The patch below fixes oom_kill_task() so it doesn't call mmput()
(which may sleep) while holding tasklist_lock.
Signed-Off-By: David S. Peterson <[email protected]>
---
On Friday 14 April 2006 16:52, I wrote:
> Below is a revised version of my previous OOM killer patch. I expect
> to be away from my computer until Monday, 4/24. If you have any
> problems merging this into your tree, let me know and I'll fix things
> up when I get back.
Arrgghh... I sent the wrong patch by mistake. Please ignore the previous
one and merge the patch below instead.
Thanks,
Dave
Index: work/mm/oom_kill.c
===================================================================
--- work.orig/mm/oom_kill.c 2006-04-14 16:21:05.000000000 -0700
+++ work/mm/oom_kill.c 2006-04-14 16:34:31.000000000 -0700
@@ -254,17 +254,24 @@ static void __oom_kill_task(task_t *p, c
force_sig(SIGKILL, p);
}
-static struct mm_struct *oom_kill_task(task_t *p, const char *message)
+static int oom_kill_task(task_t *p, const char *message)
{
- struct mm_struct *mm = get_task_mm(p);
+ struct mm_struct *mm;
task_t * g, * q;
- if (!mm)
- return NULL;
- if (mm == &init_mm) {
- mmput(mm);
- return NULL;
- }
+ mm = p->mm;
+
+ /* WARNING: mm may not be dereferenced since we did not obtain its
+ * value from get_task_mm(p). This is OK since all we need to do is
+ * compare mm to q->mm below.
+ *
+ * Furthermore, even if mm contains a non-NULL value, p->mm may
+ * change to NULL at any time since we do not hold task_lock(p).
+ * However, this is of no concern to us.
+ */
+
+ if (mm == NULL || mm == &init_mm)
+ return 1;
__oom_kill_task(p, message);
/*
@@ -276,13 +283,12 @@ static struct mm_struct *oom_kill_task(t
__oom_kill_task(q, message);
while_each_thread(g, q);
- return mm;
+ return 0;
}
-static struct mm_struct *oom_kill_process(struct task_struct *p,
- unsigned long points, const char *message)
+static int oom_kill_process(struct task_struct *p, unsigned long points,
+ const char *message)
{
- struct mm_struct *mm;
struct task_struct *c;
struct list_head *tsk;
@@ -293,9 +299,8 @@ static struct mm_struct *oom_kill_proces
c = list_entry(tsk, struct task_struct, sibling);
if (c->mm == p->mm)
continue;
- mm = oom_kill_task(c, message);
- if (mm)
- return mm;
+ if (!oom_kill_task(c, message))
+ return 0;
}
return oom_kill_task(p, message);
}
@@ -310,7 +315,6 @@ static struct mm_struct *oom_kill_proces
*/
void out_of_memory(struct zonelist *zonelist, gfp_t gfp_mask, int order)
{
- struct mm_struct *mm = NULL;
task_t *p;
unsigned long points = 0;
@@ -330,12 +334,12 @@ void out_of_memory(struct zonelist *zone
*/
switch (constrained_alloc(zonelist, gfp_mask)) {
case CONSTRAINT_MEMORY_POLICY:
- mm = oom_kill_process(current, points,
+ oom_kill_process(current, points,
"No available memory (MPOL_BIND)");
break;
case CONSTRAINT_CPUSET:
- mm = oom_kill_process(current, points,
+ oom_kill_process(current, points,
"No available memory in cpuset");
break;
@@ -357,8 +361,7 @@ retry:
panic("Out of memory and no killable processes...\n");
}
- mm = oom_kill_process(p, points, "Out of memory");
- if (!mm)
+ if (oom_kill_process(p, points, "Out of memory"))
goto retry;
break;
@@ -367,8 +370,6 @@ retry:
out:
read_unlock(&tasklist_lock);
cpuset_unlock();
- if (mm)
- mmput(mm);
/*
* Give "p" a good chance of killing itself before we
-
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