From: Alan Stern <stern@rowland.harvard.edu>
To: Tejun Heo <tj@kernel.org>
Cc: "Colin Cross" <ccross@android.com>,
"Linux PM list" <linux-pm@vger.kernel.org>,
lkml <linux-kernel@vger.kernel.org>,
"Rafael J. Wysocki" <rjw@sisk.pl>,
"Arve Hjønnevåg" <arve@android.com>,
"Oleg Nesterov" <oleg@redhat.com>,
"Len Brown" <len.brown@intel.com>, "Pavel Machek" <pavel@ucw.cz>,
"Jeff Layton" <jlayton@redhat.com>,
"Mandeep Baines" <msb@chromium.org>
Subject: Re: [PATCH v2 03/10] freezer: add new freezable helpers using freezer_do_not_count()
Date: Fri, 3 May 2013 10:18:17 -0400 (EDT) [thread overview]
Message-ID: <Pine.LNX.4.44L0.1305031017030.1513-100000@iolanthe.rowland.org> (raw)
In-Reply-To: <20130503040934.GA16968@mtj.dyndns.org>
On Thu, 2 May 2013, Tejun Heo wrote:
> Combined with the locking problems, I was planning to update the
> freezer such that the frozen state is implemented as a form of jobctl
> stop, so that things like ptrace / kill -9 could work on them and we
> also have the clear definition of the frozen state rather than the
> current "it may get stuck somewhere in the kernel".
>
> But that conflicts with what you're doing here which seems pretty
> useful, so, to satisfy both goals, when somebody needs to put a
> pseudo-frozen task into the actual frozen jobctl stop, those spots
> which are currently using try_to_stop() would have to return an error,
> most likely -EINTR with TIF_SIGPENDING set, and the control should
> return towards userland so that signal handling path can be invoked.
> ie. It should be possible to steer the tasks which are considered
> frozen but not in the frozen jobctl stop into the jobctl stop without
> any side effect. To do that, those spots basically have to be pretty
> close to the userland boundary where it can easily leave the kernel
> with -EINTR and AFAICS all the spots that you converted are like that
> (which I think is natural). While not holding any locks doesn't
> guarantee that, I think there'd be a fairly high correlation at least
> and it'd be able to drive people towards finding out what's going on.
Don't forget about freezable kernel threads. They never cross the
kernel/user boundary.
Alan Stern
next prev parent reply other threads:[~2013-05-03 14:18 UTC|newest]
Thread overview: 36+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-05-02 1:34 [PATCH v2 00/10] optimize freezing tasks by reducing task wakeups Colin Cross
2013-05-02 1:34 ` [PATCH v2 01/10] freezer: shorten freezer sleep time using exponential backoff Colin Cross
2013-05-02 23:20 ` Tejun Heo
2013-05-02 1:35 ` [PATCH v2 02/10] freezer: skip waking up tasks with PF_FREEZER_SKIP set Colin Cross
2013-05-02 23:24 ` Tejun Heo
2013-05-03 9:24 ` Pavel Machek
2013-05-02 1:35 ` [PATCH v2 03/10] freezer: add new freezable helpers using freezer_do_not_count() Colin Cross
2013-05-02 23:55 ` Tejun Heo
2013-05-03 0:03 ` Tejun Heo
2013-05-03 2:16 ` Colin Cross
2013-05-03 2:41 ` Colin Cross
2013-05-03 4:09 ` Tejun Heo
2013-05-03 4:12 ` Tejun Heo
2013-05-03 4:17 ` Colin Cross
2013-05-03 4:20 ` Tejun Heo
2013-05-03 14:18 ` Alan Stern [this message]
2013-05-03 16:54 ` Tejun Heo
2013-05-02 1:35 ` [PATCH v2 04/10] binder: use freezable blocking calls Colin Cross
2013-05-02 1:35 ` [PATCH v2 05/10] epoll: use freezable blocking call Colin Cross
2013-05-02 1:35 ` [PATCH v2 06/10] select: " Colin Cross
2013-05-02 1:35 ` [PATCH v2 07/10] futex: " Colin Cross
2013-05-02 19:45 ` Thomas Gleixner
2013-05-03 3:12 ` Darren Hart
2013-06-25 21:15 ` [tip:core/locking] futex: Use " tip-bot for Colin Cross
2013-05-02 1:35 ` [PATCH v2 08/10] nanosleep: use " Colin Cross
2013-05-02 19:46 ` Thomas Gleixner
2013-05-02 1:35 ` [PATCH v2 09/10] sigtimedwait: " Colin Cross
2013-05-02 1:35 ` [PATCH v2 10/10] af_unix: use freezable blocking calls in read Colin Cross
2013-05-03 0:08 ` Tejun Heo
2013-05-04 19:19 ` Rafael J. Wysocki
2013-05-04 20:39 ` Tejun Heo
2013-05-04 22:23 ` Colin Cross
2013-05-05 11:23 ` Rafael J. Wysocki
2013-05-02 21:06 ` [PATCH v2 00/10] optimize freezing tasks by reducing task wakeups Rafael J. Wysocki
2013-05-03 0:10 ` Tejun Heo
2013-05-03 11:43 ` Rafael J. Wysocki
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