From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Fri, 28 Mar 2003 16:25:08 +0100 (CET) From: Ingo Molnar Reply-To: Ingo Molnar Subject: Re: 2.5.66-mm1 In-Reply-To: Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-linux-mm@kvack.org Return-Path: To: Zwane Mwaikambo Cc: Mike Galbraith , Andrew Morton , Ed Tomlinson , linux-kernel@vger.kernel.org, linux-mm@kvack.org List-ID: On Fri, 28 Mar 2003, Zwane Mwaikambo wrote: > Hmm i think i may have his this one but i never posted due to being > unable to reproduce it on a vanilla kernel or the same kernel afterwards > (which was hacked so i won't vouch for it's cleanliness). I think > preempt might have bitten him in a bad place (mine is also > CONFIG_PREEMPT), is it possible that when we did the task_rq_unlock we > got preempted and when we got back we used the local variable > requeue_waker which was set before dropping the lock, and therefore > might not be valid anymore due to scheduler decisions done after > dropping the runqueue lock? yes, this one was my only suspect, but it should really never cause any problems. We might change sleep_avg during the wakeup, and carry the requeue_waker flag over a preemptible window, but the requeueing itself re-takes the runqueue lock, and does not take anything for granted. The flag could very well be random as well, and the code should still be correct - there's no requirement to recalculate the priority every time we change sleep_avg. (in fact we at times intentionally keep those values detached.) Ingo -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: aart@kvack.org