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From: Linus Torvalds <torvalds@linux-foundation.org>
To: Steven Rostedt <rostedt@goodmis.org>
Cc: Ingo Molnar <mingo@elte.hu>, Thomas Gleixner <tglx@linutronix.de>,
	LKML <linux-kernel@vger.kernel.org>,
	David Holmes - Sun Microsystems <David.Holmes@Sun.COM>,
	Andrew Morton <akpm@linux-foundation.org>
Subject: Re: [PATCH] fix for futex_wait signal stack corruption
Date: Tue, 4 Dec 2007 14:43:29 -0800 (PST)	[thread overview]
Message-ID: <alpine.LFD.0.9999.0712041436100.13796@woody.linux-foundation.org> (raw)
In-Reply-To: <20071204213924.GA14915@goodmis.org>



On Tue, 4 Dec 2007, Steven Rostedt wrote:
> 
> Seems that arg3 is not used here and since the timer is 64 bits, we can
> store the bottom 32 bits in arg2 and the top in arg3 (this will work for
> both 32 and 64 bit archs).

Yes. That should work fine.

The restart logic sometimes results in odd calling conventions, and quite 
frankly, we could just change how "restart_block" looks too. There is 
nothing that says that it has to be

	unsigned long arg0, arg1, arg2, arg3

and that particular layout was just picked on a whim. The only issue is:

 - we don't want the restart block to be *too* large, since it's part of 
   the thread info.
 - but we need to have enough room for all the system calls that want to 
   use the restart block, and preferably in a reasonable format.

So far, using "unsigned long" has been good enough, in that it's big 
enough for a pointer and all normal arguments, but if something really 
deeply wants another format or a guaranteed 64-bit word regardless of 
architecture, we could make one or more of the arguments be "u64" instead.

But in this case, since there is already unused argument space, I think 
that doing the "32 high bits + 32 low bits" is probably the best option.

			Linus

  reply	other threads:[~2007-12-04 22:44 UTC|newest]

Thread overview: 15+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2007-12-04 20:57 [PATCH] fix for futex_wait signal stack corruption Steven Rostedt
2007-12-04 21:09 ` Linus Torvalds
2007-12-04 21:39   ` Steven Rostedt
2007-12-04 22:43     ` Linus Torvalds [this message]
2007-12-05  1:23       ` Steven Rostedt
2007-12-05  1:46         ` Linus Torvalds
2007-12-05  3:17           ` [PATCH -v2] " Steven Rostedt
2007-12-05  3:41             ` Linus Torvalds
2007-12-05  3:47               ` Randy Dunlap
2007-12-05  3:53                 ` Steven Rostedt
2007-12-05  5:33               ` David Holmes - Sun Microsystems
2007-12-05  6:06                 ` Linus Torvalds
2007-12-05  6:14                   ` David Holmes - Sun Microsystems
2007-12-05  5:54               ` Thomas Gleixner
2007-12-05 10:31                 ` Ingo Molnar

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