From b78483a4ba60d5d90930262a533a784e1d9df660 Mon Sep 17 00:00:00 2001 From: Nick Piggin Date: Fri, 29 Sep 2006 02:01:14 -0700 Subject: [PATCH] [PATCH] oom: don't kill current when another OOM in progress A previous patch to allow an exiting task to OOM kill itself (and thereby avoid a little deadlock) introduced a problem. We don't want the PF_EXITING task, even if it is 'current', to access mem reserves if there is already a TIF_MEMDIE process in the system sucking up reserves. Also make the commenting a little bit clearer, and note that our current scheme of effectively single threading the OOM killer is not itself perfect. Signed-off-by: Nick Piggin Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/oom_kill.c | 23 +++++++++++++++++------ 1 file changed, 17 insertions(+), 6 deletions(-) diff --git a/mm/oom_kill.c b/mm/oom_kill.c index a5493a3b4851..20f41b082e16 100644 --- a/mm/oom_kill.c +++ b/mm/oom_kill.c @@ -215,6 +215,18 @@ static struct task_struct *select_bad_process(unsigned long *ppoints) if (is_init(p)) continue; + /* + * This task already has access to memory reserves and is + * being killed. Don't allow any other task access to the + * memory reserve. + * + * Note: this may have a chance of deadlock if it gets + * blocked waiting for another task which itself is waiting + * for memory. Is there a better alternative? + */ + if (test_tsk_thread_flag(p, TIF_MEMDIE)) + return ERR_PTR(-1UL); + /* * This is in the process of releasing memory so wait for it * to finish before killing some other task by mistake. @@ -223,16 +235,15 @@ static struct task_struct *select_bad_process(unsigned long *ppoints) * go ahead if it is exiting: this will simply set TIF_MEMDIE, * which will allow it to gain access to memory reserves in * the process of exiting and releasing its resources. - * Otherwise we could get an OOM deadlock. + * Otherwise we could get an easy OOM deadlock. */ - if ((p->flags & PF_EXITING) && p == current) { + if (p->flags & PF_EXITING) { + if (p != current) + return ERR_PTR(-1UL); + chosen = p; *ppoints = ULONG_MAX; - break; } - if ((p->flags & PF_EXITING) || - test_tsk_thread_flag(p, TIF_MEMDIE)) - return ERR_PTR(-1UL); if (p->oomkilladj == OOM_DISABLE) continue;