linux-kernel - Re: [PATCH 5/6] workqueue: Allow modifying low level unbound workqueue cpumask

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Message-ID: <CACvQF539m8BJj5FKifsRhezkCaOSN_tBv3wUrjhcNe6E0D3r6Q@mail.gmail.com>
Date:	Thu, 8 May 2014 21:22:51 +0800
From:	Lai Jiangshan <laijs@...fujitsu.com>
To:	Frederic Weisbecker <fweisbec@...il.com>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	Christoph Lameter <cl@...ux.com>,
	Kevin Hilman <khilman@...aro.org>,
	Mike Galbraith <bitbucket@...ine.de>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	Tejun Heo <tj@...nel.org>,
	Viresh Kumar <viresh.kumar@...aro.org>
Subject: Re: [PATCH 5/6] workqueue: Allow modifying low level unbound
 workqueue cpumask

On Thu, May 8, 2014 at 12:37 AM, Frederic Weisbecker <fweisbec@...il.com> wrote:
> Allow to modify the low-level unbound workqueues cpumask through
> sysfs. This is performed by traversing the entire workqueue list
> and calling apply_workqueue_attrs() on the unbound workqueues.
>
> Cc: Christoph Lameter <cl@...ux.com>
> Cc: Kevin Hilman <khilman@...aro.org>
> Cc: Lai Jiangshan <laijs@...fujitsu.com>
> Cc: Mike Galbraith <bitbucket@...ine.de>
> Cc: Paul E. McKenney <paulmck@...ux.vnet.ibm.com>
> Cc: Tejun Heo <tj@...nel.org>
> Cc: Viresh Kumar <viresh.kumar@...aro.org>
> Signed-off-by: Frederic Weisbecker <fweisbec@...il.com>
> ---
>  kernel/workqueue.c | 65 ++++++++++++++++++++++++++++++++++++++++++++++++++++--
>  1 file changed, 63 insertions(+), 2 deletions(-)
>
> diff --git a/kernel/workqueue.c b/kernel/workqueue.c
> index 2aa296d..5978cee 100644
> --- a/kernel/workqueue.c
> +++ b/kernel/workqueue.c
> @@ -293,7 +293,7 @@ static DEFINE_SPINLOCK(wq_mayday_lock);     /* protects wq->maydays list */
>  static LIST_HEAD(workqueues);          /* PL: list of all workqueues */
>  static bool workqueue_freezing;                /* PL: have wqs started freezing? */
>
> -static cpumask_var_t wq_unbound_cpumask;
> +static cpumask_var_t wq_unbound_cpumask; /* PL: low level cpumask for all unbound wqs */
>
>  /* the per-cpu worker pools */
>  static DEFINE_PER_CPU_SHARED_ALIGNED(struct worker_pool [NR_STD_WORKER_POOLS],
> @@ -4084,19 +4084,80 @@ static struct bus_type wq_subsys = {
>         .dev_groups                     = wq_sysfs_groups,
>  };
>
> +static int unbounds_cpumask_apply(cpumask_var_t cpumask)
> +{
> +       struct workqueue_struct *wq;
> +       int ret;
> +
> +       lockdep_assert_held(&wq_pool_mutex);
> +
> +       list_for_each_entry(wq, &workqueues, list) {
> +               struct workqueue_attrs *attrs;
> +
> +               if (!(wq->flags & WQ_UNBOUND))
> +                       continue;
> +
> +               attrs = wq_sysfs_prep_attrs(wq);
> +               if (!attrs)
> +                       return -ENOMEM;
> +
> +               ret = apply_workqueue_attrs_locked(wq, attrs, cpumask);
> +               free_workqueue_attrs(attrs);
> +               if (ret)
> +                       break;
> +       }
> +
> +       return 0;
> +}
> +
> +static ssize_t unbounds_cpumask_store(struct device *dev,
> +                                     struct device_attribute *attr,
> +                                     const char *buf, size_t count)
> +{
> +       cpumask_var_t cpumask;
> +       int ret = -EINVAL;
> +
> +       if (!zalloc_cpumask_var(&cpumask, GFP_KERNEL))
> +               return -ENOMEM;
> +
> +       ret = cpumask_parse(buf, cpumask);
> +       if (ret)
> +               goto out;


     cpumask_and(cpumask, cpumask, cpu_possible_mask);

> +
> +       get_online_cpus();
> +       if (cpumask_intersects(cpumask, cpu_online_mask)) {
> +               mutex_lock(&wq_pool_mutex);
> +               ret = unbounds_cpumask_apply(cpumask);
> +               if (ret < 0) {
> +                       /* Warn if rollback itself fails */
> +                       WARN_ON_ONCE(unbounds_cpumask_apply(wq_unbound_cpumask));
> +               } else {
> +                       cpumask_copy(wq_unbound_cpumask, cpumask);
> +               }
> +               mutex_unlock(&wq_pool_mutex);
> +       }
> +       put_online_cpus();
> +out:
> +       free_cpumask_var(cpumask);
> +       return ret ? ret : count;
> +}
> +
>  static ssize_t unbounds_cpumask_show(struct device *dev,
>                                      struct device_attribute *attr, char *buf)
>  {
>         int written;
>
> +       mutex_lock(&wq_pool_mutex);
>         written = cpumask_scnprintf(buf, PAGE_SIZE, wq_unbound_cpumask);
> +       mutex_unlock(&wq_pool_mutex);
> +
>         written += scnprintf(buf + written, PAGE_SIZE - written, "\n");
>
>         return written;
>  }
>
>  static struct device_attribute wq_sysfs_cpumask_attr =
> -       __ATTR(cpumask, 0444, unbounds_cpumask_show, NULL);
> +       __ATTR(cpumask, 0644, unbounds_cpumask_show, unbounds_cpumask_store);
>
>  static int __init wq_sysfs_init(void)
>  {
> --
> 1.8.3.1
>
> --
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