From: Oleg Nesterov <oleg@redhat.com>
To: Tejun Heo <tj@kernel.org>
Cc: rjw@sisk.pl, linux-kernel@vger.kernel.org, lizefan@huawei.com,
containers@lists.linux-foundation.org, cgroups@vger.kernel.org,
stable@vger.kernel.org
Subject: Re: [PATCH 1/7] cgroup: cgroup_subsys->fork() should be called after the task is added to css_set
Date: Thu, 25 Oct 2012 19:42:33 +0200 [thread overview]
Message-ID: <20121025174233.GC7650@redhat.com> (raw)
In-Reply-To: <20121024190458.GB12182@atj.dyndns.org>
On 10/24, Tejun Heo wrote:
>
> Hello,
>
> On Tue, Oct 23, 2012 at 05:51:28PM +0200, Oleg Nesterov wrote:
> > Yes, yes. But in this case (I mean, for uprobes) "threadgroup" in the name
> > is misleading. It should be called unconditially without any argument.
> >
> > Please see
> >
> > [PATCH 1/2] brw_mutex: big read-write mutex
> > http://marc.info/?l=linux-kernel&m=135032816223715
>
> Ooh... that's something completely different.
>
> > [PATCH 2/2] uprobes: Use brw_mutex to fix register/unregister vs dup_mmap() race
> > http://marc.info/?l=linux-kernel&m=135032817823720
> >
> > for details, but in short 2/2 needs this giant lock to block dup_mmap()
> > system-wide, while cgroup (currently) only needs threadgroup lock if
> > CLONE_THREAD (ignoring do_exit) and per-task.
> >
> > So please forget, I no longer think it makes sense to use the same
> > thing for uprobes and cgroups.
>
> It is quite tempting to reduce hot path overhead and penalize cgroup
> migration ops more tho. Write-locking brw_mutex on migration might
> not be too bad. Why did you change your mind?
Well, mostly because I do not think 1/2 will be ever applied ;)
Since we already have (to my surprise!) percpu_rw_semaphore, I do
not think I can add another similar lock.
Perhaps uprobes can use percpu_rw_semaphore, but I am not sure...
Oleg.
next prev parent reply other threads:[~2012-10-25 17:41 UTC|newest]
Thread overview: 63+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-10-16 22:28 [PATCHSET cgroup/for-3.8] cgroup_freezer: allow migration regardless of freezer state and update locking Tejun Heo
2012-10-16 22:28 ` [PATCH 1/7] cgroup: cgroup_subsys->fork() should be called after the task is added to css_set Tejun Heo
2012-10-17 8:28 ` Li Zefan
2012-10-18 1:25 ` Li Zefan
2012-10-21 19:11 ` Oleg Nesterov
2012-10-21 19:22 ` Tejun Heo
2012-10-22 18:04 ` Oleg Nesterov
2012-10-22 21:16 ` Tejun Heo
2012-10-23 15:51 ` Oleg Nesterov
2012-10-24 19:04 ` Tejun Heo
2012-10-25 17:42 ` Oleg Nesterov [this message]
2012-12-20 5:25 ` Herton Ronaldo Krzesinski
2012-12-28 21:22 ` [PATCH] cgroup: remove unused dummy cgroup_fork_callbacks() Tejun Heo
2012-10-16 22:28 ` [PATCH 2/7] freezer: add missing mb's to freezer_count() and freezer_should_skip() Tejun Heo
2012-10-22 17:44 ` Oleg Nesterov
2012-10-22 21:13 ` Tejun Heo
2012-10-23 15:39 ` Oleg Nesterov
2012-10-24 18:57 ` Tejun Heo
2012-10-25 16:39 ` [PATCH 0/1] (Was: freezer: add missing mb's to freezer_count() and freezer_should_skip()) Oleg Nesterov
2012-10-25 16:39 ` [PATCH 1/1] freezer: change ptrace_stop/do_signal_stop to use freezable_schedule() Oleg Nesterov
2012-10-25 17:18 ` Tejun Heo
2012-10-25 17:34 ` Oleg Nesterov
2012-10-25 17:36 ` Tejun Heo
2012-10-26 17:45 ` [PATCH v2 0/1] " Oleg Nesterov
2012-10-26 17:46 ` [PATCH v2 1/1] " Oleg Nesterov
2012-10-26 17:52 ` Tejun Heo
2012-10-26 18:01 ` Oleg Nesterov
2012-10-26 21:14 ` Rafael J. Wysocki
2012-10-26 21:29 ` Rafael J. Wysocki
2012-10-26 21:29 ` Tejun Heo
2012-10-28 0:16 ` Rafael J. Wysocki
2012-10-27 22:22 ` Ben Hutchings
2012-10-28 13:45 ` Oleg Nesterov
2012-10-16 22:28 ` [PATCH 3/7] cgroup_freezer: make it official that writes to freezer.state don't fail Tejun Heo
2012-10-16 22:28 ` [PATCH 4/7] cgroup_freezer: don't stall transition to FROZEN for PF_NOFREEZE or PF_FREEZER_SKIP tasks Tejun Heo
2012-10-22 18:34 ` Oleg Nesterov
2012-10-22 21:18 ` Tejun Heo
2012-10-23 15:55 ` Oleg Nesterov
2012-10-24 19:06 ` Tejun Heo
2012-10-25 17:12 ` [PATCH 0/1] (Was: cgroup_freezer: don't stall transition to FROZEN for PF_NOFREEZE or PF_FREEZER_SKIP tasks) Oleg Nesterov
2012-10-25 17:12 ` [PATCH 1/1] freezer: exec should clear PF_NOFREEZE along with PF_KTHREAD Oleg Nesterov
2012-10-25 17:20 ` Tejun Heo
2012-10-25 17:37 ` Oleg Nesterov
2012-10-25 17:37 ` Tejun Heo
2012-10-25 20:13 ` Rafael J. Wysocki
2012-10-16 22:28 ` [PATCH 5/7] cgroup_freezer: allow moving tasks in and out of a frozen cgroup Tejun Heo
2012-10-22 19:25 ` Oleg Nesterov
2012-10-22 21:25 ` Tejun Heo
2012-10-23 16:14 ` Oleg Nesterov
2012-10-16 22:28 ` [PATCH 6/7] cgroup_freezer: prepare update_if_frozen() for locking change Tejun Heo
2012-10-16 22:28 ` [PATCH 7/7] cgroup_freezer: don't use cgroup_lock_live_group() Tejun Heo
2012-10-17 19:16 ` [PATCHSET cgroup/for-3.8] cgroup_freezer: allow migration regardless of freezer state and update locking Matt Helsley
2012-10-18 21:14 ` Tejun Heo
2012-10-18 22:21 ` Matt Helsley
2012-10-18 22:35 ` Tejun Heo
2012-10-18 23:47 ` Matt Helsley
2012-10-19 0:01 ` Tejun Heo
2012-10-19 1:29 ` Matt Helsley
2012-10-19 20:02 ` Tejun Heo
2012-10-19 16:54 ` Rafael J. Wysocki
2012-10-19 20:04 ` Tejun Heo
2012-10-21 19:18 ` Oleg Nesterov
2012-10-21 19:24 ` Tejun Heo
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