lkml.org 
[lkml]   [2017]   [Jul]   [28]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: [PATCH] xen: avoid deadlock in xenbus
From
Date
On 28/07/17 17:14, Boris Ostrovsky wrote:
> On 07/28/2017 10:53 AM, Juergen Gross wrote:
>> When starting the xenwatch thread a theoretical deadlock situation is
>> possible:
>>
>> xs_init() contains:
>>
>> task = kthread_run(xenwatch_thread, NULL, "xenwatch");
>> if (IS_ERR(task))
>> return PTR_ERR(task);
>> xenwatch_pid = task->pid;
>>
>> And xenwatch_thread() does:
>>
>> mutex_lock(&xenwatch_mutex);
>> ...
>> event->handle->callback();
>> ...
>> mutex_unlock(&xenwatch_mutex);
>>
>> The callback could call unregister_xenbus_watch() which does:
>>
>> ...
>> if (current->pid != xenwatch_pid)
>> mutex_lock(&xenwatch_mutex);
>> ...
>>
>> In case a watch is firing before xenwatch_pid could be set and the
>> callback of that watch unregisters a watch, then a self-deadlock would
>> occur.
>>
>> Avoid this by setting xenwatch_pid in xenwatch_thread().
>>
>> Signed-off-by: Juergen Gross <jgross@suse.com>
>
> Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
>
> +stable?

As this problem is purely theoretical, I don't think the patch is
appropriate for stable (at least the stable rules tell me so).


Juergen

\
 
 \ /
  Last update: 2017-07-28 17:17    [W:0.060 / U:15.736 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site