <levinsasha928@...il.com> To: Cong Wang <xiyou.wangcong@...il.com> Cc: Josh Boyer <jwboyer@...il.com>, Alan Cox <alan@...rguk.ukuu.org.uk>, LKML <linux-kernel@...r.kernel.org>, Florian Tobias Schandinat <florianSchandinat@....de>, Linus Torvalds <torvalds@...ux-foundation.org> Subject: Re: [PATCH] fb: Rework locking to fix lock ordering on takeover On Tue, Dec 25, 2012 at 9:41 PM, Cong Wang <xiyou.wangcong@...il.com> wrote: > On Wed, Dec 26, 2012 at 12:08 AM, Sasha Levin <levinsasha928@...il.com> wrote: >> On Tue, Dec 18, 2012 at 10:20 AM, Josh Boyer <jwboyer@...il.com> wrote: >>> On Wed, Nov 21, 2012 at 7:53 AM, Alan Cox <alan@...rguk.ukuu.org.uk> wrote: >>>> On Wed, 21 Nov 2012 07:45:45 -0500 >>>> Josh Boyer <jwboyer@...il.com> wrote: >>>> >>>>> On Fri, Nov 16, 2012 at 2:27 PM, Alan Cox <alan@...rguk.ukuu.org.uk> wrote: >>>>> > >>>>> > [The fb maintainer appears to be absent at the moment]. >>>>> > >>>>> > This is needed to fix a pile of lockdep splats that now show up because console_lock() >>>>> > is being properly audited. Hugh Dickins and Sasha Levin have tested it and both reports >>>>> > all looks good. This is probably not the whole story - the entire fb layer has locking >>>>> > confusion problems that were previously hidden but it seems to get the ones people hit >>>>> > in testing. This hopefully explains a few of the weird fb hangs that have been floating >>>>> > around forever. >>>>> > >>>>> > From: Alan Cox <alan@...ux.intel.com> >>>>> > >>>>> > Adjust the console layer to allow a take over call where the caller already >>>>> > holds the locks. Make the fb layer lock in order. >>>>> > >>>>> > This s partly a band aid, the fb layer is terminally confused about the >>>>> > locking rules it uses for its notifiers it seems. >>>>> > >>>>> > Signed-off-by: Alan Cox <alan@...ux.intel.com> >>>>> >>>>> Should this eventually get into the stable trees? >>>> >>>> Thats a question I'm not sure about at this point. I think the bug is >>>> real but not caught by the lock checker in older trees but I've not >>>> investigated. >>> >>> So... this patch seems to still be twisting in the wind. It should >>> probably be headed into 3.8 at this point, shouldn't it? >> >> Indeed it should. I'm seeing the original warnings in 3.8-rc1 and have >> to carry this patch to avoid them. > > This patch can fix the following warning we saw? > http://lkml.org/lkml/2012/12/22/53 > > I will give it a try. Yup, that's the same error I've reported couple of months ago. It looks like the fb maintains are still absent, so it'll probably need a different way to get upstream. Thanks, Sasha -- 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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