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cpu-hotplug: replace per-subsystem mutexes with get_online_cpus()

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This patch converts the known per-subsystem mutexes to get_online_cpus
put_online_cpus. It also eliminates the CPU_LOCK_ACQUIRE and
CPU_LOCK_RELEASE hotplug notification events.

Signed-off-by: Gautham  R Shenoy <ego@in.ibm.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Gautham R Shenoy
2008-01-25 21:08:02 +01:00
committed by Ingo Molnar
parent 86ef5c9a8e
commit 95402b3829
5 changed files with 36 additions and 50 deletions
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35
kernel/workqueue.c
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@@ -67,9 +67,8 @@ struct workqueue_struct {
#endif
};
/* All the per-cpu workqueues on the system, for hotplug cpu to add/remove
threads to each one as cpus come/go. */
static DEFINE_MUTEX(workqueue_mutex);
/* Serializes the accesses to the list of workqueues. */
static DEFINE_SPINLOCK(workqueue_lock);
static LIST_HEAD(workqueues);
static int singlethread_cpu __read_mostly;
@@ -592,8 +591,6 @@ EXPORT_SYMBOL(schedule_delayed_work_on);
* Returns zero on success.
* Returns -ve errno on failure.
*
* Appears to be racy against CPU hotplug.
*
* schedule_on_each_cpu() is very slow.
*/
int schedule_on_each_cpu(work_func_t func)
@@ -605,7 +602,7 @@ int schedule_on_each_cpu(work_func_t func)
if (!works)
return -ENOMEM;
preempt_disable(); /* CPU hotplug */
get_online_cpus();
for_each_online_cpu(cpu) {
struct work_struct *work = per_cpu_ptr(works, cpu);
@@ -613,8 +610,8 @@ int schedule_on_each_cpu(work_func_t func)
set_bit(WORK_STRUCT_PENDING, work_data_bits(work));
__queue_work(per_cpu_ptr(keventd_wq->cpu_wq, cpu), work);
}
preempt_enable();
flush_workqueue(keventd_wq);
put_online_cpus();
free_percpu(works);
return 0;
}
@@ -750,8 +747,10 @@ struct workqueue_struct *__create_workqueue_key(const char *name,
err = create_workqueue_thread(cwq, singlethread_cpu);
start_workqueue_thread(cwq, -1);
} else {
mutex_lock(&workqueue_mutex);
get_online_cpus();
spin_lock(&workqueue_lock);
list_add(&wq->list, &workqueues);
spin_unlock(&workqueue_lock);
for_each_possible_cpu(cpu) {
cwq = init_cpu_workqueue(wq, cpu);
@@ -760,7 +759,7 @@ struct workqueue_struct *__create_workqueue_key(const char *name,
err = create_workqueue_thread(cwq, cpu);
start_workqueue_thread(cwq, cpu);
}
mutex_unlock(&workqueue_mutex);
put_online_cpus();
}
if (err) {
@@ -775,7 +774,7 @@ static void cleanup_workqueue_thread(struct cpu_workqueue_struct *cwq, int cpu)
{
/*
* Our caller is either destroy_workqueue() or CPU_DEAD,
* workqueue_mutex protects cwq->thread
* get_online_cpus() protects cwq->thread.
*/
if (cwq->thread == NULL)
return;
@@ -810,9 +809,11 @@ void destroy_workqueue(struct workqueue_struct *wq)
struct cpu_workqueue_struct *cwq;
int cpu;
mutex_lock(&workqueue_mutex);
get_online_cpus();
spin_lock(&workqueue_lock);
list_del(&wq->list);
mutex_unlock(&workqueue_mutex);
spin_unlock(&workqueue_lock);
put_online_cpus();
for_each_cpu_mask(cpu, *cpu_map) {
cwq = per_cpu_ptr(wq->cpu_wq, cpu);
@@ -835,13 +836,6 @@ static int __devinit workqueue_cpu_callback(struct notifier_block *nfb,
action &= ~CPU_TASKS_FROZEN;
switch (action) {
case CPU_LOCK_ACQUIRE:
mutex_lock(&workqueue_mutex);
return NOTIFY_OK;
case CPU_LOCK_RELEASE:
mutex_unlock(&workqueue_mutex);
return NOTIFY_OK;
case CPU_UP_PREPARE:
cpu_set(cpu, cpu_populated_map);
@@ -854,7 +848,8 @@ static int __devinit workqueue_cpu_callback(struct notifier_block *nfb,
case CPU_UP_PREPARE:
if (!create_workqueue_thread(cwq, cpu))
break;
printk(KERN_ERR "workqueue for %i failed\n", cpu);
printk(KERN_ERR "workqueue [%s] for %i failed\n",
wq->name, cpu);
return NOTIFY_BAD;
case CPU_ONLINE: