oom: kill all threads that share mm with killed task

oom_kill_task() calls __oom_kill_task() to OOM kill a selected task.
When finding other threads that share an mm with that task, we need to
kill those individual threads and not the same one.

(Bug introduced by f2a2a71)

Acked-by: William Irwin <[email protected]>
Acked-by: Christoph Lameter <[email protected]>
Cc: Nick Piggin <[email protected]>
Cc: Andrew Morton <[email protected]>
Cc: Andi Kleen <[email protected]>
Signed-off-by: David Rientjes <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

mm/oom_kill.c

@@ -333,7 +333,7 @@ static int oom_kill_task(struct task_struct *p)
 	 */
 	do_each_thread(g, q) {
 		if (q->mm == mm && q->tgid != p->tgid)
-			force_sig(SIGKILL, p);
+			force_sig(SIGKILL, q);
 	} while_each_thread(g, q);
 
 	return 0;