[PATCH] elv_unregister: fix possible crash on module unload

From: Oleg Nesterov
Date: Tue Aug 22 2006 - 08:55:27 EST


An exiting task or process which didn't do I/O yet have no io context,
elv_unregister() should check it is not NULL.

Signed-off-by: Oleg Nesterov <oleg@xxxxxxxxxx>

--- 2.6.18-rc4/block/elevator.c~8_crash 2006-07-16 01:53:08.000000000 +0400
+++ 2.6.18-rc4/block/elevator.c 2006-08-22 21:13:06.000000000 +0400
@@ -765,7 +765,8 @@ void elv_unregister(struct elevator_type
read_lock(&tasklist_lock);
do_each_thread(g, p) {
task_lock(p);
- e->ops.trim(p->io_context);
+ if (p->io_context)
+ e->ops.trim(p->io_context);
task_unlock(p);
} while_each_thread(g, p);
read_unlock(&tasklist_lock);

-
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