From: Paolo Bonzini <pbonzini@redhat.com>
To: Sasha Levin <levinsasha928@gmail.com>
Cc: aliguori@us.ibm.com, aik@ozlabs.ru, rusty@rustcorp.com.au,
agraf@suse.de, qemu-devel@nongnu.org,
David Gibson <david@gibson.dropbear.id.au>
Subject: Re: [Qemu-devel] [PATCH] virtio: Make memory barriers be memory barriers
Date: Thu, 01 Sep 2011 09:56:25 +0200 [thread overview]
Message-ID: <4E5F3AA9.5020804@redhat.com> (raw)
In-Reply-To: <1314862622.26813.6.camel@lappy>
On 09/01/2011 09:37 AM, Sasha Levin wrote:
>> > -#define wmb() __asm__ __volatile__("": : :"memory")
>> > + /* TODO: we may also need rmb()s. It hasn't bitten us yet, but.. */
>> > + #define wmb() __sync_synchronize()
>
> That asm directive also implicitly provided a compiler barrier, I could
^^^^
only
> find whether __sync_synchronize() provides one as well.
>
> Any idea if it does?
Of course, __sync_synchronize() is a stronger barrier. The asm is
simply not a synchronization primitive.
Paolo
next prev parent reply other threads:[~2011-09-01 7:56 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-09-01 6:09 [Qemu-devel] [PATCH] virtio: Make memory barriers be memory barriers David Gibson
2011-09-01 6:47 ` Paolo Bonzini
2011-09-02 0:08 ` David Gibson
2011-09-02 6:49 ` Paolo Bonzini
2011-09-03 11:53 ` Blue Swirl
2011-09-01 7:37 ` Sasha Levin
2011-09-01 7:38 ` Sasha Levin
2011-09-01 7:56 ` Paolo Bonzini [this message]
2011-09-02 0:09 ` David Gibson
2011-09-01 15:30 ` Michael S. Tsirkin
2011-09-01 16:14 ` Paolo Bonzini
2011-09-01 16:34 ` Michael S. Tsirkin
2011-09-01 20:31 ` Paolo Bonzini
2011-09-02 15:45 ` Michael S. Tsirkin
2011-09-03 14:46 ` David Gibson
2011-09-04 9:16 ` Michael S. Tsirkin
2011-09-05 4:43 ` David Gibson
2011-09-05 9:19 ` Michael S. Tsirkin
2011-09-06 3:12 ` David Gibson
2011-09-06 6:55 ` Paolo Bonzini
2011-09-06 9:02 ` David Gibson
2011-09-06 9:28 ` Avi Kivity
2011-09-06 9:35 ` Michael S. Tsirkin
2011-09-06 9:38 ` Paolo Bonzini
2011-09-05 7:41 ` Paolo Bonzini
2011-09-05 8:06 ` Michael S. Tsirkin
2011-09-05 9:42 ` Paolo Bonzini
2011-09-03 16:19 ` Paolo Bonzini
2011-09-04 8:47 ` Michael S. Tsirkin
2011-09-02 0:11 ` David Gibson
2011-09-02 6:11 ` Paolo Bonzini
2011-09-02 15:57 ` Michael S. Tsirkin
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