Commit 50ec3bbf authored by Nicholas Piggin's avatar Nicholas Piggin Committed by Linus Torvalds
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[PATCH] oom: handle current exiting 



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: default avatarNick Piggin <npiggin@suse.de>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent 7887a3da

mm/oom_kill.c

+31 −4
Original line number Diff line number Diff line
@@ -210,11 +210,26 @@ static struct task_struct *select_bad_process(unsigned long *ppoints) 
		/*

		 * 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;
@@ -248,8 +263,11 @@ static void __oom_kill_task(struct task_struct *p, const char *message) 
		return;

	}

	task_unlock(p);



	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
@@ -300,8 +318,17 @@ static int oom_kill_process(struct task_struct *p, unsigned long points, 
	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);