Re: [Xen-devel] [PATCH] Fix blkback/blktap sysfs read bug.

To:	"Joe Jin" <joe.jin@xxxxxxxxxx>
Subject:	Re: [Xen-devel] [PATCH] Fix blkback/blktap sysfs read bug.
From:	"Jan Beulich" <JBeulich@xxxxxxxxxx>
Date:	Wed, 20 Jan 2010 11:06:14 +0000
Cc:	Keir Fraser <keir.fraser@xxxxxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxx, deepak.patel@xxxxxxxxxx, greg.marsden@xxxxxxxxxx
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>>> "Joe Jin" <joe.jin@xxxxxxxxxx> 20.01.10 11:51 >>>
>On 2010-01-20 07:46, Jan Beulich wrote:
>> And btw., in both cases with the lock added there's no need to check
>> both 'be' and 'be->blkif', since be->blkif can't be NULL when be is
>> non-NULL.
>
>No we must check it, as I have methioned, root cause is vbd was been
>freed after open sysfs file.

Why? You're inside the locked region, so either 'be' is NULL, or both
'be' and 'be->blkif' are non-NULL.

Jan


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Re: [Xen-devel] [PATCH] Fix blkback/blktap sysfs read bug.