From: "Alex Bennée" <alex.bennee@linaro.org>
To: Peter Maydell <peter.maydell@linaro.org>
Cc: Paolo Bonzini <pbonzini@redhat.com>,
QEMU Developers <qemu-devel@nongnu.org>
Subject: Re: [PATCH] qemu/atomic.h: add #ifdef guards for stdatomic.h
Date: Thu, 26 Mar 2020 17:32:08 +0000 [thread overview]
Message-ID: <87a743nht3.fsf@linaro.org> (raw)
In-Reply-To: <CAFEAcA8Lo84gNk2tFCKsgM_O50bXTCs6Z9jH6aCvfDA56TDCmA@mail.gmail.com>
Peter Maydell <peter.maydell@linaro.org> writes:
> On Thu, 26 Mar 2020 at 17:01, Alex Bennée <alex.bennee@linaro.org> wrote:
>>
>> Deep inside the FreeBSD netmap headers we end up including stdatomic.h
>> which clashes with qemu's atomic functions which are modelled along
>> the C11 standard. To avoid a massive rename lets just ifdef around the
>> problem.
>>
>> Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
>> ---
>> include/qemu/atomic.h | 6 ++++++
>> 1 file changed, 6 insertions(+)
>>
>> diff --git a/include/qemu/atomic.h b/include/qemu/atomic.h
>> index f9cd24c8994..ff72db51154 100644
>> --- a/include/qemu/atomic.h
>> +++ b/include/qemu/atomic.h
>> @@ -208,11 +208,14 @@
>> /* Provide shorter names for GCC atomic builtins, return old value */
>> #define atomic_fetch_inc(ptr) __atomic_fetch_add(ptr, 1, __ATOMIC_SEQ_CST)
>> #define atomic_fetch_dec(ptr) __atomic_fetch_sub(ptr, 1, __ATOMIC_SEQ_CST)
>> +
>> +#ifndef atomic_fetch_add
>> #define atomic_fetch_add(ptr, n) __atomic_fetch_add(ptr, n, __ATOMIC_SEQ_CST)
>> #define atomic_fetch_sub(ptr, n) __atomic_fetch_sub(ptr, n, __ATOMIC_SEQ_CST)
>> #define atomic_fetch_and(ptr, n) __atomic_fetch_and(ptr, n, __ATOMIC_SEQ_CST)
>> #define atomic_fetch_or(ptr, n) __atomic_fetch_or(ptr, n, __ATOMIC_SEQ_CST)
>> #define atomic_fetch_xor(ptr, n) __atomic_fetch_xor(ptr, n, __ATOMIC_SEQ_CST)
>> +#endif
>
> This will work around FreeBSD's current implementation in particular,
> but I don't think there's anything in the C11 spec that mandates that
> atomic_fetch_add() and friends have to be macros and not simply
> functions...
Sure there are two alternative options:
- Move to using stdatomic headers - on Linux they seem to be C++ only
- Rename all out atomic functions - seems a bit of a big patch for rc releases
I suspect we should look at option two for 5.1
--
Alex Bennée
next prev parent reply other threads:[~2020-03-26 17:32 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-03-26 17:01 [PATCH] qemu/atomic.h: add #ifdef guards for stdatomic.h Alex Bennée
2020-03-26 17:14 ` Peter Maydell
2020-03-26 17:32 ` Alex Bennée [this message]
2020-03-26 18:05 ` Paolo Bonzini
2020-03-26 20:19 ` Peter Maydell
2020-03-27 9:51 ` Alex Bennée
2020-03-27 13:35 ` Richard Henderson
2020-03-26 19:58 ` Richard Henderson
2020-03-26 20:05 ` Paolo Bonzini
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