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Message-Id: <1258692407-8985-16-git-send-email-tj@kernel.org>
Date: Fri, 20 Nov 2009 13:46:43 +0900
From: Tejun Heo <tj@...nel.org>
To: torvalds@...ux-foundation.org, awalls@...ix.net,
linux-kernel@...r.kernel.org, jeff@...zik.org, mingo@...e.hu,
akpm@...ux-foundation.org, jens.axboe@...cle.com,
rusty@...tcorp.com.au, cl@...ux-foundation.org,
dhowells@...hat.com, arjan@...ux.intel.com, avi@...hat.com,
peterz@...radead.org, johannes@...solutions.net
Cc: Tejun Heo <tj@...nel.org>
Subject: [PATCH 15/19] workqueue: kill cpu_populated_map
Single threaded workqueue is scheduled to be reimplemented in the near
future. Kill cpu_populated_map and make single threaded workqueues
behave more like multi threaded ones - all cwqs are initialized and
all workqueues are linked on the workqueues list. This will ease
further changes.
While at it, make get_cwq() always return the cwq for the specified
cpu, add target_cwq() for cases where single thread distinction is
necessary and drop all direct usage of per_cpu_ptr() on wq->cpu_wq.
Signed-off-by: Tejun Heo <tj@...nel.org>
---
kernel/workqueue.c | 135 +++++++++++++++++++--------------------------------
1 files changed, 50 insertions(+), 85 deletions(-)
diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index 5392939..a255f43 100644
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -191,15 +191,6 @@ static DEFINE_SPINLOCK(workqueue_lock);
static LIST_HEAD(workqueues);
static int singlethread_cpu __read_mostly;
-static const struct cpumask *cpu_singlethread_map __read_mostly;
-/*
- * _cpu_down() first removes CPU from cpu_online_map, then CPU_DEAD
- * flushes cwq->worklist. This means that flush_workqueue/wait_on_work
- * which comes in between can't use for_each_online_cpu(). We could
- * use cpu_possible_map, the cpumask below is more a documentation
- * than optimization.
- */
-static cpumask_var_t cpu_populated_map __read_mostly;
/* If it's single threaded, it isn't in the list of workqueues. */
static inline bool is_wq_single_threaded(struct workqueue_struct *wq)
@@ -207,18 +198,18 @@ static inline bool is_wq_single_threaded(struct workqueue_struct *wq)
return wq->flags & WQ_SINGLE_THREAD;
}
-static const struct cpumask *wq_cpu_map(struct workqueue_struct *wq)
+static struct cpu_workqueue_struct *get_cwq(unsigned int cpu,
+ struct workqueue_struct *wq)
{
- return is_wq_single_threaded(wq)
- ? cpu_singlethread_map : cpu_populated_map;
+ return per_cpu_ptr(wq->cpu_wq, cpu);
}
-static struct cpu_workqueue_struct *get_cwq(unsigned int cpu,
- struct workqueue_struct *wq)
+static struct cpu_workqueue_struct *target_cwq(unsigned int cpu,
+ struct workqueue_struct *wq)
{
if (unlikely(is_wq_single_threaded(wq)))
cpu = singlethread_cpu;
- return per_cpu_ptr(wq->cpu_wq, cpu);
+ return get_cwq(cpu, wq);
}
/*
@@ -274,7 +265,7 @@ static void insert_work(struct cpu_workqueue_struct *cwq,
static void __queue_work(unsigned int cpu, struct workqueue_struct *wq,
struct work_struct *work)
{
- struct cpu_workqueue_struct *cwq = get_cwq(cpu, wq);
+ struct cpu_workqueue_struct *cwq = target_cwq(cpu, wq);
unsigned long flags;
debug_work_activate(work);
