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4369ef3c3e
Applying RCU to the task structure broke oprofile, because free_task_notify() can now be called from softirq. This means that the task_mortuary lock must be acquired with irq disabled in order to avoid intermittent self-deadlock. Since irq is now disabled, the critical section within process_task_mortuary() has been restructured to be O(1) in order to maximize scalability and minimize realtime latency degradation. Kudos to Wu Fengguang for finding this problem! CC: Wu Fengguang <wfg@mail.ustc.edu.cn> Cc: Philippe Elie <phil.el@wanadoo.fr> Cc: John Levon <levon@movementarian.org> Signed-off-by: "Paul E. McKenney" <paulmck@us.ibm.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>