From: Paul Menage <menage@google.com>
To: Oleg Nesterov <oleg@redhat.com>
Cc: akpm@linux-foundation.org, linux-kernel@vger.kernel.org,
bblum@google.com, ebiederm@xmission.com, lizf@cn.fujitsu.com,
matthltc@us.ibm.com
Subject: Re: + cgroups-add-functionality-to-read-write-lock-clone_thread-forking-pe r-threadgroup.patch added to -mm tree
Date: Sat, 22 Aug 2009 06:28:04 -0700 [thread overview]
Message-ID: <6599ad830908220628o7dc99cf1i5908d3e95deb31e5@mail.gmail.com> (raw)
In-Reply-To: <20090822130952.GA4240@redhat.com>
On Sat, Aug 22, 2009 at 6:09 AM, Oleg Nesterov<oleg@redhat.com> wrote:
>
>
> And why do we need sighand->threadgroup_fork_lock ? I gueess, to protect
> against clone(CLONE_THREAD).
Right - we want to be able to atomically move all the threads in the
thread group into a new cgroup, without leaving any behind if we
happen to race with a clone(CLONE_THREAD).
Putting the lock in the sighand structure seemed like an appropriate
place since it's involved in existing clone() synchronization.
>
> threadgroup_fork_lock() bumps P->sighand->count. If P exec, it will
> notice sighand->count != 1 and switch to another ->sighand.
So maybe we should also down_read(threadgroup_fork_lock) in the exec
path? That would prevent a child thread from execing and taking over
the group leadership, so it would remain safe to iterate over the
group leader's thread list.
Paul
next prev parent reply other threads:[~2009-08-22 13:28 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <200908202114.n7KLEN5H026646@imap1.linux-foundation.org>
2009-08-21 10:26 ` + cgroups-add-functionality-to-read-write-lock-clone_thread-forking-pe r-threadgroup.patch added to -mm tree Oleg Nesterov
2009-08-21 10:45 ` Oleg Nesterov
2009-08-21 23:37 ` Paul Menage
2009-08-22 13:09 ` Oleg Nesterov
2009-08-22 13:28 ` Paul Menage [this message]
2010-01-03 19:06 ` Ben Blum
2010-01-03 19:07 ` [RFC] [PATCH 1/2] cgroups: read-write lock CLONE_THREAD forking per threadgroup Ben Blum
2010-01-05 18:53 ` Oleg Nesterov
2010-01-17 20:48 ` Ben Blum
2010-03-22 10:22 ` Oleg Nesterov
2010-03-22 23:57 ` Paul Menage
2010-01-03 19:09 ` [RFC] [PATCH 2/2] cgroups: make procs file writable Ben Blum
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