On Tuesday, October 21, 2014 04:11:59 PM Michal Hocko wrote:
> 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
Yes, I am.
> ---
> 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.");
> }
>
--
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.
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