On Mon, 31 May 2010 18:36:34 +0900 (JST) KOSAKI Motohiro <kosaki.motohiro@xxxxxxxxxxxxxx> wrote: > From: Oleg Nesterov <oleg@xxxxxxxxxx> > Subject: [PATCH 3/5] oom: introduce find_lock_task_mm() to fix !mm false positives > > Almost all ->mm == NUL checks in oom_kill.c are wrong. > > The current code assumes that the task without ->mm has already > released its memory and ignores the process. However this is not > necessarily true when this process is multithreaded, other live > sub-threads can use this ->mm. > > - Remove the "if (!p->mm)" check in select_bad_process(), it is > just wrong. > > - Add the new helper, find_lock_task_mm(), which finds the live > thread which uses the memory and takes task_lock() to pin ->mm > > - change oom_badness() to use this helper instead of just checking > ->mm != NULL. > > - As David pointed out, select_bad_process() must never choose the > task without ->mm, but no matter what badness() returns the > task can be chosen if nothing else has been found yet. > > Note! This patch is not enough, we need more changes. > > - badness() was fixed, but oom_kill_task() still ignores > the task without ->mm > > This will be addressed later. > > Signed-off-by: Oleg Nesterov <oleg@xxxxxxxxxx> > Cc: David Rientjes <rientjes@xxxxxxxxxx> > Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@xxxxxxxxxxxxxx> [rebase > latest -mm and remove some obsoleted description] Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx> -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxxx For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>