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workqueue: add wokrqueue_struct->maydays list to replace mayday cpu iterators 

Similar to how pool_workqueue iteration used to be, raising and
servicing mayday requests is based on CPU numbers.  It's hairy because
cpumask_t may not be able to handle WORK_CPU_UNBOUND and cpumasks are
assumed to be always set on UP.  This is ugly and can't handle
multiple unbound pools to be added for unbound workqueues w/ custom
attributes.

Add workqueue_struct->maydays.  When a pool_workqueue needs rescuing,
it gets chained on the list through pool_workqueue->mayday_node and
rescuer_thread() consumes the list until it's empty.

This patch doesn't introduce any visible behavior changes.

Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Lai Jiangshan <laijs@cn.fujitsu.com>
This commit is contained in:
Tejun Heo 2013-03-12 11:29:59 -07:00
parent 24b8a84718
commit 493a1724fe
1 changed files with 28 additions and 49 deletions
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77
kernel/workqueue.c
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@ -170,6 +170,7 @@ struct pool_workqueue {
int max_active; /* L: max active works */
struct list_head delayed_works; /* L: delayed works */
struct list_head pwqs_node; /* I: node on wq->pwqs */
struct list_head mayday_node; /* W: node on wq->maydays */
} __aligned(1 << WORK_STRUCT_FLAG_BITS);
/*
@ -181,27 +182,6 @@ struct wq_flusher {
struct completion done; /* flush completion */
};
/*
* All cpumasks are assumed to be always set on UP and thus can't be
* used to determine whether there's something to be done.
*/
#ifdef CONFIG_SMP
typedef cpumask_var_t mayday_mask_t;
#define mayday_test_and_set_cpu(cpu, mask) \
cpumask_test_and_set_cpu((cpu), (mask))
#define mayday_clear_cpu(cpu, mask) cpumask_clear_cpu((cpu), (mask))
#define for_each_mayday_cpu(cpu, mask) for_each_cpu((cpu), (mask))
#define alloc_mayday_mask(maskp, gfp) zalloc_cpumask_var((maskp), (gfp))
#define free_mayday_mask(mask) free_cpumask_var((mask))
#else
typedef unsigned long mayday_mask_t;
#define mayday_test_and_set_cpu(cpu, mask) test_and_set_bit(0, &(mask))
#define mayday_clear_cpu(cpu, mask) clear_bit(0, &(mask))
#define for_each_mayday_cpu(cpu, mask) if ((cpu) = 0, (mask))
#define alloc_mayday_mask(maskp, gfp) true
#define free_mayday_mask(mask) do { } while (0)
#endif
/*
* The externally visible workqueue abstraction is an array of
* per-CPU workqueues:
@ -224,7 +204,7 @@ struct workqueue_struct {
struct list_head flusher_queue; /* F: flush waiters */
struct list_head flusher_overflow; /* F: flush overflow list */
mayday_mask_t mayday_mask; /* cpus requesting rescue */
struct list_head maydays; /* W: pwqs requesting rescue */
struct worker *rescuer; /* I: rescue worker */
int nr_drainers; /* W: drain in progress */
@ -1850,23 +1830,21 @@ static void idle_worker_timeout(unsigned long __pool)
spin_unlock_irq(&pool->lock);
}
static bool send_mayday(struct work_struct *work)
static void send_mayday(struct work_struct *work)
{
struct pool_workqueue *pwq = get_work_pwq(work);
struct workqueue_struct *wq = pwq->wq;
unsigned int cpu;
lockdep_assert_held(&workqueue_lock);
if (!(wq->flags & WQ_RESCUER))
return false;
return;
/* mayday mayday mayday */
cpu = pwq->pool->cpu;
/* WORK_CPU_UNBOUND can't be set in cpumask, use cpu 0 instead */