@@ -378,7 +369,7 @@ int queue_delayed_work_on(int cpu, struct workqueue_struct *wq,
timer_stats_timer_set_start_info(&dwork->timer);
/* This stores cwq for the moment, for the timer_fn */
- set_wq_data(work, get_cwq(raw_smp_processor_id(), wq), 0);
+ set_wq_data(work, target_cwq(raw_smp_processor_id(), wq), 0);
timer->expires = jiffies + delay;
timer->data = (unsigned long)dwork;
timer->function = delayed_work_timer_fn;
@@ -569,14 +560,13 @@ static int flush_cpu_workqueue(struct cpu_workqueue_struct *cwq)
*/
void flush_workqueue(struct workqueue_struct *wq)
{
- const struct cpumask *cpu_map = wq_cpu_map(wq);
int cpu;
might_sleep();
lock_map_acquire(&wq->lockdep_map);
lock_map_release(&wq->lockdep_map);
- for_each_cpu(cpu, cpu_map)
- flush_cpu_workqueue(per_cpu_ptr(wq->cpu_wq, cpu));
+ for_each_possible_cpu(cpu)
+ flush_cpu_workqueue(get_cwq(cpu, wq));
}
EXPORT_SYMBOL_GPL(flush_workqueue);
@@ -694,7 +684,6 @@ static void wait_on_work(struct work_struct *work)
{
struct cpu_workqueue_struct *cwq;
struct workqueue_struct *wq;
- const struct cpumask *cpu_map;
int cpu;
might_sleep();
@@ -707,9 +696,8 @@ static void wait_on_work(struct work_struct *work)
return;
wq = cwq->wq;
- cpu_map = wq_cpu_map(wq);
- for_each_cpu(cpu, cpu_map)
+ for_each_possible_cpu(cpu)
wait_on_cpu_work(get_cwq(cpu, wq), work);
}
@@ -942,7 +930,7 @@ int current_is_keventd(void)
BUG_ON(!keventd_wq);
- cwq = per_cpu_ptr(keventd_wq->cpu_wq, cpu);
+ cwq = get_cwq(cpu, keventd_wq);
if (current == cwq->thread)
ret = 1;
@@ -950,19 +938,6 @@ int current_is_keventd(void)
}
-static struct cpu_workqueue_struct *
-init_cpu_workqueue(struct workqueue_struct *wq, int cpu)
-{
- struct cpu_workqueue_struct *cwq = per_cpu_ptr(wq->cpu_wq, cpu);
-
- cwq->wq = wq;
- spin_lock_init(&cwq->lock);
- INIT_LIST_HEAD(&cwq->worklist);
- init_waitqueue_head(&cwq->more_work);
-
- return cwq;
-}
-
static int create_workqueue_thread(struct cpu_workqueue_struct *cwq, int cpu)
{
struct workqueue_struct *wq = cwq->wq;
@@ -1001,8 +976,8 @@ struct workqueue_struct *__create_workqueue_key(const char *name,
struct lock_class_key *key,
const char *lock_name)
{
+ bool singlethread = flags & WQ_SINGLE_THREAD;
struct workqueue_struct *wq;
- struct cpu_workqueue_struct *cwq;
int err = 0, cpu;
wq = kzalloc(sizeof(*wq), GFP_KERNEL);
@@ -1018,36 +993,38 @@ struct workqueue_struct *__create_workqueue_key(const char *name,
lockdep_init_map(&wq->lockdep_map, lock_name, key, 0);
INIT_LIST_HEAD(&wq->list);
- if (flags & WQ_SINGLE_THREAD) {
- cwq = init_cpu_workqueue(wq, singlethread_cpu);
- err = create_workqueue_thread(cwq, singlethread_cpu);
- start_workqueue_thread(cwq, -1);
- } else {
- cpu_maps_update_begin();
- /*
- * We must place this wq on list even if the code below fails.
- * cpu_down(cpu) can remove cpu from cpu_populated_map before
- * destroy_workqueue() takes the lock, in that case we leak
- * cwq[cpu]->thread.
- */
- spin_lock(&workqueue_lock);
- list_add(&wq->list, &workqueues);
- spin_unlock(&workqueue_lock);
- /*
- * We must initialize cwqs for each possible cpu even if we
- * are going to call destroy_workqueue() finally. Otherwise
- * cpu_up() can hit the uninitialized cwq once we drop the
- * lock.
