Re: Is gcc thread-unsafe?

!MAILaRCHIVE_VOTE_RePLACE
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To: Nick Piggin <nickpiggin@...>
Cc: Linux Kernel Mailing List <linux-kernel@...>, Linus Torvalds <torvalds@...>, Kleen, Andi <ak@...>
Date: Wednesday, October 31, 2007 - 6:10 pm

>             pushl   %ebp

How is this even an optimization?  It looks SLOWER to me.  The 
conditional read wastes memory bandwidth sometimes, if the condition is 
true, and v isn't already in the cache.  The unconditional write wastes 
memory bandwidth ALL the time, and dirties/flushes caches, in addition 
to not being thread safe.

This SHOULD be using a conditional write instead of a conditional read 
and an unconditional write.


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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)