linux-kernel - Re: [patch] IA64: suppress return value of down_trylock() in salinfo_work_to

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Message-ID: <20080803013159.GB26461@parisc-linux.org>
Date:	Sat, 2 Aug 2008 19:32:00 -0600
From:	Matthew Wilcox <matthew@....cx>
To:	Simon Horman <horms@...ge.net.au>
Cc:	linux-ia64@...r.kernel.org, linux-kernel@...r.kernel.org,
	Tony Luck <tony.luck@...el.com>, Keith Owens <kaos@....com.au>
Subject: Re: [patch] IA64: suppress return value of down_trylock() in salinfo_work_to_do()

On Sun, Aug 03, 2008 at 10:06:58AM +1000, Simon Horman wrote:
> salinfo_work_to_do() intentionally ignores the return value of
> down_trylock() and calls up() regardless of if the lock
> was taken or not.
> 
> This patch suppresses the warning generated by ignoring
> this return value - down_trylock() is annotated with __must_check.

I can't say that I think this is a good idea.  Has anyone looked at what
it would take to actually track this?  For example, could we ever have
the situation where:

task A acquires sem

task B tries to acquire the sem, fails
task B releases the sem that it didn't acquire

task A releases the sem, falls down, goes boom?

(of course, this is a semaphores, not a mutex, so it'll now be a
counting semaphore with n=2, not protecting a damn thing).

-- 
Intel are signing my paycheques ... these opinions are still mine
"Bill, look, we understand that you're interested in selling us this
operating system, but compare it to ours.  We can't possibly take such
a retrograde step."
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