if (cpu == WORK_CPU_UNBOUND)
cpu = 0;
if (!mayday_test_and_set_cpu(cpu, wq->mayday_mask))
if (list_empty(&pwq->mayday_node)) {
list_add_tail(&pwq->mayday_node, &wq->maydays);
wake_up_process(wq->rescuer->task);
return true;
}
}
static void pool_mayday_timeout(unsigned long __pool)
@ -1874,7 +1852,8 @@ static void pool_mayday_timeout(unsigned long __pool)
struct worker_pool *pool = (void *)__pool;
struct work_struct *work;
spin_lock_irq(&pool->lock);
spin_lock_irq(&workqueue_lock); /* for wq->maydays */
spin_lock(&pool->lock);
if (need_to_create_worker(pool)) {
/*
@ -1887,7 +1866,8 @@ static void pool_mayday_timeout(unsigned long __pool)
send_mayday(work);
}
spin_unlock_irq(&pool->lock);
spin_unlock(&pool->lock);
spin_unlock_irq(&workqueue_lock);
mod_timer(&pool->mayday_timer, jiffies + MAYDAY_INTERVAL);
}
@ -2336,8 +2316,6 @@ static int rescuer_thread(void *__rescuer)
struct worker *rescuer = __rescuer;
struct workqueue_struct *wq = rescuer->rescue_wq;
struct list_head *scheduled = &rescuer->scheduled;
bool is_unbound = wq->flags & WQ_UNBOUND;
unsigned int cpu;
set_user_nice(current, RESCUER_NICE_LEVEL);
@ -2355,18 +2333,19 @@ repeat:
return 0;
}
/*
* See whether any cpu is asking for help. Unbounded
* workqueues use cpu 0 in mayday_mask for CPU_UNBOUND.
*/
for_each_mayday_cpu(cpu, wq->mayday_mask) {
unsigned int tcpu = is_unbound ? WORK_CPU_UNBOUND : cpu;
struct pool_workqueue *pwq = get_pwq(tcpu, wq);
/* see whether any pwq is asking for help */
spin_lock_irq(&workqueue_lock);
while (!list_empty(&wq->maydays)) {
struct pool_workqueue *pwq = list_first_entry(&wq->maydays,
struct pool_workqueue, mayday_node);
struct worker_pool *pool = pwq->pool;
struct work_struct *work, *n;
__set_current_state(TASK_RUNNING);
mayday_clear_cpu(cpu, wq->mayday_mask);
list_del_init(&pwq->mayday_node);
spin_unlock_irq(&workqueue_lock);
/* migrate to the target cpu if possible */
worker_maybe_bind_and_lock(pool);
@ -2392,9 +2371,12 @@ repeat:
wake_up_worker(pool);
rescuer->pool = NULL;
spin_unlock_irq(&pool->lock);
spin_unlock(&pool->lock);
spin_lock(&workqueue_lock);
}
spin_unlock_irq(&workqueue_lock);
/* rescuers should never participate in concurrency management */
WARN_ON_ONCE(!(rescuer->flags & WORKER_NOT_RUNNING));
schedule();
@ -3192,6 +3174,7 @@ struct workqueue_struct *__alloc_workqueue_key(const char *fmt,
INIT_LIST_HEAD(&wq->pwqs);
INIT_LIST_HEAD(&wq->flusher_queue);
INIT_LIST_HEAD(&wq->flusher_overflow);
INIT_LIST_HEAD(&wq->maydays);
lockdep_init_map(&wq->lockdep_map, lock_name, key, 0);
INIT_LIST_HEAD(&wq->list);
@ -3205,14 +3188,12 @@ struct workqueue_struct *__alloc_workqueue_key(const char *fmt,
pwq->flush_color = -1;
pwq->max_active = max_active;
INIT_LIST_HEAD(&pwq->delayed_works);
INIT_LIST_HEAD(&pwq->mayday_node);
}
if (flags & WQ_RESCUER) {
struct worker *rescuer;
if (!alloc_mayday_mask(&wq->mayday_mask, GFP_KERNEL))
goto err;
wq->rescuer = rescuer = alloc_worker();
if (!rescuer)
goto err;
@ -3246,7 +3227,6 @@ struct workqueue_struct *__alloc_workqueue_key(const char *fmt,
err:
if (wq) {
free_pwqs(wq);
free_mayday_mask(wq->mayday_mask);
kfree(wq->rescuer);
kfree(wq);
}
@ -3289,7 +3269,6 @@ void destroy_workqueue(struct workqueue_struct *wq)
if (wq->flags & WQ_RESCUER) {
kthread_stop(wq->rescuer->task);
free_mayday_mask(wq->mayday_mask);
kfree(wq->rescuer);
}