linux-kernel - Re: [PATCH 19/26] cgroups: Convert cgroups release_list_lock to raw

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Date:	Mon, 11 Jan 2010 17:11:04 -0500 (EST)
From:	John Kacur <jkacur@...hat.com>
To:	Paul Menage <menage@...gle.com>
Cc:	Thomas Gleixner <tglx@...utronix.de>,
	lkml <linux-kernel@...r.kernel.org>, Ingo Molnar <mingo@...e.hu>,
	Clark Williams <williams@...hat.com>
Subject: Re: [PATCH 19/26] cgroups: Convert cgroups release_list_lock to
  raw_spinlock


----- "Paul Menage" <menage@...gle.com> wrote:

> Does this patch take the lock out of the scope of lockdep? Or is
> raw_spinlock still high-level enough to support lockdep?

lockdep should work as before - in fact everything should work as before.
This is pretty much a no-op until preempt-rt changes are pushed upstream.
> 
> Paul
> 
> On Mon, Jan 11, 2010 at 1:26 PM, John Kacur <jkacur@...hat.com>
> wrote:
> > Convert locks which cannot sleep in preempt-rt to raw_spinlocks
> >
> > See also 58814bae5de64d5291b813ea0a52192e4fa714ad
> >
> > Signed-off-by: John Kacur <jkacur@...hat.com>
> > ---
> >  kernel/cgroup.c |   18 +++++++++---------
> >  1 files changed, 9 insertions(+), 9 deletions(-)
> >
> > diff --git a/kernel/cgroup.c b/kernel/cgroup.c
> > index 0249f4b..32a80b2 100644
> > --- a/kernel/cgroup.c
> > +++ b/kernel/cgroup.c
> > @@ -204,7 +204,7 @@ list_for_each_entry(_root, &roots, root_list)
> >  /* the list of cgroups eligible for automatic release. Protected
> by
> >  * release_list_lock */
> >  static LIST_HEAD(release_list);
> > -static DEFINE_SPINLOCK(release_list_lock);
> > +static DEFINE_RAW_SPINLOCK(release_list_lock);
> >  static void cgroup_release_agent(struct work_struct *work);
> >  static DECLARE_WORK(release_agent_work, cgroup_release_agent);
> >  static void check_for_release(struct cgroup *cgrp);
> > @@ -3151,11 +3151,11 @@ again:
> >        finish_wait(&cgroup_rmdir_waitq, &wait);
> >        clear_bit(CGRP_WAIT_ON_RMDIR, &cgrp->flags);
> >
> > -       spin_lock(&release_list_lock);
> > +       raw_spin_lock(&release_list_lock);
> >        set_bit(CGRP_REMOVED, &cgrp->flags);
> >        if (!list_empty(&cgrp->release_list))
> >                list_del(&cgrp->release_list);
> > -       spin_unlock(&release_list_lock);
> > +       raw_spin_unlock(&release_list_lock);
> >
> >        cgroup_lock_hierarchy(cgrp->root);
> >        /* delete this cgroup from parent->children */
> > @@ -3691,13 +3691,13 @@ static void check_for_release(struct cgroup
> *cgrp)
> >                 * already queued for a userspace notification,
> queue
> >                 * it now */
> >                int need_schedule_work = 0;
> > -               spin_lock(&release_list_lock);
> > +               raw_spin_lock(&release_list_lock);
> >                if (!cgroup_is_removed(cgrp) &&
> >                    list_empty(&cgrp->release_list)) {
> >                        list_add(&cgrp->release_list,
> &release_list);
> >                        need_schedule_work = 1;
> >                }
> > -               spin_unlock(&release_list_lock);
> > +               raw_spin_unlock(&release_list_lock);
> >                if (need_schedule_work)
> >                        schedule_work(&release_agent_work);
> >        }
> > @@ -3747,7 +3747,7 @@ static void cgroup_release_agent(struct
> work_struct *work)
> >  {
> >        BUG_ON(work != &release_agent_work);
> >        mutex_lock(&cgroup_mutex);
> > -       spin_lock(&release_list_lock);
> > +       raw_spin_lock(&release_list_lock);
> >        while (!list_empty(&release_list)) {
> >                char *argv[3], *envp[3];
> >                int i;
> > @@ -3756,7 +3756,7 @@ static void cgroup_release_agent(struct
> work_struct *work)
> >                                                    struct cgroup,
> >                                                    release_list);
> >                list_del_init(&cgrp->release_list);
> > -               spin_unlock(&release_list_lock);
> > +               raw_spin_unlock(&release_list_lock);
> >                pathbuf = kmalloc(PAGE_SIZE, GFP_KERNEL);
> >                if (!pathbuf)
> >                        goto continue_free;
> > @@ -3786,9 +3786,9 @@ static void cgroup_release_agent(struct
> work_struct *work)
> >  continue_free:
> >                kfree(pathbuf);
> >                kfree(agentbuf);
> > -               spin_lock(&release_list_lock);
> > +               raw_spin_lock(&release_list_lock);
> >        }
> > -       spin_unlock(&release_list_lock);
> > +       raw_spin_unlock(&release_list_lock);
> >        mutex_unlock(&cgroup_mutex);
> >  }
> >
> > --
> > 1.6.5.2
> >
> > --
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