linux-kernel - Re: [patch] mm: tiny-shmem fix lor, mmap_sem vs i

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Message-Id: <1221772310.4779.29.camel@calx>
Date:	Thu, 18 Sep 2008 14:11:50 -0700
From:	Matt Mackall <mpm@...enic.com>
To:	Jeremy Fitzhardinge <jeremy@...p.org>
Cc:	Ingo Molnar <mingo@...e.hu>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Nick Piggin <npiggin@...e.de>, a.p.zijlstra@...llo.nl,
	linux-kernel@...r.kernel.org, Hugh Dickins <hugh@...itas.com>,
	Dave Hansen <haveblue@...ibm.com>
Subject: Re: [patch] mm: tiny-shmem fix lor, mmap_sem vs i_mutex


On Thu, 2008-09-18 at 12:29 -0700, Jeremy Fitzhardinge wrote:
> Ingo Molnar wrote:
> > in 7 days that's about 7000 random bootups, 20% of which had TINY_SHMEM 
> > enabled, half 32-bit, half 64-bit x86. It did not blow up in any way 
> > that would have prevented the kernel from building its next random 
> > version from within itself and it did not produce any kernel messages 
> > with various random kernel debug, compile and boot options.
> >   
> 
> Does anything in that workload actually use shared memory?

[adding Dave]

For the record, Hugh tracked down the history of this bug and it went
something like this:

- I forked shmem.c and trimmed it down, keeping the function in question
intact
- Dave Hansen made divergent changes to shmem and tiny-shmem for reasons
that aren't immediately obvious
- Al Viro fixed a resultant dput bug
- Nick fixed a resultant deadlock bug by undoing the divergence

As far as Hugh and I can see, there was no reason for the divergent
change. Really, we should probably re-unify the files to prevent such
further confusion.

-- 
Mathematics is the supreme nostalgia of our time.

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