linux-kernel - Re: [PATCH] WorkStruct: Use direct assignment rather than cmpxchg()

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Date:	Sun, 10 Dec 2006 09:19:36 +1100
From:	Benjamin Herrenschmidt <benh@...nel.crashing.org>
To:	David Howells <dhowells@...hat.com>
Cc:	Linux Kernel list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] WorkStruct: Use direct assignment rather than cmpxchg()

>     The problem is where we end up tangling with test_and_set_bit() emulated
>     using spinlocks, and even then it's not a problem _provided_
>     test_and_set_bit() doesn't attempt to modify the word if the bit was
>     set.

I'm not 100% sure what is the problem there, but beware that bitops
don't provide the same semantics as spinlocks regarding memory ordering.

Ben.


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