[PATCH 7/8] Clean up workqueue.c with respect to the freezer based cpu-hotplug
From: Gautham R Shenoy
Date: Mon Apr 02 2007 - 01:43:59 EST
Clean up workqueue.c from the perspective of freezer-based cpu-hotplug.
This patch
o Removes cpu_populated_map as cpu_online_map is safe to use.
o removes cwq_should_stop and uses kthread_should_stop instead.
o Reintroduces take_over_work from the worker_thread of a downed
cpu. This means that all non-singlethreaded workqueues *have* to
be frozen to avoid any races.
Signed-off-by: Gautham R Shenoy <ego@xxxxxxxxxx>
Signed-off-by: Srivatsa Vaddagiri <vatsa@xxxxxxxxxx>
Cc: Oleg Nesterov <oleg@xxxxxxxxxx>
--
kernel/workqueue.c | 118 ++++++++++++++++++++++-------------------------------
1 files changed, 50 insertions(+), 68 deletions(-)
Index: linux-2.6.21-rc4/kernel/workqueue.c
===================================================================
--- linux-2.6.21-rc4.orig/kernel/workqueue.c
+++ linux-2.6.21-rc4/kernel/workqueue.c
@@ -47,10 +47,6 @@ struct cpu_workqueue_struct {
struct workqueue_struct *wq;
struct task_struct *thread;
- int status;
- #define CWQ_RUNNING 0
- #define CWQ_SHOULD_STOP 1
- #define CWQ_STOPPED 2
int run_depth; /* Detect run_workqueue() recursion depth */
} ____cacheline_aligned;
@@ -75,7 +71,6 @@ static LIST_HEAD(workqueues);
static int singlethread_cpu __read_mostly;
static cpumask_t cpu_singlethread_map __read_mostly;
/* optimization, we could use cpu_possible_map */
-static cpumask_t cpu_populated_map __read_mostly;
/* If it's single threaded, it isn't in the list of workqueues. */
static inline int is_single_threaded(struct workqueue_struct *wq)
@@ -86,7 +81,7 @@ static inline int is_single_threaded(str
static const cpumask_t *wq_cpu_map(struct workqueue_struct *wq)
{
return is_single_threaded(wq)
- ? &cpu_singlethread_map : &cpu_populated_map;
+ ? &cpu_singlethread_map : &cpu_online_map;
}
static
@@ -270,32 +265,16 @@ static void run_workqueue(struct cpu_wor
spin_unlock_irq(&cwq->lock);
}
-/*
- * NOTE: the caller must not touch *cwq if this func returns true
- */
-static int cwq_should_stop(struct cpu_workqueue_struct *cwq)
-{
- int should_stop = cwq->status;
-
- if (unlikely(should_stop == CWQ_SHOULD_STOP)) {
- spin_lock_irq(&cwq->lock);
- should_stop = cwq->status && list_empty(&cwq->worklist);
- if (should_stop)
- cwq->status= CWQ_STOPPED;
- spin_unlock_irq(&cwq->lock);
- }
-
- return should_stop;
-}
static int worker_thread(void *__cwq)
{
struct cpu_workqueue_struct *cwq = __cwq;
+ int bind_cpu;
DEFINE_WAIT(wait);
struct k_sigaction sa;
freezer_exempt(cwq->wq->freeze_exempt_events);
-
+ bind_cpu = smp_processor_id();
/*
* We inherited MPOL_INTERLEAVE from the booting kernel.
* Set MPOL_DEFAULT to insure node local allocations.
@@ -308,20 +287,28 @@ static int worker_thread(void *__cwq)
siginitset(&sa.sa.sa_mask, sigmask(SIGCHLD));
do_sigaction(SIGCHLD, &sa, (struct k_sigaction *)0);
- for (;;) {
+ while (!kthread_should_stop()) {
try_to_freeze();
-
+
+ if (cpu_is_offline(bind_cpu) && !is_single_threaded(cwq->wq))
+ goto wait_to_die;
+
prepare_to_wait(&cwq->more_work, &wait, TASK_INTERRUPTIBLE);
- if (cwq->status == CWQ_RUNNING && list_empty(&cwq->worklist))
+ if (list_empty(&cwq->worklist))
schedule();
finish_wait(&cwq->more_work, &wait);
- if (cwq_should_stop(cwq))
- break;
-
run_workqueue(cwq);
}
+wait_to_die:
+ set_current_state(TASK_INTERRUPTIBLE);
+ while(!kthread_should_stop()) {
+ schedule();
+ set_current_state(TASK_INTERRUPTIBLE);
+ }
+ __set_current_state(TASK_RUNNING);
+
return 0;
}
@@ -386,11 +373,10 @@ static void flush_cpu_workqueue(struct c
*/
void fastcall flush_workqueue(struct workqueue_struct *wq)
{
- const cpumask_t *cpu_map = wq_cpu_map(wq);
int cpu;
might_sleep();
- for_each_cpu_mask(cpu, *cpu_map)
+ for_each_online_cpu(cpu)
flush_cpu_workqueue(per_cpu_ptr(wq->cpu_wq, cpu));
}
EXPORT_SYMBOL_GPL(flush_workqueue);
@@ -644,13 +630,6 @@ static int create_workqueue_thread(struc
