From: Stefan Hajnoczi <stefanha@redhat.com>
To: Maxim Levitsky <mlevitsk@redhat.com>
Cc: "Fam Zheng" <fam@euphon.net>,
"Daniel P. Berrangé" <berrange@redhat.com>,
"Eduardo Habkost" <ehabkost@redhat.com>,
"Michael S. Tsirkin" <mst@redhat.com>,
qemu-devel@nongnu.org, "Paolo Bonzini" <pbonzini@redhat.com>
Subject: Re: [PATCH v3 4/7] device-core: use atomic_set on .realized property
Date: Wed, 5 Aug 2020 11:33:26 +0100 [thread overview]
Message-ID: <20200805103326.GB361702@stefanha-x1.localdomain> (raw)
In-Reply-To: <20200715150159.95050-5-mlevitsk@redhat.com>
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On Wed, Jul 15, 2020 at 06:01:56PM +0300, Maxim Levitsky wrote:
> Some code might race with placement of new devices on a bus.
> We currently first place a (unrealized) device on the bus
> and then realize it.
>
> As a workaround, users that scan the child device list, can
> check the realized property to see if it is safe to access such a device.
> Use an atomic write here too to aid with this.
>
> A separate discussion is what to do with devices that are unrealized:
> It looks like for this case we only call the hotplug handler's unplug
> callback and its up to it to unrealize the device.
> An atomic operation doesn't cause harm for this code path though.
>
> Signed-off-by: Maxim Levitsky <mlevitsk@redhat.com>
> ---
> hw/core/qdev.c | 19 ++++++++++++++++++-
> include/hw/qdev-core.h | 2 ++
> 2 files changed, 20 insertions(+), 1 deletion(-)
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
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next prev parent reply other threads:[~2020-08-05 10:34 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-07-15 15:01 [PATCH v3 0/7] Fix scsi devices plug/unplug races w.r.t virtio-scsi iothread Maxim Levitsky
2020-07-15 15:01 ` [PATCH v3 1/7] scsi/scsi_bus: switch search direction in scsi_device_find Maxim Levitsky
2020-07-15 15:01 ` [PATCH v3 2/7] Implement drain_call_rcu and use it in hmp_device_del Maxim Levitsky
2020-07-15 15:01 ` [PATCH v3 3/7] device-core: use RCU for list of childs of a bus Maxim Levitsky
2020-08-05 10:32 ` Stefan Hajnoczi
2020-07-15 15:01 ` [PATCH v3 4/7] device-core: use atomic_set on .realized property Maxim Levitsky
2020-08-05 10:33 ` Stefan Hajnoczi [this message]
2020-07-15 15:01 ` [PATCH v3 5/7] virtio-scsi: don't touch scsi devices that are not yet realized or about to be un-realized Maxim Levitsky
2020-07-15 15:01 ` [PATCH v3 6/7] scsi: Add scsi_device_get Maxim Levitsky
2020-08-05 10:45 ` Stefan Hajnoczi
2020-07-15 15:01 ` [PATCH v3 7/7] virtio-scsi: use scsi_device_get Maxim Levitsky
2020-07-29 19:56 ` [PATCH v3 0/7] Fix scsi devices plug/unplug races w.r.t virtio-scsi iothread Maxim Levitsky
2020-08-05 10:48 ` Stefan Hajnoczi
2020-08-13 12:26 ` Maxim Levitsky
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