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>
Signed-off-by: Juergen Gross <jgross@suse.com>
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