return PTR_ERR(p);
cwq->thread = p;
- cwq->status = CWQ_RUNNING;
- if (!is_single_threaded(wq))
- kthread_bind(p, cpu);
-
- if (is_single_threaded(wq) || cpu_online(cpu))
- wake_up_process(p);
-
return 0;
}
@@ -680,15 +659,21 @@ static struct workqueue_struct *__create
if (singlethread) {
cwq = init_cpu_workqueue(wq, singlethread_cpu);
err = create_workqueue_thread(cwq, singlethread_cpu);
+ wake_up_process(cwq->thread);
} else {
mutex_lock(&workqueue_mutex);
list_add(&wq->list, &workqueues);
- for_each_possible_cpu(cpu) {
+ for_each_online_cpu(cpu) {
cwq = init_cpu_workqueue(wq, cpu);
if (err || !cpu_online(cpu))
continue;
err = create_workqueue_thread(cwq, cpu);
+ if (err)
+ continue;
+
+ kthread_bind(cwq->thread, cpu);
+ wake_up_process(cwq->thread);
}
mutex_unlock(&workqueue_mutex);
}
@@ -721,30 +706,11 @@ EXPORT_SYMBOL_GPL(create_singlethread_wo
static void cleanup_workqueue_thread(struct cpu_workqueue_struct *cwq, int cpu)
{
- struct wq_barrier barr;
- int alive = 0;
- spin_lock_irq(&cwq->lock);
if (cwq->thread != NULL) {
- insert_wq_barrier(cwq, &barr, 1);
- cwq->status = CWQ_SHOULD_STOP;
- alive = 1;
- }
- spin_unlock_irq(&cwq->lock);
-
- if (alive) {
thaw_process(cwq->thread);
- wait_for_completion(&barr.done);
-
- while (unlikely(cwq->status != CWQ_STOPPED))
- cpu_relax();
- /*
- * Wait until cwq->thread unlocks cwq->lock,
- * it won't touch *cwq after that.
- */
- smp_rmb();
+ kthread_stop(cwq->thread);
cwq->thread = NULL;
- spin_unlock_wait(&cwq->lock);
}
}
@@ -756,15 +722,16 @@ static void cleanup_workqueue_thread(str
*/
void destroy_workqueue(struct workqueue_struct *wq)
{
- const cpumask_t *cpu_map = wq_cpu_map(wq);
struct cpu_workqueue_struct *cwq;
int cpu;
+ flush_workqueue(wq);
+
mutex_lock(&workqueue_mutex);
list_del(&wq->list);
mutex_unlock(&workqueue_mutex);
- for_each_cpu_mask(cpu, *cpu_map) {
+ for_each_online_cpu(cpu) {
cwq = per_cpu_ptr(wq->cpu_wq, cpu);
cleanup_workqueue_thread(cwq, cpu);
}
@@ -774,6 +741,25 @@ void destroy_workqueue(struct workqueue_
}
EXPORT_SYMBOL_GPL(destroy_workqueue);
+/*Take the work from this (downed) CPU. */
+static void take_over_work(struct workqueue_struct *wq, unsigned int cpu)
+{
+ struct cpu_workqueue_struct *cwq = per_cpu_ptr(wq->cpu_wq, cpu);
+ struct list_head list;
+ struct work_struct *work;
+
+ spin_lock_irq(&cwq->lock);
+ list_replace_init(&cwq->worklist, &list);
+
+ while (!list_empty(&list)) {
+ work = list_entry(list.next,struct work_struct,entry);
+ list_del(&work->entry);
+ __queue_work(per_cpu_ptr(wq->cpu_wq, smp_processor_id()), work);
+ }
+ spin_unlock_irq(&cwq->lock);
+}
+
+
static int __devinit workqueue_cpu_callback(struct notifier_block *nfb,
unsigned long action,
void *hcpu)
@@ -782,11 +768,6 @@ static int __devinit workqueue_cpu_callb
struct cpu_workqueue_struct *cwq;
struct workqueue_struct *wq;
- switch (action) {
- case CPU_UP_PREPARE:
- cpu_set(cpu, cpu_populated_map);
- }
-
mutex_lock(&workqueue_mutex);
list_for_each_entry(wq, &workqueues, list) {
cwq = per_cpu_ptr(wq->cpu_wq, cpu);
@@ -799,6 +780,7 @@ static int __devinit workqueue_cpu_callb
return NOTIFY_BAD;
case CPU_ONLINE:
+ kthread_bind(cwq->thread, cpu);
wake_up_process(cwq->thread);
break;
@@ -806,6 +788,7 @@ static int __devinit workqueue_cpu_callb
if (cwq->thread)
wake_up_process(cwq->thread);
case CPU_DEAD:
+ take_over_work(wq, cpu);
cleanup_workqueue_thread(cwq, cpu);
break;
}
@@ -817,7 +800,6 @@ static int __devinit workqueue_cpu_callb
void __init init_workqueues(void)
{
- cpu_populated_map = cpu_online_map;
singlethread_cpu = first_cpu(cpu_possible_map);
cpu_singlethread_map = cpumask_of_cpu(singlethread_cpu);
hotcpu_notifier(workqueue_cpu_callback, 0);
--
Gautham R Shenoy
Linux Technology Center
IBM India.
"Freedom comes with a price tag of responsibility, which is still a bargain,
because Freedom is priceless!"
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/