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Date: Tue, 28 Jul 2015 16:09:38 +0200
From: Jens Gustedt <>
Subject: Re: What's left for 1.1.11 release?


Am Montag, den 27.07.2015, 23:40 -0400 schrieb Rich Felker:
> In principle the a_store issue affects all libc-internal __lock/LOCK
> uses,

so this worries me since I assumed that UNLOCK had release consistency
for the __atomic implementation.

> and stdio locks too, but it's only been observed in malloc.
> Since there don't seem to be any performance-relevant uses of a_store
> that don't actually need the proper barrier, I think we have to just
> put an explicit barrier (lock orl $0,(%esp) or mfence) after the store
> and live with the loss of performance.

How about using a xchg as instruction? This would perhaps "waste" a
register, but that sort of optimization should not be critical in the
vicinity of code that needs memory synchronization, anyhow.


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