On Tue 21-10-14 15:42:23, Rafael J. Wysocki wrote:
> On Tuesday, October 21, 2014 03:14:45 PM Michal Hocko wrote:
> > On Tue 21-10-14 14:09:27, Rafael J. Wysocki wrote:
> > [...]
> > > > @@ -131,12 +132,40 @@ int freeze_processes(void)
> > > >
> > > > printk("Freezing user space processes ... ");
> > > > pm_freezing = true;
> > > > + oom_kills_saved = oom_kills_count();
> > > > error = try_to_freeze_tasks(true);
> > > > if (!error) {
> > > > - printk("done.");
> > > > __usermodehelper_set_disable_depth(UMH_DISABLED);
> > > > oom_killer_disable();
> > > > +
> > > > + /*
> > > > + * There might have been an OOM kill while we were
> > > > + * freezing tasks and the killed task might be still
> > > > + * on the way out so we have to double check for race.
> > > > + */
> > > > + if (oom_kills_count() != oom_kills_saved) {
> > > > + struct task_struct *g, *p;
> > > > +
> > > > + read_lock(&tasklist_lock);
> > > > + for_each_process_thread(g, p) {
> > > > + if (p == current ||
> > > > freezer_should_skip(p) ||
> > > > + frozen(p))
> > > > + continue;
> > > > + error = -EBUSY;
> > > > + goto out_loop;
> > > > + }
> > > > +out_loop:
> > >
> > > Well, it looks like this will work here too:
> > >
> > > for_each_process_thread(g, p)
> > > if (p != current && !frozen(p) &&
> > > !freezer_should_skip(p)) {
> > > error = -EBUSY;
> > > break;
> > > }
> > >
> > > or I am helplessly misreading the code.
> >
> > break will not work because for_each_process_thread is a double loop.
>
> I see. In that case I'd do:
>
> for_each_process_thread(g, p)
> if (p != current && !frozen(p) &&
> !freezer_should_skip(p)) {
>
> read_unlock(&tasklist_lock);
>
>
> __usermodehelper_set_disable_depth(UMH_ENABLED);
> printk("OOM in progress.");
> error = -EBUSY;
> goto done;
> }
>
> to avoid adding the new label that looks odd.
OK, incremental diff on top. I will post the complete patch if you are
happier with this change
---
diff --git a/kernel/power/process.c b/kernel/power/process.c
index a397fa161d11..7a37cf3eb1a2 100644
--- a/kernel/power/process.c
+++ b/kernel/power/process.c
@@ -108,6 +108,28 @@ static int try_to_freeze_tasks(bool user_only)
return todo ? -EBUSY : 0;
}
+/*
+ * Returns true if all freezable tasks (except for current) are frozen already
+ */
+static bool check_frozen_processes(void)
+{
+ struct task_struct *g, *p;
+ bool ret = true;
+
+ read_lock(&tasklist_lock);
+ for_each_process_thread(g, p) {
+ if (p != current && !freezer_should_skip(p) &&
+ !frozen(p)) {
+ ret = false;
+ goto done;
+ }
+ }
+done:
+ read_unlock(&tasklist_lock);
+
+ return ret;
+}
+
/**
* freeze_processes - Signal user space processes to enter the refrigerator.
* The current thread will not be frozen. The same process that calls
@@ -143,25 +165,12 @@ int freeze_processes(void)
* freezing tasks and the killed task might be still
* on the way out so we have to double check for race.
*/
- if (oom_kills_count() != oom_kills_saved) {
- struct task_struct *g, *p;
-
- read_lock(&tasklist_lock);
- for_each_process_thread(g, p) {
- if (p == current || freezer_should_skip(p) ||
- frozen(p))
- continue;
- error = -EBUSY;
- goto out_loop;
- }
-out_loop:
- read_unlock(&tasklist_lock);
-
- if (error) {
- __usermodehelper_set_disable_depth(UMH_ENABLED);
- printk("OOM in progress.");
- goto done;
- }
+ if (oom_kills_count() != oom_kills_saved &&
+ !check_frozen_processes()) {
+ __usermodehelper_set_disable_depth(UMH_ENABLED);
+ printk("OOM in progress.");
+ error = -EBUSY;
+ goto done;
}
printk("done.");
}
--
Michal Hocko
SUSE Labs
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