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Date: Fri, 9 Aug 2013 13:49:44 -0400
From: Chris Metcalf <cmetcalf@...era.com>
To: <linux-kernel@...r.kernel.org>, <linux-mm@...ck.org>,
Tejun Heo <tj@...nel.org>,
Thomas Gleixner <tglx@...utronix.de>,
Frederic Weisbecker <fweisbec@...il.com>,
Cody P Schafer <cody@...ux.vnet.ibm.com>
Subject: [PATCH v6 1/2] workqueue: add new schedule_on_cpu_mask() API
This primitive allows scheduling work to run on a particular set of
cpus described by a "struct cpumask". This can be useful, for example,
if you have a per-cpu variable that requires code execution only if the
per-cpu variable has a certain value (for example, is a non-empty list).
Acked-by: Tejun Heo <tj@...nel.org>
Signed-off-by: Chris Metcalf <cmetcalf@...era.com>
---
v6: add Tejun's Acked-by, and add missing get/put_cpu_online to
lru_add_drain_all().
v5: provide validity checking on the cpumask for schedule_on_cpu_mask.
By providing an all-or-nothing EINVAL check, we impose the requirement
that the calling code actually know clearly what it's trying to do.
(Note: no change to the mm/swap.c commit)
v4: don't lose possible -ENOMEM in schedule_on_each_cpu()
(Note: no change to the mm/swap.c commit)
v3: split commit into two, one for workqueue and one for mm, though both
should probably be taken through -mm.
include/linux/workqueue.h | 3 +++
kernel/workqueue.c | 51 ++++++++++++++++++++++++++++++++++++++---------
2 files changed, 45 insertions(+), 9 deletions(-)
diff --git a/include/linux/workqueue.h b/include/linux/workqueue.h
index a0ed78a..71a3fe7 100644
--- a/include/linux/workqueue.h
+++ b/include/linux/workqueue.h
@@ -13,6 +13,8 @@
#include <linux/atomic.h>
#include <linux/cpumask.h>
+struct cpumask;
+
struct workqueue_struct;
struct work_struct;
@@ -470,6 +472,7 @@ extern void flush_workqueue(struct workqueue_struct *wq);
extern void drain_workqueue(struct workqueue_struct *wq);
extern void flush_scheduled_work(void);
+extern int schedule_on_cpu_mask(work_func_t func, const struct cpumask *mask);
extern int schedule_on_each_cpu(work_func_t func);
int execute_in_process_context(work_func_t fn, struct execute_work *);
diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index f02c4a4..63d504a 100644
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -292,6 +292,9 @@ 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? */
+/* set of cpus that are valid for per-cpu workqueue scheduling */
+static struct cpumask wq_valid_cpus;
+
/* the per-cpu worker pools */
static DEFINE_PER_CPU_SHARED_ALIGNED(struct worker_pool [NR_STD_WORKER_POOLS],
cpu_worker_pools);
@@ -2962,43 +2965,66 @@ bool cancel_delayed_work_sync(struct delayed_work *dwork)
EXPORT_SYMBOL(cancel_delayed_work_sync);
/**
- * schedule_on_each_cpu - execute a function synchronously on each online CPU
+ * schedule_on_cpu_mask - execute a function synchronously on each listed CPU
* @func: the function to call
+ * @mask: the cpumask to invoke the function on
*
- * schedule_on_each_cpu() executes @func on each online CPU using the
+ * schedule_on_cpu_mask() executes @func on each listed CPU using the
* system workqueue and blocks until all CPUs have completed.
- * schedule_on_each_cpu() is very slow.
+ * schedule_on_cpu_mask() is very slow. You may only specify CPUs
+ * that are online or have previously been online; specifying an
+ * invalid CPU mask will return -EINVAL without scheduling any work.
*
* RETURNS:
* 0 on success, -errno on failure.
*/
-int schedule_on_each_cpu(work_func_t func)
+int schedule_on_cpu_mask(work_func_t func, const struct cpumask *mask)
{
int cpu;
struct work_struct __percpu *works;
+ if (!cpumask_subset(mask, &wq_valid_cpus))
+ return -EINVAL;
+
works = alloc_percpu(struct work_struct);
if (!works)
return -ENOMEM;
- get_online_cpus();
-
- for_each_online_cpu(cpu) {
+ for_each_cpu(cpu, mask) {
struct work_struct *work = per_cpu_ptr(works, cpu);
INIT_WORK(work, func);
schedule_work_on(cpu, work);
}
- for_each_online_cpu(cpu)
+ for_each_cpu(cpu, mask)
flush_work(per_cpu_ptr(works, cpu));
- put_online_cpus();
free_percpu(works);
return 0;
}
/**
+ * schedule_on_each_cpu - execute a function synchronously on each online CPU
+ * @func: the function to call
+ *
+ * schedule_on_each_cpu() executes @func on each online CPU using the
+ * system workqueue and blocks until all CPUs have completed.
+ * schedule_on_each_cpu() is very slow.
+ *
+ * RETURNS:
+ * 0 on success, -errno on failure.
+ */
+int schedule_on_each_cpu(work_func_t func)
+{
+ int ret;
+ get_online_cpus();
+ ret = schedule_on_cpu_mask(func, cpu_online_mask);
+ put_online_cpus();
+ return ret;
+}
+
+/**
* flush_scheduled_work - ensure that any scheduled work has run to completion.
*
* Forces execution of the kernel-global workqueue and blocks until its
@@ -4687,6 +4713,9 @@ static int __cpuinit workqueue_cpu_up_callback(struct notifier_block *nfb,
list_for_each_entry(wq, &workqueues, list)
wq_update_unbound_numa(wq, cpu, true);
+ /* track the set of cpus that have ever been online */
+ cpumask_set_cpu(cpu, &wq_valid_cpus);
+
mutex_unlock(&wq_pool_mutex);
break;
}
@@ -5011,6 +5040,10 @@ static int __init init_workqueues(void)
!system_unbound_wq || !system_freezable_wq ||
!system_power_efficient_wq ||
!system_freezable_power_efficient_wq);
+
+ /* mark startup cpu as valid */
+ cpumask_set_cpu(smp_processor_id(), &wq_valid_cpus);
+
return 0;
}
early_initcall(init_workqueues);
--
1.8.3.1
--
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