[PATCH] async: use workqueue for worker pool

Tejun Heo
2010-01-22T10:54:33Z

Replace private worker pool with system_long_wq.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Arjan van de Ven <arjan@infradead.org>
---
Alright, here's the patch to just convert the worker pool. Boots fine
here.

Thanks.

kernel/async.c | 140 ++++++++-------------------------------------------------
1 file changed, 21 insertions(+), 119 deletions(-)

Index: work/kernel/async.c
===================================================================
--- work.orig/kernel/async.c
+++ work/kernel/async.c
@@ -49,39 +49,31 @@ asynchronous and synchronous parts of th
*/

#include <linux/async.h>
-#include <linux/bug.h>
#include <linux/module.h>
#include <linux/wait.h>
#include <linux/sched.h>
-#include <linux/init.h>
-#include <linux/kthread.h>
-#include <linux/delay.h>
#include <asm/atomic.h>

static async_cookie_t next_cookie = 1;

-#define MAX_THREADS 256
#define MAX_WORK 32768

static LIST_HEAD(async_pending);
static LIST_HEAD(async_running);
static DEFINE_SPINLOCK(async_lock);

-static int async_enabled = 0;
-
struct async_entry {
- struct list_head list;
- async_cookie_t cookie;
- async_func_ptr *func;
- void *data;
- struct list_head *running;
+ struct list_head list;
+ struct work_struct work;
+ async_cookie_t cookie;
+ async_func_ptr *func;
+ void *data;
+ struct list_head *running;
};

static DECLARE_WAIT_QUEUE_HEAD(async_done);
-static DECLARE_WAIT_QUEUE_HEAD(async_new);

static atomic_t entry_count;
-static atomic_t thread_count;

extern int initcall_debug;

@@ -116,27 +108,23 @@ static async_cookie_t lowest_in_progres
spin_unlock_irqrestore(&async_lock, flags);
return ret;
}
+
/*
* pick the first pending entry and run it
*/
-static void run_one_entry(void)
+static void async_run_entry_fn(struct work_struct *work)
{
+ struct async_entry *entry =
+ container_of(work, struct async_entry, work);
unsigned long flags;
- struct async_entry *entry;
ktime_t calltime, delta, rettime;

- /* 1) pick one task from the pending queue */
-
+ /* 1) move self to the running queue */
spin_lock_irqsave(&async_lock, flags);
- if (list_empty(&async_pending))
- goto out;
- entry = list_first_entry(&async_pending, struct async_entry, list);
-
- /* 2) move it to the running queue */
list_move_tail(&entry->list, entry->running);
spin_unlock_irqrestore(&async_lock, flags);

- /* 3) run it (and print duration)*/
+ /* 2) run (and print duration) */
if (initcall_debug && system_state == SYSTEM_BOOTING) {
printk("calling %lli_%pF @ %i\n", (long long)entry->cookie,
entry->func, task_pid_nr(current));
@@ -152,31 +140,25 @@ static void run_one_entry(void)
(long long)ktime_to_ns(delta) >> 10);
}

- /* 4) remove it from the running queue */
+ /* 3) remove self from the running queue */
spin_lock_irqsave(&async_lock, flags);
list_del(&entry->list);

- /* 5) free the entry */
+ /* 4) free the entry */
kfree(entry);
atomic_dec(&entry_count);

spin_unlock_irqrestore(&async_lock, flags);

- /* 6) wake up any waiters. */
+ /* 5) wake up any waiters */
wake_up(&async_done);
- return;
-
-out:
- spin_unlock_irqrestore(&async_lock, flags);
}

-
static async_cookie_t __async_schedule(async_func_ptr *ptr, void *data, struct list_head *running)
{
struct async_entry *entry;
unsigned long flags;
async_cookie_t newcookie;
-

/* allow irq-off callers */
entry = kzalloc(sizeof(struct async_entry), GFP_ATOMIC);
@@ -185,7 +167,7 @@ static async_cookie_t __async_schedule(a
* If we're out of memory or if there's too much work
* pending already, we execute synchronously.
*/
- if (!async_enabled || !entry || atomic_read(&entry_count) > MAX_WORK) {
+ if (!entry || atomic_read(&entry_count) > MAX_WORK) {
kfree(entry);
spin_lock_irqsave(&async_lock, flags);
newcookie = next_cookie++;
@@ -195,6 +177,7 @@ static async_cookie_t __async_schedule(a
ptr(data, newcookie);
return newcookie;
}
+ INIT_WORK(&entry->work, async_run_entry_fn);
entry->func = ptr;
entry->data = data;
entry->running = running;
@@ -204,7 +187,10 @@ static async_cookie_t __async_schedule(a
list_add_tail(&entry->list, &async_pending);
atomic_inc(&entry_count);
spin_unlock_irqrestore(&async_lock, flags);
- wake_up(&async_new);
+
+ /* schedule for execution */
+ queue_work(system_long_wq, &entry->work);
+
return newcookie;
}

@@ -311,87 +297,3 @@ void async_synchronize_cookie(async_cook
async_synchronize_cookie_domain(cookie, &async_running);
}
EXPORT_SYMBOL_GPL(async_synchronize_cookie);
-
-
-static int async_thread(void *unused)
-{
- DECLARE_WAITQUEUE(wq, current);
- add_wait_queue(&async_new, &wq);
-
- while (!kthread_should_stop()) {
- int ret = HZ;
- set_current_state(TASK_INTERRUPTIBLE);
- /*
- * check the list head without lock.. false positives
- * are dealt with inside run_one_entry() while holding
- * the lock.
- */
- rmb();
- if (!list_empty(&async_pending))
- run_one_entry();
- else
- ret = schedule_timeout(HZ);
-
- if (ret == 0) {
- /*
- * we timed out, this means we as thread are redundant.
- * we sign off and die, but we to avoid any races there
- * is a last-straw check to see if work snuck in.
- */
- atomic_dec(&thread_count);
- wmb(); /* manager must see our departure first */
- if (list_empty(&async_pending))
- break;
- /*
- * woops work came in between us timing out and us
- * signing off; we need to stay alive and keep working.
- */
- atomic_inc(&thread_count);
- }
- }
- remove_wait_queue(&async_new, &wq);
-
- return 0;
-}
-
-static int async_manager_thread(void *unused)
-{
- DECLARE_WAITQUEUE(wq, current);
- add_wait_queue(&async_new, &wq);
-
- while (!kthread_should_stop()) {
- int tc, ec;
-
- set_current_state(TASK_INTERRUPTIBLE);
-
- tc = atomic_read(&thread_count);
- rmb();
- ec = atomic_read(&entry_count);
-
- while (tc < ec && tc < MAX_THREADS) {
- if (IS_ERR(kthread_run(async_thread, NULL, "async/%i",
- tc))) {
- msleep(100);
- continue;
- }
- atomic_inc(&thread_count);
- tc++;
- }
-
- schedule();
- }
- remove_wait_queue(&async_new, &wq);
-
- return 0;
-}
-
-static int __init async_init(void)
-{
- async_enabled =
- !IS_ERR(kthread_run(async_manager_thread, NULL, "async/mgr"));
-
- WARN_ON(!async_enabled);
- return 0;
-}
-
-core_initcall(async_init);