Commit 50ec3bbf authored by Nick Piggin's avatar Nick 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
......@@ -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);
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
......@@ -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);
......
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