linux-kernel - Re: [PATCH] signal: annotate siglock acquisition

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Date:	Sat, 25 Sep 2010 14:23:43 +0200
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Namhyung Kim <namhyung@...il.com>
Cc:	Oleg Nesterov <oleg@...hat.com>,
	Roland McGrath <roland@...hat.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] signal: annotate siglock acquisition

Le samedi 25 septembre 2010 à 20:33 +0900, Namhyung Kim a écrit :

> What's the difference? I didn't change the semantics of likely clause
> but simply exchange the order of then-else part because IMHO a
> negative expression make it hard to understand, generally.
> I've checked compiled binaries for both cases on x86 and they
> produced exactly same code.
> 


Anyway, re-reading your patch, I just dont get why you use __cond_lock()
two times, but not on this part ?

if (!likely(__cond_lock(&t->sighand->siglock,
			lock_task_sighand(t, &flags))))
	goto ret;

This way, your patch would not be misleading.


Another way to deal with this sparse mess is to use a macro, like we do
for read_trylock() :

#define read_trylock(lock)    __cond_lock(lock, _raw_read_trylock(lock))

-->

#define lock_task_sighand(t, flags) 			\
	__cond_lock(&(t)->sighand->siglock,		\
		    _raw_lock_task_sighand(t, flags))



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