workqueue: Create low-level unbound workqueues cpumask

Create a cpumask that limits the affinity of all unbound workqueues.
This cpumask is controlled through a file at the root of the workqueue
sysfs directory.

It works on a lower-level than the per WQ_SYSFS workqueues cpumask files
such that the effective cpumask applied for a given unbound workqueue is
the intersection of /sys/devices/virtual/workqueue/$WORKQUEUE/cpumask and
the new /sys/devices/virtual/workqueue/cpumask file.

This patch implements the basic infrastructure and the read interface.
wq_unbound_cpumask is initially set to cpu_possible_mask.

Cc: Christoph Lameter <cl@linux.com>
Cc: Kevin Hilman <khilman@linaro.org>
Cc: Lai Jiangshan <laijs@cn.fujitsu.com>
Cc: Mike Galbraith <bitbucket@online.de>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
Signed-off-by: Tejun Heo <tj@kernel.org>

diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index 26ff249240160b6fb79ee07a71691555ab91bb9a..9be75e2a4da6cb041d10d65701d780fd46a38e89 100644 (file)
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -299,6 +299,8 @@ static DEFINE_SPINLOCK(wq_mayday_lock);     /* protects wq->maydays list */
 static LIST_HEAD(workqueues);          /* PR: list of all workqueues */
 static bool workqueue_freezing;                /* PL: have wqs started freezing? */
 
+static cpumask_var_t wq_unbound_cpumask;
+
 /* the per-cpu worker pools */
 static DEFINE_PER_CPU_SHARED_ALIGNED(struct worker_pool [NR_STD_WORKER_POOLS],
                                     cpu_worker_pools);
@@ -3532,7 +3534,7 @@ apply_wqattrs_prepare(struct workqueue_struct *wq,
 
        /* make a copy of @attrs and sanitize it */
        copy_workqueue_attrs(new_attrs, attrs);
-       cpumask_and(new_attrs->cpumask, new_attrs->cpumask, cpu_possible_mask);
+       cpumask_and(new_attrs->cpumask, new_attrs->cpumask, wq_unbound_cpumask);
 
        /*
         * We may create multiple pwqs with differing cpumasks.  Make a
@@ -4945,9 +4947,29 @@ static struct bus_type wq_subsys = {
        .dev_groups                     = wq_sysfs_groups,
 };
 
+static ssize_t wq_unbound_cpumask_show(struct device *dev,
+               struct device_attribute *attr, char *buf)
+{
+       int written;
+
+       written = scnprintf(buf, PAGE_SIZE, "%*pb\n",
+                           cpumask_pr_args(wq_unbound_cpumask));
+
+       return written;
+}
+
+static struct device_attribute wq_sysfs_cpumask_attr =
+       __ATTR(cpumask, 0444, wq_unbound_cpumask_show, NULL);
+
 static int __init wq_sysfs_init(void)
 {
-       return subsys_virtual_register(&wq_subsys, NULL);
+       int err;
+
+       err = subsys_virtual_register(&wq_subsys, NULL);
+       if (err)
+               return err;
+
+       return device_create_file(wq_subsys.dev_root, &wq_sysfs_cpumask_attr);
 }
 core_initcall(wq_sysfs_init);
 
@@ -5095,6 +5117,9 @@ static int __init init_workqueues(void)
 
        WARN_ON(__alignof__(struct pool_workqueue) < __alignof__(long long));
 
+       BUG_ON(!alloc_cpumask_var(&wq_unbound_cpumask, GFP_KERNEL));
+       cpumask_copy(wq_unbound_cpumask, cpu_possible_mask);
+
        pwq_cache = KMEM_CACHE(pool_workqueue, SLAB_PANIC);
 
        cpu_notifier(workqueue_cpu_up_callback, CPU_PRI_WORKQUEUE_UP);