[PATCH] fix wait_task_inactive race

[PATCH] fix wait_task_inactive race

When a task is put to sleep, it is dequeued from the runqueue while it is
still running.  The problem is that one some arches that have non-atomic
scheduling, the runqueue lock can be dropped and retaken in schedule() before
the task actually schedules off, and wait_task_inactive did not account for
this.

Signed-off-by: Nick Piggin <nickpiggin@yahoo.com.au>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>