From: Tejun Heo <tj@kernel.org>
To: Marco Ballesio <balejs@google.com>
Cc: guro@fb.com, cgroups@vger.kernel.org,
linux-kernel@vger.kernel.org, lizefan@huawei.com,
hannes@cmpxchg.org, corbet@lwn.net, rjw@rjwysocki.net,
pavel@ucw.cz, len.brown@intel.com, linux-doc@vger.kernel.org,
linux-pm@vger.kernel.org, minchan@google.com, surenb@google.com,
dancol@google.com
Subject: Re: [PATCH] cgroup-v1: freezer: optionally killable freezer
Date: Tue, 3 Mar 2020 08:48:55 -0500 [thread overview]
Message-ID: <20200303134855.GA186184@mtj.thefacebook.com> (raw)
In-Reply-To: <20200219183231.50985-1-balejs@google.com>
Hello,
On Wed, Feb 19, 2020 at 10:32:31AM -0800, Marco Ballesio wrote:
> @@ -94,6 +94,18 @@ The following cgroupfs files are created by cgroup freezer.
> Shows the parent-state. 0 if none of the cgroup's ancestors is
> frozen; otherwise, 1.
>
> +* freezer.killable: Read-write
> +
> + When read, returns the killable state of a cgroup - "1" if frozen
> + tasks will respond to fatal signals, or "0" if they won't.
> +
> + When written, this property sets the killable state of the cgroup.
> + A value equal to "1" will switch the state of all frozen tasks in
> + the cgroup to TASK_INTERRUPTIBLE (similarly to cgroup v2) and will
> + make them react to fatal signals. A value of "0" will switch the
> + state of frozen tasks to TASK_UNINTERRUPTIBLE and they won't respond
> + to signals unless thawed or unfrozen.
As Roman said, I'm not too sure about adding a new cgroup1 freezer
interface at this point. If we do this, *maybe* a mount option would
be more minimal?
> diff --git a/kernel/freezer.c b/kernel/freezer.c
> index dc520f01f99d..92de1bfe62cf 100644
> --- a/kernel/freezer.c
> +++ b/kernel/freezer.c
> @@ -42,6 +42,9 @@ bool freezing_slow_path(struct task_struct *p)
> if (test_tsk_thread_flag(p, TIF_MEMDIE))
> return false;
>
> + if (cgroup_freezer_killable(p) && fatal_signal_pending(p))
> + return false;
> +
> if (pm_nosig_freezing || cgroup_freezing(p))
> return true;
>
> @@ -63,7 +66,12 @@ bool __refrigerator(bool check_kthr_stop)
> pr_debug("%s entered refrigerator\n", current->comm);
>
> for (;;) {
> - set_current_state(TASK_UNINTERRUPTIBLE);
> + bool killable = cgroup_freezer_killable(current);
> +
> + if (killable)
> + set_current_state(TASK_INTERRUPTIBLE);
> + else
> + set_current_state(TASK_UNINTERRUPTIBLE);
>
> spin_lock_irq(&freezer_lock);
> current->flags |= PF_FROZEN;
> @@ -75,6 +83,16 @@ bool __refrigerator(bool check_kthr_stop)
> if (!(current->flags & PF_FROZEN))
> break;
> was_frozen = true;
> +
> + /*
> + * Now we're sure that there is no pending fatal signal.
> + * Clear TIF_SIGPENDING to not get out of schedule()
> + * immediately (if there is a non-fatal signal pending), and
> + * put the task into sleep.
> + */
and this looks really racy to me. What happens if this task gets a
fatal signal here? We clear TIF_SIGPENDING and go to sleep?
> + if (killable)
> + clear_thread_flag(TIF_SIGPENDING);
> +
> schedule();
> }
Thanks.
--
tejun
next prev parent reply other threads:[~2020-03-03 13:49 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-02-19 18:32 [PATCH] cgroup-v1: freezer: optionally killable freezer Marco Ballesio
2020-02-29 0:51 ` Marco Ballesio
2020-02-29 18:43 ` Roman Gushchin
2020-03-01 16:20 ` Marco Ballesio
2020-03-02 16:53 ` Roman Gushchin
2020-03-02 17:46 ` Suren Baghdasaryan
2020-03-02 18:27 ` Roman Gushchin
2020-03-03 13:48 ` Tejun Heo [this message]
2020-03-11 17:46 ` Daniel Colascione
2020-03-20 20:10 ` Marco Ballesio
2020-03-24 18:26 ` Tejun Heo
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