From mboxrd@z Thu Jan 1 00:00:00 1970 From: Nick Piggin Message-Id: <20060515210614.30275.39068.sendpatchset@linux.site> In-Reply-To: <20060515210529.30275.74992.sendpatchset@linux.site> References: <20060515210529.30275.74992.sendpatchset@linux.site> Subject: [patch 5/9] oom: handle current exiting Date: Fri, 28 Jul 2006 09:21:28 +0200 (CEST) Sender: owner-linux-mm@kvack.org Return-Path: To: Andrew Morton Cc: Nick Piggin , Linux Memory Management List-ID: If current *is* exiting, it should actually be allowed to access reserved memory rather than OOM kill something else. Can't do this via a straight check in page_alloc.c because that would allow multiple tasks to use up reserves. Instead cause current to OOM-kill itself which will mark it as TIF_MEMDIE. The current procedure of simply aborting the OOM-kill if a task is exiting can lead to OOM deadlocks. In the case of killing a PF_EXITING task, don't make a lot of noise about it. This becomes more important in future patches, where we can "kill" OOM_DISABLE tasks. Signed-off-by: Nick Piggin Index: linux-2.6/mm/oom_kill.c =================================================================== --- linux-2.6.orig/mm/oom_kill.c +++ linux-2.6/mm/oom_kill.c @@ -208,11 +208,26 @@ static struct task_struct *select_bad_pr /* * This is in the process of releasing memory so wait for it * to finish before killing some other task by mistake. + * + * However, if p is the current task, we allow the 'kill' to + * 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. */ releasing = test_tsk_thread_flag(p, TIF_MEMDIE) || p->flags & PF_EXITING; - if (releasing && !(p->flags & PF_DEAD)) + if (releasing) { + /* PF_DEAD tasks have already released their mm */ + if (p->flags & PF_DEAD) + continue; + if (p->flags & PF_EXITING && p == current) { + chosen = p; + *ppoints = ULONG_MAX; + break; + } return ERR_PTR(-1UL); + } if (p->flags & PF_SWAPOFF) return p; @@ -246,8 +261,11 @@ static void __oom_kill_task(struct task_ return; } task_unlock(p); - printk(KERN_ERR "%s: Killed process %d (%s).\n", + + if (message) { + printk(KERN_ERR "%s: Killed process %d (%s).\n", message, p->pid, p->comm); + } /* * We give our sacrificial lamb high priority and access to @@ -298,8 +316,17 @@ static int oom_kill_process(struct task_ struct task_struct *c; struct list_head *tsk; - printk(KERN_ERR "Out of Memory: Kill process %d (%s) score %li and " - "children.\n", p->pid, p->comm, points); + /* + * If the task is already exiting, don't alarm the sysadmin or kill + * its children or threads, just set TIF_MEMDIE so it can die quickly + */ + if (p->flags & PF_EXITING) { + __oom_kill_task(p, NULL); + return 0; + } + + printk(KERN_ERR "Out of Memory: Kill process %d (%s) score %li" + " and children.\n", p->pid, p->comm, points); /* Try to kill a child first */ list_for_each(tsk, &p->children) { c = list_entry(tsk, struct task_struct, sibling); -- 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: email@kvack.org