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Re: Is gcc thread-unsafe?

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From: Linus Torvalds <torvalds@...>
To: Andi Kleen <ak@...>
Cc: Nick Piggin <nickpiggin@...>, Linux Kernel Mailing List <linux-kernel@...>
Subject: Re: Is gcc thread-unsafe?
Date: Thursday, October 25, 2007 - 7:32 pm

On Fri, 26 Oct 2007, Andi Kleen wrote:

I "conveniently snipped it" because it was pointless.

"adc" or "cmov" has nothing what-so-ever to do with it. If some routine 
returns 0-vs-1 and gcc then turns "if (routine()) x++" into 
"x+=routine()", what does that have to do with adc or cmov?

The fact is, these kinds of optimizations are *bogus* and they are 
dangerous.

Now, it's equally true that we probably don't have those kinds of patterns 
in the kernel, and we'll probabaly not hit it, but wouldn't it be much 
better to make sure that compilers shouldn't do that?

			Linus
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Messages in current thread:
Is gcc thread-unsafe?, Nick Piggin, (Wed Oct 24, 11:24 pm)
Re: Is gcc thread-unsafe?, Phillip Susi, (Wed Oct 31, 6:10 pm)
Re: Is gcc thread-unsafe?, Linus Torvalds, (Thu Oct 25, 10:55 am)
Re: Is gcc thread-unsafe?, Ismail , (Thu Oct 25, 6:26 pm)
Re: Is gcc thread-unsafe?, Jeff Garzik, (Thu Oct 25, 6:56 pm)
Re: Is gcc thread-unsafe?, Jeff Garzik, (Thu Oct 25, 7:04 pm)
RE: Is gcc thread-unsafe?, David Schwartz, (Thu Oct 25, 5:42 pm)
Re: Is gcc thread-unsafe?, Nick Piggin, (Thu Oct 25, 7:22 pm)
Re: Is gcc thread-unsafe?, Andrew Haley, (Fri Oct 26, 7:59 am)
Re: Is gcc thread-unsafe?, Andrew Haley, (Fri Oct 26, 7:59 am)
Re: Is gcc thread-unsafe?, Chris Friesen, (Fri Oct 26, 1:39 pm)
Re: Is gcc thread-unsafe?, Pekka Enberg, (Thu Oct 25, 11:12 am)
Re: Is gcc thread-unsafe?, Andi Kleen, (Thu Oct 25, 3:15 am)
Re: Is gcc thread-unsafe?, Nick Piggin, (Thu Oct 25, 6:49 pm)
Re: Is gcc thread-unsafe?, Andi Kleen, (Thu Oct 25, 7:09 pm)
Re: Is gcc thread-unsafe?, Nick Piggin, (Thu Oct 25, 7:43 pm)
Re: Is gcc thread-unsafe?, Andi Kleen, (Thu Oct 25, 7:55 pm)
Re: Is gcc thread-unsafe?, Nick Piggin, (Thu Oct 25, 7:57 pm)
Re: Is gcc thread-unsafe?, Linus Torvalds, (Thu Oct 25, 7:14 pm)
Re: Is gcc thread-unsafe?, Andi Kleen, (Thu Oct 25, 7:16 pm)
Re: Is gcc thread-unsafe?, Linus Torvalds, (Thu Oct 25, 7:32 pm)
Re: Is gcc thread-unsafe?, Andi Kleen, (Thu Oct 25, 7:42 pm)
Re: Is gcc thread-unsafe?, Willy Tarreau, (Fri Oct 26, 12:57 am)
Re: Is gcc thread-unsafe?, Linus Torvalds, (Thu Oct 25, 7:57 pm)
Re: Is gcc thread-unsafe?, Zachary Amsden, (Thu Oct 25, 9:15 pm)
Re: Is gcc thread-unsafe?, linux-os (Dick Johnson), (Thu Oct 25, 7:58 am)
Re: Is gcc thread-unsafe?, Andi Kleen, (Thu Oct 25, 8:16 am)
Re: Is gcc thread-unsafe?, Arjan van de Ven, (Wed Oct 24, 11:46 pm)
Re: Is gcc thread-unsafe?, Nick Piggin, (Wed Oct 24, 11:58 pm)
RE: Is gcc thread-unsafe?, David Schwartz, (Thu Oct 25, 12:29 am)
Re: Is gcc thread-unsafe?, Nick Piggin, (Thu Oct 25, 12:47 am)
Re: Is gcc thread-unsafe?, Samuel Tardieu, (Thu Oct 25, 5:44 am)
Re: Is gcc thread-unsafe?, Andi Kleen, (Thu Oct 25, 5:55 am)
Re: Is gcc thread-unsafe?, Arjan van de Ven, (Thu Oct 25, 12:35 am)