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	<57179DE0.5080701@twiddle.net> <20160420171734.GA1124@flamenco>
From: Richard Henderson <rth@twiddle.net>
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Date: Wed, 20 Apr 2016 10:55:45 -0700
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Subject: Re: [Qemu-devel] [PATCH v3 05/11] qemu-thread: add simple
 test-and-set spinlock
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To: "Emilio G. Cota" <cota@braap.org>
Cc: QEMU Developers <qemu-devel@nongnu.org>, MTTCG Devel <mttcg@greensocs.com>, =?UTF-8?Q?Alex_Benn=c3=a9e?= <alex.bennee@linaro.org>, Paolo Bonzini <pbonzini@redhat.com>, Peter Crosthwaite <crosthwaite.peter@gmail.com>, Peter Maydell <peter.maydell@linaro.org>, Sergey Fedorov <serge.fdrv@gmail.com>

On 04/20/2016 10:17 AM, Emilio G. Cota wrote:
> I've tried to find a GCC intrinsic for test-and-set, and I've only found
> lock_test_and_set, which is what we use for atomic_xchg (except on ppc)
> because it really is an atomic exchange:
>   "This builtin, as described by Intel, is not a traditional test-and-set
>    operation, but rather an atomic exchange operation."
>   https://gcc.gnu.org/onlinedocs/gcc-4.1.2/gcc/Atomic-Builtins.html

Please read the entire documentation, not just the first sentence.


r~