diff options
| author | Juergen Gross <jgross@suse.com> | 2017-07-28 16:53:55 +0200 |
|---|---|---|
| committer | Juergen Gross <jgross@suse.com> | 2017-08-11 16:45:56 +0200 |
| commit | 529871bb3c0675d0b425e2070d5a739db097be98 (patch) | |
| tree | 0422815a0e9fe13f44bebde0046b768569ea36e9 | |
| parent | 4ca83dcf4e3bc0c98836dbb97553792ca7ea5429 (diff) | |
xen: avoid deadlock in xenbus
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>
| -rw-r--r-- | drivers/xen/xenbus/xenbus_xs.c | 3 |
1 files changed, 2 insertions, 1 deletions
diff --git a/drivers/xen/xenbus/xenbus_xs.c b/drivers/xen/xenbus/xenbus_xs.c index e46080214955..3e59590c7254 100644 --- a/drivers/xen/xenbus/xenbus_xs.c +++ b/drivers/xen/xenbus/xenbus_xs.c @@ -857,6 +857,8 @@ static int xenwatch_thread(void *unused) struct list_head *ent; struct xs_watch_event *event; + xenwatch_pid = current->pid; + for (;;) { wait_event_interruptible(watch_events_waitq, !list_empty(&watch_events)); @@ -925,7 +927,6 @@ int xs_init(void) task = kthread_run(xenwatch_thread, NULL, "xenwatch"); if (IS_ERR(task)) return PTR_ERR(task); - xenwatch_pid = task->pid; /* shutdown watches for kexec boot */ xs_reset_watches(); |