From: Fam Zheng <famz@redhat.com>
To: Stefan Hajnoczi <stefanha@gmail.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>,
qemu-block@nongnu.org, qemu-devel@nongnu.org,
Stefan Hajnoczi <stefanha@redhat.com>
Subject: Re: [Qemu-devel] [Qemu-block] [PATCH v2 02/13] block: Introduce bdrv_lock and bdrv_unlock API
Date: Wed, 24 Jun 2015 10:47:47 +0800 [thread overview]
Message-ID: <20150624024747.GC1264@ad.nay.redhat.com> (raw)
In-Reply-To: <20150616160736.GD4958@stefanha-thinkpad.redhat.com>
On Tue, 06/16 17:07, Stefan Hajnoczi wrote:
> On Tue, Jun 02, 2015 at 11:21:51AM +0800, Fam Zheng wrote:
> > +/**
> > + * bdrv_lock:
> > + *
> > + * Begin a temporary exclusive accessing by locking the BDS.
> > + */
> > +void bdrv_lock(BlockDriverState *bs);
> > +
> > +/**
> > + * bdrv_unlock:
> > + *
> > + * End a exclusive accessing.
> > + */
> > +void bdrv_unlock(BlockDriverState *bs);
>
> This documentation is missing important points:
>
> 1. Does AioContext need to be held by the caller? (Yes)
Yes.
>
> 2. Is this about thread safety? (No, it's about exclusive access to a
> BDS *within* the AioContext.)
As it has to quiesce iothreads as well (for now it's even more urgent than
exclusive access within the same AioContext), I'd rather take it as yes.
Paolo, please correct me.
BTW, is there any semantics in here that we can use for multiqueue block layer?
Fam
next prev parent reply other threads:[~2015-06-24 2:47 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-06-02 3:21 [Qemu-devel] [PATCH v2 00/13] block: Protect block jobs with lock / unlock API Fam Zheng
2015-06-02 3:21 ` [Qemu-devel] [PATCH v2 01/13] block: Use bdrv_drain to replace uncessary bdrv_drain_all Fam Zheng
2015-06-16 16:01 ` [Qemu-devel] [Qemu-block] " Stefan Hajnoczi
2015-07-07 11:55 ` Stefan Hajnoczi
2015-06-02 3:21 ` [Qemu-devel] [PATCH v2 02/13] block: Introduce bdrv_lock and bdrv_unlock API Fam Zheng
2015-06-16 16:07 ` [Qemu-devel] [Qemu-block] " Stefan Hajnoczi
2015-06-24 2:47 ` Fam Zheng [this message]
2015-06-24 3:04 ` Fam Zheng
2015-06-24 9:14 ` Paolo Bonzini
2015-06-24 9:35 ` Stefan Hajnoczi
2015-06-02 3:21 ` [Qemu-devel] [PATCH v2 03/13] blockdev: Lock BDS during internal snapshot transaction Fam Zheng
2015-06-02 3:21 ` [Qemu-devel] [PATCH v2 04/13] blockdev: Lock BDS during external " Fam Zheng
2015-06-02 3:21 ` [Qemu-devel] [PATCH v2 05/13] blockdev: Lock BDS during drive-backup transaction Fam Zheng
2015-06-02 3:21 ` [Qemu-devel] [PATCH v2 06/13] blockdev: Lock BDS during blockdev-backup transaction Fam Zheng
2015-06-02 3:21 ` [Qemu-devel] [PATCH v2 07/13] mirror: Protect source between bdrv_drain and bdrv_swap Fam Zheng
2015-06-02 3:21 ` [Qemu-devel] [PATCH v2 08/13] block: Add bdrv_add_lock_unlock_notifier Fam Zheng
2015-06-02 3:21 ` [Qemu-devel] [PATCH v2 09/13] block-backend: Add blk_add_lock_unlock_notifier Fam Zheng
2015-06-02 3:21 ` [Qemu-devel] [PATCH v2 10/13] virtio-blk: Move complete_request to 'ops' structure Fam Zheng
2015-06-02 3:22 ` [Qemu-devel] [PATCH v2 11/13] virtio-blk: Don't handle output when backend is locked Fam Zheng
2015-06-02 3:22 ` [Qemu-devel] [PATCH v2 12/13] virtio-scsi-dataplane: Add backend lock listener Fam Zheng
2015-06-02 3:22 ` [Qemu-devel] [PATCH v2 13/13] nbd-server: Clear "can_read" when backend is locked Fam Zheng
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