From: Paolo Bonzini <pbonzini@redhat.com>
To: Fam Zheng <famz@redhat.com>, qemu-devel@nongnu.org
Cc: Jason Wang <jasowang@redhat.com>,
qemu-stable@nongnu.org, "Michael S. Tsirkin" <mst@redhat.com>
Subject: Re: [Qemu-devel] [PATCH v2] virtio: Move memory_listener_unregister to .unrealize
Date: Tue, 16 May 2017 11:23:06 +0200 [thread overview]
Message-ID: <e780d3d8-43f1-f46d-2858-7554a334246b@redhat.com> (raw)
In-Reply-To: <20170516080737.GB27669@lemon.lan>
On 16/05/2017 10:07, Fam Zheng wrote:
> On Tue, 05/16 15:24, Fam Zheng wrote:
>> The root cause of the crash is not obvious here, but the change
>> regardlessly makes sense so it's proposed here: the listener was
>> registered in .realize(), so do the cleanup in the matching .unrealize()
>> rather than the .finalize() callback.
This is not entirely true.
Unrealize is the point where the device doesn't get any more requests.
Instance finalize is the point where there are no references anymore.
If a pending request has a reference to X, instance finalize is the
right place to free X.
However, in this case using .unrealize() should be fine.
> Actually it seem calling memory_listener_unregister in .instance_finalize is not
> safe because it can be in the RCU thread. This race is what caused the
> corruption of the listener lists.
RCU callbacks are called with BQL held, so that shouldn't be it. But
the patch should be okay anyway.
Paolo
next prev parent reply other threads:[~2017-05-16 9:23 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-05-16 7:24 [Qemu-devel] [PATCH v2] virtio: Move memory_listener_unregister to .unrealize Fam Zheng
2017-05-16 8:07 ` Fam Zheng
2017-05-16 9:23 ` Paolo Bonzini [this message]
2017-05-16 12:25 ` Fam Zheng
2017-05-16 12:44 ` Paolo Bonzini
2017-05-17 1:55 ` Fam Zheng
2017-05-17 6:58 ` Paolo Bonzini
2017-05-17 12:00 ` Fam Zheng
2017-05-17 12:52 ` Paolo Bonzini
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