- */
- for_each_possible_cpu(cpu) {
- cwq = init_cpu_workqueue(wq, cpu);
- if (err || !cpu_online(cpu))
- continue;
- err = create_workqueue_thread(cwq, cpu);
- start_workqueue_thread(cwq, cpu);
- }
- cpu_maps_update_done();
+ cpu_maps_update_begin();
+ /*
+ * We must place this wq on list even if the code below fails.
+ * cpu_down(cpu) can remove cpu from cpu_populated_map before
+ * destroy_workqueue() takes the lock, in that case we leak
+ * cwq[cpu]->thread.
+ */
+ spin_lock(&workqueue_lock);
+ list_add(&wq->list, &workqueues);
+ spin_unlock(&workqueue_lock);
+ /*
+ * We must initialize cwqs for each possible cpu even if we
+ * are going to call destroy_workqueue() finally. Otherwise
+ * cpu_up() can hit the uninitialized cwq once we drop the
+ * lock.
+ */
+ for_each_possible_cpu(cpu) {
+ struct cpu_workqueue_struct *cwq = get_cwq(cpu, wq);
+
+ cwq->wq = wq;
+ spin_lock_init(&cwq->lock);
+ INIT_LIST_HEAD(&cwq->worklist);
+ init_waitqueue_head(&cwq->more_work);
+
+ if (err || !cpu_online(cpu))
+ continue;
+ if (singlethread && cpu != singlethread_cpu)
+ continue;
+ err = create_workqueue_thread(cwq, cpu);
+ start_workqueue_thread(cwq, singlethread ? -1 : cpu);
}
+ cpu_maps_update_done();
if (err) {
destroy_workqueue(wq);
@@ -1098,7 +1075,6 @@ static void cleanup_workqueue_thread(struct cpu_workqueue_struct *cwq)
*/
void destroy_workqueue(struct workqueue_struct *wq)
{
- const struct cpumask *cpu_map = wq_cpu_map(wq);
int cpu;
cpu_maps_update_begin();
@@ -1106,8 +1082,8 @@ void destroy_workqueue(struct workqueue_struct *wq)
list_del(&wq->list);
spin_unlock(&workqueue_lock);
- for_each_cpu(cpu, cpu_map)
- cleanup_workqueue_thread(per_cpu_ptr(wq->cpu_wq, cpu));
+ for_each_possible_cpu(cpu)
+ cleanup_workqueue_thread(get_cwq(cpu, wq));
cpu_maps_update_done();
free_percpu(wq->cpu_wq);
@@ -1126,13 +1102,12 @@ static int __devinit workqueue_cpu_callback(struct notifier_block *nfb,
action &= ~CPU_TASKS_FROZEN;
- switch (action) {
- case CPU_UP_PREPARE:
- cpumask_set_cpu(cpu, cpu_populated_map);
- }
undo:
list_for_each_entry(wq, &workqueues, list) {
- cwq = per_cpu_ptr(wq->cpu_wq, cpu);
+ if (is_wq_single_threaded(wq))
+ continue;
+
+ cwq = get_cwq(cpu, wq);
switch (action) {
case CPU_UP_PREPARE:
@@ -1156,12 +1131,6 @@ undo:
}
}
- switch (action) {
- case CPU_UP_CANCELED:
- case CPU_POST_DEAD:
- cpumask_clear_cpu(cpu, cpu_populated_map);
- }
-
return ret;
}
@@ -1223,11 +1192,7 @@ void __init init_workqueues(void)
BUILD_BUG_ON(__alignof__(struct cpu_workqueue_struct) <
__alignof__(unsigned long long));
- alloc_cpumask_var(&cpu_populated_map, GFP_KERNEL);
-
- cpumask_copy(cpu_populated_map, cpu_online_mask);
singlethread_cpu = cpumask_first(cpu_possible_mask);
- cpu_singlethread_map = cpumask_of(singlethread_cpu);
hotcpu_notifier(workqueue_cpu_callback, 0);
keventd_wq = create_workqueue("events");
BUG_ON(!keventd_wq);
--
1.6.4.2
--
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