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From: "Michael S. Tsirkin" <mst@redhat.com>
To: sjur.brandeland@stericsson.com
Cc: "Rusty Russell" <rusty@rustcorp.com.au>,
	"Sjur Brændeland" <sjurbren@gmail.com>,
	linux-kernel@vger.kernel.org, "Guzman Lugo,
	Fernadndo" <fernando.lugo@ti.com>,
	virtualization@lists.linux-foundation.org,
	"Ohad Ben-Cohen" <ohad@wizery.com>
Subject: Re: [PATCH] virtio: Don't access device data after unregistration.
Date: Mon, 3 Sep 2012 17:14:45 +0300	[thread overview]
Message-ID: <20120903141445.GA5054@redhat.com> (raw)
In-Reply-To: <1346680242-5717-1-git-send-email-sjur.brandeland@stericsson.com>

On Mon, Sep 03, 2012 at 03:50:42PM +0200, sjur.brandeland@stericsson.com wrote:
> From: Sjur Brændeland <sjur.brandeland@stericsson.com>
> 
> Fix panic in virtio.c when CONFIG_DEBUG_SLAB is set.

What's the root cause of the panic?


> Use device_del() and put_device() instead of
> device_unregister(), and access device data before
> calling put_device().

Why does this help? Does device_unregister free the
device so dev->index access crashes?
If yes virtio_pci_remove will crash too
as it accesses the device after the
call to unregister_virtio_device so the
fix won't be effective.

> Signed-off-by: Sjur Brændeland <sjur.brandeland@stericsson.com>
> cc: Guzman Lugo, Fernadndo <fernando.lugo@ti.com>
> cc: Michael S. Tsirkin <mst@redhat.com>
> cc: virtualization@lists.linux-foundation.org
> cc: Ohad Ben-Cohen <ohad@wizery.com>
> ---
>  drivers/virtio/virtio.c |    3 ++-
>  1 files changed, 2 insertions(+), 1 deletions(-)
> 
> diff --git a/drivers/virtio/virtio.c b/drivers/virtio/virtio.c
> index c3b3f7f..71eacd1 100644
> --- a/drivers/virtio/virtio.c
> +++ b/drivers/virtio/virtio.c
> @@ -225,8 +225,9 @@ EXPORT_SYMBOL_GPL(register_virtio_device);
>  
>  void unregister_virtio_device(struct virtio_device *dev)
>  {
> -	device_unregister(&dev->dev);
> +	device_del(&dev->dev);
>  	ida_simple_remove(&virtio_index_ida, dev->index);
> +	put_device(&dev->dev);
>  }
>  EXPORT_SYMBOL_GPL(unregister_virtio_device);
>  
> -- 
> 1.7.5.4

  reply	other threads:[~2012-09-03 14:13 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2012-09-03 13:50 sjur.brandeland
2012-09-03 14:14 ` Michael S. Tsirkin [this message]
2012-09-03 14:50   ` Sjur Brændeland
2012-09-03 20:18     ` Michael S. Tsirkin
2012-09-04 12:12       ` Sjur Brændeland
2012-09-04 14:13         ` Michael S. Tsirkin

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