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From: "Michael S. Tsirkin" <mst@redhat.com>
To: linux-kernel@vger.kernel.org
Cc: Amit Shah <amit@kernel.org>, Arnd Bergmann <arnd@arndb.de>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	virtualization@lists.linux-foundation.org
Subject: [PATCH] virtio_console: break out of buf poll on remove
Date: Tue, 5 Oct 2021 03:04:07 -0400	[thread overview]
Message-ID: <20211005070354.265164-1-mst@redhat.com> (raw)

A common pattern for device reset is currently:
vdev->config->reset(vdev);
.. cleanup ..

reset prevents new interrupts from arriving and waits for interrupt
handlers to finish.

However if - as is common - the handler queues a work request which is
flushed during the cleanup stage, we have code adding buffers / trying
to get buffers while device is reset. Not good.

This was reproduced by running
	modprobe virtio_console
	modprobe -r virtio_console
in a loop.

Fixing this comprehensively needs some thought, and new APIs.
Let's at least handle the specific case of virtio_console
removal that was reported in the field.

Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=1786239
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
---
 drivers/char/virtio_console.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/char/virtio_console.c b/drivers/char/virtio_console.c
index 7eaf303a7a86..c852ce0b4d56 100644
--- a/drivers/char/virtio_console.c
+++ b/drivers/char/virtio_console.c
@@ -1956,6 +1956,12 @@ static void virtcons_remove(struct virtio_device *vdev)
 	list_del(&portdev->list);
 	spin_unlock_irq(&pdrvdata_lock);
 
+	/* Device is going away, exit any polling for buffers */
+	virtio_break_device(vdev);
+	if (use_multiport(portdev))
+		flush_work(&portdev->control_work);
+	else
+		flush_work(&portdev->config_work);
 	/* Disable interrupts for vqs */
 	vdev->config->reset(vdev);
 	/* Finish up work that's lined up */
-- 
MST


WARNING: multiple messages have this Message-ID (diff)
From: "Michael S. Tsirkin" <mst@redhat.com>
To: linux-kernel@vger.kernel.org
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	virtualization@lists.linux-foundation.org,
	Arnd Bergmann <arnd@arndb.de>, Amit Shah <amit@kernel.org>
Subject: [PATCH] virtio_console: break out of buf poll on remove
Date: Tue, 5 Oct 2021 03:04:07 -0400	[thread overview]
Message-ID: <20211005070354.265164-1-mst@redhat.com> (raw)

A common pattern for device reset is currently:
vdev->config->reset(vdev);
.. cleanup ..

reset prevents new interrupts from arriving and waits for interrupt
handlers to finish.

However if - as is common - the handler queues a work request which is
flushed during the cleanup stage, we have code adding buffers / trying
to get buffers while device is reset. Not good.

This was reproduced by running
	modprobe virtio_console
	modprobe -r virtio_console
in a loop.

Fixing this comprehensively needs some thought, and new APIs.
Let's at least handle the specific case of virtio_console
removal that was reported in the field.

Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=1786239
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
---
 drivers/char/virtio_console.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/char/virtio_console.c b/drivers/char/virtio_console.c
index 7eaf303a7a86..c852ce0b4d56 100644
--- a/drivers/char/virtio_console.c
+++ b/drivers/char/virtio_console.c
@@ -1956,6 +1956,12 @@ static void virtcons_remove(struct virtio_device *vdev)
 	list_del(&portdev->list);
 	spin_unlock_irq(&pdrvdata_lock);
 
+	/* Device is going away, exit any polling for buffers */
+	virtio_break_device(vdev);
+	if (use_multiport(portdev))
+		flush_work(&portdev->control_work);
+	else
+		flush_work(&portdev->config_work);
 	/* Disable interrupts for vqs */
 	vdev->config->reset(vdev);
 	/* Finish up work that's lined up */
-- 
MST

_______________________________________________
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Virtualization@lists.linux-foundation.org
https://lists.linuxfoundation.org/mailman/listinfo/virtualization

             reply	other threads:[~2021-10-05  7:04 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-10-05  7:04 Michael S. Tsirkin [this message]
2021-10-05  7:04 ` [PATCH] virtio_console: break out of buf poll on remove Michael S. Tsirkin
2021-10-05 13:33 ` Greg Kroah-Hartman
2021-10-05 13:33   ` Greg Kroah-Hartman
2022-01-14 21:48   ` Michael S. Tsirkin
2022-01-14 21:48     ` Michael S. Tsirkin

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