lkml.org 
[lkml]   [2009]   [Aug]   [19]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
DateThu, 20 Aug 2009 10:39:12 +0800
FromLi Zefan <>
SubjectRe: [PATCH 7/8] Adds functionality to read/write lock CLONE_THREAD fork()ing per-threadgroup
Paul Menage wrote:
> From: Ben Blum <bblum@google.com>
>
>
> Adds functionality to read/write lock CLONE_THREAD fork()ing per-threadgroup
>
> This patch adds an rwsem that lives in a threadgroup's sighand_struct (next to
> the sighand's atomic count, to piggyback on its cacheline), and two functions
> in kernel/cgroup.c (for now) for easily+safely obtaining and releasing it. If
> another part of the kernel later wants to use such a locking mechanism, the
> CONFIG_CGROUPS ifdefs should be changed to a higher-up flag that CGROUPS and
> the other system would both depend on, and the lock/unlock functions could be
> moved to sched.c or so.
>
> Signed-off-by: Ben Blum <bblum@google.com>
> Signed-off-by: Paul Menage <menage@google.com>
>

Looks fine to me.

Acked-by: Li Zefan <lizf@cn.fujitsu.com>

...

> +struct sighand_struct *threadgroup_fork_lock(struct task_struct *tsk)
> +{
> + struct sighand_struct *sighand;
> + struct task_struct *p;
> +
> + /* tasklist lock protects sighand_struct's disappearance in exit(). */
> + read_lock(&tasklist_lock);
> + if (likely(tsk->sighand)) {
> + /* simple case - check the thread we were given first */
> + sighand = tsk->sighand;
> + } else {
> + sighand = NULL;
> + /*
> + * tsk is exiting; try to find another thread in the group
> + * whose sighand pointer is still alive.
> + */
> + rcu_read_lock();

since we are holding tasklist_lock, I think we don't need to
take rcu lock?

> + list_for_each_entry_rcu(p, &tsk->thread_group, thread_group) {
> + if (p->sighand) {
> + sighand = tsk->sighand;

s/tsk->sighand/p->sighand

> + break;
> + }
> + }
> + rcu_read_unlock();
> + }


\
 
 \ /
  Last update: 2009-08-20 04:43    [from the cache]
©2003-2010