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async: use workqueue for worker pool
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Replace private worker pool with system_unbound_wq.

Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Arjan van de Ven <arjan@infradead.org>
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@htejun
htejun committed Jul 14, 2010
1 parent c7fc77f commit 083b804
Showing 1 changed file with 22 additions and 119 deletions.
141 changes: 22 additions & 119 deletions kernel/async.c
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Expand Up @@ -49,40 +49,33 @@ asynchronous and synchronous parts of the kernel.
*/

#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 <linux/slab.h>
#include <linux/workqueue.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;

Expand Down Expand Up @@ -117,27 +110,23 @@ static async_cookie_t lowest_in_progress(struct list_head *running)
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));
Expand All @@ -153,31 +142,25 @@ 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);
Expand All @@ -186,7 +169,7 @@ static async_cookie_t __async_schedule(async_func_ptr *ptr, void *data, struct l
* 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++;
Expand All @@ -196,6 +179,7 @@ static async_cookie_t __async_schedule(async_func_ptr *ptr, void *data, struct l
ptr(data, newcookie);
return newcookie;
}
INIT_WORK(&entry->work, async_run_entry_fn);
entry->func = ptr;
entry->data = data;
entry->running = running;
Expand All @@ -205,7 +189,10 @@ static async_cookie_t __async_schedule(async_func_ptr *ptr, void *data, struct l
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_unbound_wq, &entry->work);

return newcookie;
}

Expand Down Expand Up @@ -312,87 +299,3 @@ void async_synchronize_cookie(async_cookie_t cookie)
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);

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