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From: Oleg Nesterov <oleg@redhat.com>
To: Roman Gushchin <guro@fb.com>
Cc: Roman Gushchin <guroan@gmail.com>, Tejun Heo <tj@kernel.org>,
	Kernel Team <Kernel-team@fb.com>,
	"cgroups@vger.kernel.org" <cgroups@vger.kernel.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v8 4/7] cgroup: cgroup v2 freezer
Date: Thu, 21 Feb 2019 17:44:04 +0100	[thread overview]
Message-ID: <20190221164403.GB26064@redhat.com> (raw)
In-Reply-To: <20190220221423.GA17163@castle.DHCP.thefacebook.com>

On 02/20, Roman Gushchin wrote:
>
> On Wed, Feb 20, 2019 at 03:42:02PM +0100, Oleg Nesterov wrote:
> > On 02/19, Roman Gushchin wrote:
> > >
> > > @@ -2363,7 +2419,8 @@ bool get_signal(struct ksignal *ksig)
> > >  	 * we should notify the parent, prepare_signal(SIGCONT) encodes
> > >  	 * the CLD_ si_code into SIGNAL_CLD_MASK bits.
> > >  	 */
> > > -	if (unlikely(signal->flags & SIGNAL_CLD_MASK)) {
> > > +	if (unlikely(signal->flags & SIGNAL_CLD_MASK) &
> > > +	    !(current->jobctl & JOBCTL_TRAP_FREEZE)) {
> >
> > Hmm, why?
>
> If a process is going from the stopped to the frozen state, it looks like
> it's better to delay parent's notification up to the moment when it will
> actually run.

Perhaps I missed something but I do not understand why it is really better,
at least why it deserves this (small but still) complication...

OK, if nothing else, suppose that SIGCONT races with cgroup_do_freeze(true).
With or without this change CLD_CONTINUED can be reported or not depending
on /dev/random, do we really care?

Oleg.


  reply	other threads:[~2019-02-21 16:44 UTC|newest]

Thread overview: 25+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-02-19 22:02 [PATCH v8 0/7] freezer for cgroup v2 Roman Gushchin
2019-02-19 22:02 ` [PATCH v8 1/7] cgroup: rename freezer.c into legacy_freezer.c Roman Gushchin
2019-02-19 22:02 ` [PATCH v8 2/7] cgroup: implement __cgroup_task_count() helper Roman Gushchin
2019-02-19 22:02 ` [PATCH v8 3/7] cgroup: protect cgroup->nr_(dying_)descendants by css_set_lock Roman Gushchin
2019-02-19 22:02 ` [PATCH v8 4/7] cgroup: cgroup v2 freezer Roman Gushchin
2019-02-20 14:42   ` Oleg Nesterov
2019-02-20 22:14     ` Roman Gushchin
2019-02-21 16:44       ` Oleg Nesterov [this message]
2019-02-19 22:02 ` [PATCH v8 5/7] kselftests: cgroup: don't fail on cg_kill_all() error in cg_destroy() Roman Gushchin
2019-02-19 22:02   ` Roman Gushchin
2019-02-19 22:02   ` guroan
2019-02-19 22:02 ` [PATCH v8 6/7] kselftests: cgroup: add freezer controller self-tests Roman Gushchin
2019-02-19 22:02   ` Roman Gushchin
2019-02-19 22:02   ` guroan
2019-02-19 22:02 ` [PATCH v8 7/7] cgroup: document cgroup v2 freezer interface Roman Gushchin
2019-02-20 14:37 ` [PATCH v8 0/7] freezer for cgroup v2 Oleg Nesterov
2019-02-20 22:00   ` Roman Gushchin
2019-02-21 16:29     ` Oleg Nesterov
2019-02-21 17:34       ` Tejun Heo
2019-02-22 16:34         ` Oleg Nesterov
2019-02-22 18:17           ` Tejun Heo
2019-02-25 15:57             ` Oleg Nesterov
2019-03-05 17:27               ` Tejun Heo
2019-02-21 22:43       ` Roman Gushchin
2019-02-22 17:04         ` Oleg Nesterov

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