From: Oleg Nesterov <oleg@redhat.com>
To: Roman Gushchin <guroan@gmail.com>
Cc: Tejun Heo <tj@kernel.org>,
cgroups@vger.kernel.org, linux-kernel@vger.kernel.org,
kernel-team@fb.com, Roman Gushchin <guro@fb.com>
Subject: Re: [PATCH v2 3/6] cgroup: cgroup v2 freezer
Date: Tue, 13 Nov 2018 16:48:25 +0100 [thread overview]
Message-ID: <20181113154825.GC30990@redhat.com> (raw)
In-Reply-To: <20181112230422.5911-5-guro@fb.com>
On 11/12, Roman Gushchin wrote:
>
> --- a/include/linux/sched.h
> +++ b/include/linux/sched.h
> @@ -83,7 +83,8 @@ struct task_group;
> #define TASK_WAKING 0x0200
> #define TASK_NOLOAD 0x0400
> #define TASK_NEW 0x0800
> -#define TASK_STATE_MAX 0x1000
> +#define TASK_FROZEN 0x1000
> +#define TASK_STATE_MAX 0x2000
Just noticed the new task state... Why? Can't we avoid it?
...
> +void cgroup_freezer_enter(void)
> +{
> + long state = current->state;
Why? it must be TASK_RUNNING?
If not set_current_state() at the end is simply wrong... Yes, __refrigerator()
does this, but at least it has a reason although it is wrong too.
> + struct cgroup *cgrp;
> +
> + if (!current->frozen) {
> + spin_lock_irq(&css_set_lock);
> + current->frozen = true;
> + cgrp = task_dfl_cgroup(current);
> + cgrp->freezer.nr_frozen_tasks++;
> +
> + WARN_ON_ONCE(cgrp->freezer.nr_tasks_to_freeze <
> + cgrp->freezer.nr_frozen_tasks);
> +
> + if (cgrp->freezer.nr_tasks_to_freeze ==
> + cgrp->freezer.nr_frozen_tasks)
> + cgroup_queue_notify_frozen(cgrp);
> + spin_unlock_irq(&css_set_lock);
> + }
> +
> + /* refrigerator */
> + set_current_state(TASK_WAKEKILL | TASK_INTERRUPTIBLE | TASK_FROZEN);
Why not __set_current_state() ?
If ->state include TASK_INTERRUPTIBLE, why do we need TASK_WAKEKILL?
And again, why TASK_FROZEN?
> + clear_thread_flag(TIF_SIGPENDING);
> + schedule();
> + recalc_sigpending();
I simply can't understand these 3 lines above but I bet this is not correct ;)
if nothing else recalc_sigpending() without ->siglock is wrong, it can race
with signal_wakeup/etc.
> + set_current_state(state);
see above...
Oleg.
next prev parent reply other threads:[~2018-11-13 15:48 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-11-12 23:04 [PATCH v2 0/6] freezer for cgroup v2 Roman Gushchin
2018-11-12 23:04 ` [PATCH] cgroup: document cgroup v2 freezer interface Roman Gushchin
2018-11-12 23:04 ` [PATCH v2 1/6] cgroup: rename freezer.c into legacy_freezer.c Roman Gushchin
2018-11-12 23:04 ` [PATCH v2 2/6] cgroup: implement __cgroup_task_count() helper Roman Gushchin
2018-11-12 23:04 ` [PATCH v2 3/6] cgroup: cgroup v2 freezer Roman Gushchin
2018-11-13 2:08 ` Tejun Heo
2018-11-13 18:47 ` Roman Gushchin
2018-11-13 19:15 ` Tejun Heo
2018-11-13 20:55 ` Roman Gushchin
2018-11-13 20:58 ` Tejun Heo
2018-11-13 15:37 ` Oleg Nesterov
2018-11-13 15:43 ` Tejun Heo
2018-11-13 16:00 ` Oleg Nesterov
2018-11-13 15:48 ` Oleg Nesterov [this message]
2018-11-13 21:59 ` Roman Gushchin
2018-11-14 16:56 ` Oleg Nesterov
2018-11-14 17:06 ` Roman Gushchin
2018-11-14 17:36 ` Oleg Nesterov
2018-11-14 17:39 ` Roman Gushchin
2018-11-28 17:36 ` Roman Gushchin
2018-11-12 23:04 ` [PATCH v2 4/6] kselftests: cgroup: don't fail on cg_kill_all() error in cg_destroy() Roman Gushchin
2018-11-12 23:04 ` [PATCH v2 5/6] kselftests: cgroup: add freezer controller self-tests Roman Gushchin
2018-11-12 23:04 ` [PATCH v2 6/6] cgroup: document cgroup v2 freezer interface Roman Gushchin
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