From: Kevin Wolf <kwolf@redhat.com>
To: Christoph Hellwig <hch@lst.de>
Cc: Peter Lieven <pl@dlh.net>, qemu-devel@nongnu.org, kvm@vger.kernel.org
Subject: Re: qemu-kvm hangs if multipath device is queing
Date: Wed, 19 May 2010 09:48:47 +0200 [thread overview]
Message-ID: <4BF397DF.2030108@redhat.com> (raw)
In-Reply-To: <20100519072902.GA711@lst.de>
Am 19.05.2010 09:29, schrieb Christoph Hellwig:
> On Tue, May 18, 2010 at 03:22:36PM +0200, Kevin Wolf wrote:
>> I think it's stuck here in an endless loop:
>>
>> while (laiocb->ret == -EINPROGRESS)
>> qemu_laio_completion_cb(laiocb->ctx);
>>
>> Can you verify this by single-stepping one or two loop iterations? ret
>> and errno after the read call could be interesting, too.
>
> Maybe the compiler is just too smart. Without some form of barrier
> it could just optimize the loop away as laiocb->ret couldn't change
> in a normal single-threaded environment.
It probably could in theory, but in practice we're in a read() inside
qemu_laio_completion, so it didn't do it here.
Kevin
WARNING: multiple messages have this Message-ID (diff)
From: Kevin Wolf <kwolf@redhat.com>
To: Christoph Hellwig <hch@lst.de>
Cc: Peter Lieven <pl@dlh.net>, qemu-devel@nongnu.org, kvm@vger.kernel.org
Subject: [Qemu-devel] Re: qemu-kvm hangs if multipath device is queing
Date: Wed, 19 May 2010 09:48:47 +0200 [thread overview]
Message-ID: <4BF397DF.2030108@redhat.com> (raw)
In-Reply-To: <20100519072902.GA711@lst.de>
Am 19.05.2010 09:29, schrieb Christoph Hellwig:
> On Tue, May 18, 2010 at 03:22:36PM +0200, Kevin Wolf wrote:
>> I think it's stuck here in an endless loop:
>>
>> while (laiocb->ret == -EINPROGRESS)
>> qemu_laio_completion_cb(laiocb->ctx);
>>
>> Can you verify this by single-stepping one or two loop iterations? ret
>> and errno after the read call could be interesting, too.
>
> Maybe the compiler is just too smart. Without some form of barrier
> it could just optimize the loop away as laiocb->ret couldn't change
> in a normal single-threaded environment.
It probably could in theory, but in practice we're in a read() inside
qemu_laio_completion, so it didn't do it here.
Kevin
next prev parent reply other threads:[~2010-05-19 7:49 UTC|newest]
Thread overview: 34+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-05-03 21:26 Qemu-KVM 0.12.3 and Multipath -> Assertion Peter Lieven
2010-05-03 21:26 ` [Qemu-devel] " Peter Lieven
2010-05-04 5:38 ` André Weidemann
2010-05-04 5:38 ` [Qemu-devel] " André Weidemann
2010-05-04 8:35 ` [Qemu-devel] " Kevin Wolf
2010-05-04 8:35 ` Kevin Wolf
2010-05-04 11:38 ` Peter Lieven
2010-05-04 11:38 ` Peter Lieven
2010-05-04 12:20 ` Kevin Wolf
2010-05-04 12:20 ` Kevin Wolf
2010-05-04 13:42 ` Peter Lieven
2010-05-04 13:42 ` Peter Lieven
2010-05-04 14:01 ` Kevin Wolf
2010-05-04 14:01 ` Kevin Wolf
2010-05-04 17:07 ` Christoph Hellwig
2010-05-18 11:13 ` Peter Lieven
2010-05-18 12:14 ` Kevin Wolf
2010-05-18 12:14 ` Kevin Wolf
2010-05-12 14:01 ` qemu-kvm hangs if multipath device is queing (was: Re: [Qemu-devel] Qemu-KVM 0.12.3 and Multipath -> Assertion) Peter Lieven
2010-05-14 9:26 ` qemu-kvm hangs if multipath device is queing Kevin Wolf
2010-05-14 9:26 ` [Qemu-devel] " Kevin Wolf
2010-05-18 11:10 ` Peter Lieven
2010-05-18 11:10 ` [Qemu-devel] " Peter Lieven
2010-05-18 13:22 ` Kevin Wolf
2010-05-18 13:22 ` [Qemu-devel] " Kevin Wolf
2010-05-19 7:29 ` Christoph Hellwig
2010-05-19 7:29 ` [Qemu-devel] " Christoph Hellwig
2010-05-19 7:48 ` Kevin Wolf [this message]
2010-05-19 7:48 ` Kevin Wolf
2010-05-19 8:18 ` Peter Lieven
2010-05-19 8:18 ` [Qemu-devel] " Peter Lieven
2010-05-23 10:30 ` Peter Lieven
2010-05-08 9:53 ` [Qemu-devel] Qemu-KVM 0.12.3 and Multipath -> Assertion André Weidemann
2010-05-08 9:53 ` André Weidemann
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