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[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 <npiggin@suse.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
hifive-unleashed-5.1
Nick Piggin 2006-09-29 02:01:14 -07:00 committed by Linus Torvalds
parent 01017a2270
commit b78483a4ba
1 changed files with 17 additions and 6 deletions
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23
mm/oom_kill.c
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@ -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;