linux-kernel - Re: [2.6.27-rc5] inotify_read's ev_mutex vs do_page_fault's mmap

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Message-Id: <200809101950.27669.nickpiggin@yahoo.com.au>
Date:	Wed, 10 Sep 2008 19:50:27 +1000
From:	Nick Piggin <nickpiggin@...oo.com.au>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Daniel J Blueman <daniel.blueman@...il.com>,
	torvalds@...ux-foundation.org,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linux Kernel <linux-kernel@...r.kernel.org>
Subject: Re: [2.6.27-rc5] inotify_read's ev_mutex vs do_page_fault's mmap_sem...

On Wednesday 10 September 2008 18:37, Ingo Molnar wrote:
> * Nick Piggin <nickpiggin@...oo.com.au> wrote:
> > On Wednesday 10 September 2008 17:57, Peter Zijlstra wrote:

> > > Sure, how about the below - untested - uncompiled, might eat kittens,
> > > etc..
> > >
> > > Just sprinkle something like:
> > >
> > >   might_lock_read(&mm->mmap_sem);
> > >
> > > in the right places.
> >
> > Ahh, very nice, thanks! I'll give that a try...
>
> cool! Please send in an RFC patch once you have something that boots -
> we can stick it into tip/core/locking and see whether there's any new
> messages on a wide range of systems and workloads. (and we'd also check
> whether the number of kittens is an invariant.)

Well I have verified it boots, and have used the annotation in some of
x86-64's user copy routines (luckily no flood of bugs I was scared of,
phew!)

So I would like to request you merge Peter's patch, and we'll hopefully
start seeing the annotations being used. FWIW, I don't suppose lockdep
can determine that it is a sleeping lock, and do the appropriate
might_sleep checks at this point as well?

Thanks,
Nick


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