From: "Rafael J. Wysocki" <rjw@rjwysocki.net>
To: Michal Hocko <mhocko@suse.cz>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Cong Wang <xiyou.wangcong@gmail.com>,
David Rientjes <rientjes@google.com>, Tejun Heo <tj@kernel.org>,
Oleg Nesterov <oleg@redhat.com>,
LKML <linux-kernel@vger.kernel.org>,
linux-mm@kvack.org, Linux PM list <linux-pm@vger.kernel.org>
Subject: Re: [PATCH 3/4] OOM, PM: OOM killed task shouldn't escape PM suspend
Date: Tue, 21 Oct 2014 16:41:07 +0200 [thread overview]
Message-ID: <4766859.KSKPTm3b0x@vostro.rjw.lan> (raw)
In-Reply-To: <20141021141159.GE9415@dhcp22.suse.cz>
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.
next prev parent reply other threads:[~2014-10-21 14:20 UTC|newest]
Thread overview: 93+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-10-21 7:27 [PATCH 0/4 -v2] OOM vs. freezer interaction fixes Michal Hocko
2014-10-21 7:27 ` [PATCH 1/4] freezer: Do not freeze tasks killed by OOM killer Michal Hocko
2014-10-21 12:04 ` Rafael J. Wysocki
2014-10-21 7:27 ` [PATCH 2/4] freezer: remove obsolete comments in __thaw_task() Michal Hocko
2014-10-21 12:04 ` Rafael J. Wysocki
2014-10-21 7:27 ` [PATCH 3/4] OOM, PM: OOM killed task shouldn't escape PM suspend Michal Hocko
2014-10-21 12:09 ` Rafael J. Wysocki
2014-10-21 13:14 ` Michal Hocko
2014-10-21 13:42 ` Rafael J. Wysocki
2014-10-21 14:11 ` Michal Hocko
2014-10-21 14:41 ` Rafael J. Wysocki [this message]
2014-10-21 14:29 ` Michal Hocko
2014-10-22 14:39 ` Rafael J. Wysocki
2014-10-22 14:22 ` Michal Hocko
2014-10-22 21:18 ` Rafael J. Wysocki
2014-10-26 18:49 ` Pavel Machek
2014-11-04 19:27 ` Tejun Heo
2014-11-05 12:46 ` Michal Hocko
2014-11-05 13:02 ` Tejun Heo
2014-11-05 13:31 ` Michal Hocko
2014-11-05 13:42 ` Michal Hocko
2014-11-05 14:14 ` Michal Hocko
2014-11-05 15:45 ` Michal Hocko
2014-11-05 15:44 ` Tejun Heo
2014-11-05 16:01 ` Michal Hocko
2014-11-05 16:29 ` Tejun Heo
2014-11-05 16:39 ` Michal Hocko
2014-11-05 16:54 ` Tejun Heo
2014-11-05 17:01 ` Tejun Heo
2014-11-06 13:05 ` Michal Hocko
2014-11-06 15:09 ` Tejun Heo
2014-11-06 16:01 ` Michal Hocko
2014-11-06 16:12 ` Tejun Heo
2014-11-06 16:31 ` Michal Hocko
2014-11-06 16:33 ` Tejun Heo
2014-11-06 16:58 ` Michal Hocko
2014-11-05 17:46 ` Michal Hocko
2014-11-05 17:55 ` Tejun Heo
2014-11-06 12:49 ` Michal Hocko
2014-11-06 15:01 ` Tejun Heo
2014-11-06 16:02 ` Michal Hocko
2014-11-06 16:28 ` Tejun Heo
2014-11-10 16:30 ` Michal Hocko
2014-11-12 18:58 ` [RFC 0/4] OOM vs PM freezer fixes Michal Hocko
2014-11-12 18:58 ` [RFC 1/4] OOM, PM: Do not miss OOM killed frozen tasks Michal Hocko
2014-11-14 17:55 ` Tejun Heo
2014-11-12 18:58 ` [RFC 2/4] OOM, PM: make OOM detection in the freezer path raceless Michal Hocko
2014-11-12 18:58 ` [RFC 3/4] OOM, PM: handle pm freezer as an OOM victim correctly Michal Hocko
2014-11-12 18:58 ` [RFC 4/4] OOM: thaw the OOM victim if it is frozen Michal Hocko
2014-11-14 20:14 ` [RFC 0/4] OOM vs PM freezer fixes Tejun Heo
2014-11-18 21:08 ` Michal Hocko
2014-11-18 21:10 ` [RFC 1/2] oom: add helper for setting and clearing TIF_MEMDIE Michal Hocko
2014-11-18 21:10 ` [RFC 2/2] OOM, PM: make OOM detection in the freezer path raceless Michal Hocko
2014-11-27 0:47 ` Rafael J. Wysocki
2014-12-02 22:08 ` Tejun Heo
2014-12-04 14:16 ` Michal Hocko
2014-12-04 14:44 ` Tejun Heo
2014-12-04 16:56 ` Michal Hocko
2014-12-04 17:18 ` Michal Hocko
2014-12-05 16:41 ` [PATCH 0/4] OOM vs PM freezer fixes Michal Hocko
2014-12-05 16:41 ` [PATCH -v2 1/5] oom: add helpers for setting and clearing TIF_MEMDIE Michal Hocko
2014-12-06 12:56 ` Tejun Heo
2014-12-07 10:13 ` Michal Hocko
2015-01-07 17:57 ` Tejun Heo
2015-01-07 18:23 ` Michal Hocko
2014-12-05 16:41 ` [PATCH -v2 2/5] OOM: thaw the OOM victim if it is frozen Michal Hocko
2014-12-06 13:06 ` Tejun Heo
2014-12-07 10:24 ` Michal Hocko
2014-12-07 10:45 ` Michal Hocko
2014-12-07 13:59 ` Tejun Heo
2014-12-07 18:55 ` Michal Hocko
2014-12-05 16:41 ` [PATCH -v2 3/5] PM: convert printk to pr_* equivalent Michal Hocko
2014-12-05 22:40 ` Rafael J. Wysocki
2014-12-07 10:26 ` Michal Hocko
2014-12-06 13:08 ` Tejun Heo
2014-12-05 16:41 ` [PATCH -v2 4/5] sysrq: " Michal Hocko
2014-12-06 13:09 ` Tejun Heo
2014-12-05 16:41 ` [PATCH -v2 5/5] OOM, PM: make OOM detection in the freezer path raceless Michal Hocko
2014-12-06 13:11 ` Tejun Heo
2014-12-07 10:11 ` Michal Hocko
2015-01-07 18:41 ` Tejun Heo
2015-01-07 18:48 ` Michal Hocko
2015-01-08 11:51 ` Michal Hocko
2014-12-07 10:09 ` [PATCH 0/4] OOM vs PM freezer fixes Michal Hocko
2014-12-07 13:55 ` Tejun Heo
2014-12-07 19:00 ` Michal Hocko
2014-12-18 16:27 ` Michal Hocko
2014-11-05 14:55 ` [PATCH 3/4] OOM, PM: OOM killed task shouldn't escape PM suspend Michal Hocko
2014-10-26 18:40 ` Pavel Machek
2014-10-21 7:27 ` [PATCH 4/4] PM: convert do_each_thread to for_each_process_thread Michal Hocko
2014-10-21 12:10 ` Rafael J. Wysocki
2014-10-21 13:19 ` Michal Hocko
2014-10-21 13:43 ` Rafael J. Wysocki
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