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From: Linus Torvalds <torvalds@linux-foundation.org>
To: Andreas Schwab <schwab@linux-m68k.org>
Cc: Ingo Molnar <mingo@elte.hu>, Peter Anvin <hpa@zytor.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: x86-32: clean up rwsem inline asm statements
Date: Tue, 12 Jan 2010 17:26:47 -0800 (PST)	[thread overview]
Message-ID: <alpine.LFD.2.00.1001121725110.17145@localhost.localdomain> (raw)
In-Reply-To: <m2fx6ahly3.fsf@igel.home>



On Wed, 13 Jan 2010, Andreas Schwab wrote:

> Linus Torvalds <torvalds@linux-foundation.org> writes:
> 
> > @@ -249,7 +249,7 @@ static inline int rwsem_atomic_update(int delta, struct rw_semaphore *sem)
> >  {
> >  	int tmp = delta;
> >  
> > -	asm volatile(LOCK_PREFIX "xadd %0,%1"
> > +	asm volatile(LOCK_PREFIX "xadd%z0 %0,%1"
> >  		     : "+r" (tmp), "+m" (sem->count)
> >  		     : : "memory");
> 
> I think %z0 should be %z1 here.

You're right, but Peter made it all a non-issue anyway.

Thanks for noticing, though, since it implies that somebody read the patch 
carefully. It's always a bit scary to change fundamental inline asms, 
especially for something like a locking routine where the core _semantics_ 
are so subtle (and if you get locking wrong, things may still work - you 
just end up with some really odd race conditions).

		Linus

  reply	other threads:[~2010-01-13  1:27 UTC|newest]

Thread overview: 18+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2010-01-13  0:21 Linus Torvalds
2010-01-13  0:45 ` Andreas Schwab
2010-01-13  1:26   ` Linus Torvalds [this message]
2010-01-13  0:48 ` H. Peter Anvin
2010-01-13  0:59   ` Linus Torvalds
2010-01-13  1:24     ` x86: avoid read-cycle on down_read_trylock Linus Torvalds
2010-01-13  1:57       ` x86: clean up rwsem type system Linus Torvalds
2010-01-13  2:16         ` Linus Torvalds
2010-01-14  7:03           ` H. Peter Anvin
2010-01-17  6:05             ` Ingo Molnar
2010-01-17 18:24               ` Linus Torvalds
2010-01-21 17:14                 ` Ingo Molnar
2010-01-13  5:03 ` [tip:x86/asm] x86-32: clean up rwsem inline asm statements tip-bot for Linus Torvalds
2010-01-13 19:58 George Spelvin
2010-01-13 21:04 ` H. Peter Anvin
2010-01-14  0:27   ` George Spelvin
2010-01-14  0:39     ` H. Peter Anvin
2010-01-14  1:05   ` Linus Torvalds

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