linux-kernel - Re: tasks getting stuck on mmap

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Message-Id: <20100817.164013.193700583.davem@davemloft.net>
Date:	Tue, 17 Aug 2010 16:40:13 -0700 (PDT)
From:	David Miller <davem@...emloft.net>
To:	torvalds@...ux-foundation.org
Cc:	tony.luck@...el.com, walken@...gle.com, dhowells@...hat.com,
	akpm@...ux-foundation.org, linux-kernel@...r.kernel.org
Subject: Re: tasks getting stuck on mmap_sem?

From: Linus Torvalds <torvalds@...ux-foundation.org>
Date: Tue, 17 Aug 2010 14:28:49 -0700

> Oh, and it strikes me when looking at the sparc rwsem-const.h that it
> has some unsigned constants in it. I think
> 
>   #define RWSEM_WAITING_BIAS              0xffff0000
> 
> is actually unsigned, because it's a hex constant that doesn't fit in
> a signed int. So it's of type 'unsigned int' if I recall the C type
> rules right.

You were right all along, of course.  Nice spotting.

Something was messed up with my testing methodology last night such
that I didn't test the revert of the lib/rwsem.c changes properly.
Those actually did in fact introduce the problem.

And fixing these sparc rwsem values to be signed constants fixes the bug.

Thanks guys.
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