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Commit 7a4e344c authored by Tejun Heo's avatar Tejun Heo
Browse files

workqueue: introduce workqueue_attrs 



Introduce struct workqueue_attrs which carries worker attributes -
currently the nice level and allowed cpumask along with helper
routines alloc_workqueue_attrs() and free_workqueue_attrs().

Each worker_pool now carries ->attrs describing the attributes of its
workers.  All functions dealing with cpumask and nice level of workers
are updated to follow worker_pool->attrs instead of determining them
from other characteristics of the worker_pool, and init_workqueues()
is updated to set worker_pool->attrs appropriately for all standard
pools.

Note that create_worker() is updated to always perform set_user_nice()
and use set_cpus_allowed_ptr() combined with manual assertion of
PF_THREAD_BOUND instead of kthread_bind().  This simplifies handling
random attributes without affecting the outcome.

This patch doesn't introduce any behavior changes.

v2: Missing cpumask_var_t definition caused build failure on some
    archs.  linux/cpumask.h included.

Signed-off-by: default avatarTejun Heo <tj@kernel.org>
Reported-by: default avatarkbuild test robot <fengguang.wu@intel.com>
Reviewed-by: default avatarLai Jiangshan <laijs@cn.fujitsu.com>
parent 4e1a1f9a

include/linux/workqueue.h

+13 −0
Original line number Diff line number Diff line
@@ -11,6 +11,7 @@ 
#include <linux/lockdep.h>

#include <linux/threads.h>

#include <linux/atomic.h>

#include <linux/cpumask.h>



struct workqueue_struct;
@@ -115,6 +116,15 @@ struct delayed_work { 
	int cpu;

};



/*

 * A struct for workqueue attributes.  This can be used to change

 * attributes of an unbound workqueue.

 */

struct workqueue_attrs {

	int			nice;		/* nice level */

	cpumask_var_t		cpumask;	/* allowed CPUs */

};



static inline struct delayed_work *to_delayed_work(struct work_struct *work)

{

	return container_of(work, struct delayed_work, work);
@@ -399,6 +409,9 @@ __alloc_workqueue_key(const char *fmt, unsigned int flags, int max_active, 


extern void destroy_workqueue(struct workqueue_struct *wq);



struct workqueue_attrs *alloc_workqueue_attrs(gfp_t gfp_mask);

void free_workqueue_attrs(struct workqueue_attrs *attrs);



extern bool queue_work_on(int cpu, struct workqueue_struct *wq,

			struct work_struct *work);

extern bool queue_work(struct workqueue_struct *wq, struct work_struct *work);

kernel/workqueue.c

+81 −22
Original line number Diff line number Diff line
@@ -148,6 +148,8 @@ struct worker_pool { 
	struct mutex		assoc_mutex;	/* protect POOL_DISASSOCIATED */

	struct ida		worker_ida;	/* L: for worker IDs */



	struct workqueue_attrs	*attrs;		/* I: worker attributes */



	/*

	 * The current concurrency level.  As it's likely to be accessed

	 * from other CPUs during try_to_wake_up(), put it in a separate
@@ -1566,14 +1568,13 @@ __acquires(&pool->lock) 
		 * against POOL_DISASSOCIATED.

		 */

		if (!(pool->flags & POOL_DISASSOCIATED))

			set_cpus_allowed_ptr(current, get_cpu_mask(pool->cpu));

			set_cpus_allowed_ptr(current, pool->attrs->cpumask);



		spin_lock_irq(&pool->lock);

		if (pool->flags & POOL_DISASSOCIATED)

			return false;

		if (task_cpu(current) == pool->cpu &&

		    cpumask_equal(&current->cpus_allowed,

				  get_cpu_mask(pool->cpu)))

		    cpumask_equal(&current->cpus_allowed, pool->attrs->cpumask))

			return true;

		spin_unlock_irq(&pool->lock);
@@ -1679,7 +1680,7 @@ static void rebind_workers(struct worker_pool *pool) 
		 * wq doesn't really matter but let's keep @worker->pool

		 * and @pwq->pool consistent for sanity.

		 */

		if (std_worker_pool_pri(worker->pool))

		if (worker->pool->attrs->nice < 0)

			wq = system_highpri_wq;

		else

			wq = system_wq;
@@ -1721,7 +1722,7 @@ static struct worker *alloc_worker(void) 
 */

static struct worker *create_worker(struct worker_pool *pool)

{

	const char *pri = std_worker_pool_pri(pool) ? "H" : "";

	const char *pri = pool->attrs->nice < 0  ? "H" : "";

	struct worker *worker = NULL;

	int id = -1;
@@ -1751,24 +1752,23 @@ static struct worker *create_worker(struct worker_pool *pool) 
	if (IS_ERR(worker->task))

		goto fail;



	if (std_worker_pool_pri(pool))

		set_user_nice(worker->task, HIGHPRI_NICE_LEVEL);

	set_user_nice(worker->task, pool->attrs->nice);

	set_cpus_allowed_ptr(worker->task, pool->attrs->cpumask);



	/*

	 * Determine CPU binding of the new worker depending on

	 * %POOL_DISASSOCIATED.  The caller is responsible for ensuring the

	 * flag remains stable across this function.  See the comments

	 * above the flag definition for details.

	 *

	 * As an unbound worker may later become a regular one if CPU comes

	 * online, make sure every worker has %PF_THREAD_BOUND set.

	 * %PF_THREAD_BOUND is used to prevent userland from meddling with

	 * cpumask of workqueue workers.  This is an abuse.  We need

	 * %PF_NO_SETAFFINITY.

	 */

	if (!(pool->flags & POOL_DISASSOCIATED)) {

		kthread_bind(worker->task, pool->cpu);

	} else {

	worker->task->flags |= PF_THREAD_BOUND;



	/*

	 * The caller is responsible for ensuring %POOL_DISASSOCIATED

	 * remains stable across this function.  See the comments above the

	 * flag definition for details.

	 */

	if (pool->flags & POOL_DISASSOCIATED)

		worker->flags |= WORKER_UNBOUND;

	}



	return worker;

fail:
@@ -3123,7 +3123,52 @@ int keventd_up(void) 
	return system_wq != NULL;

}



static void init_worker_pool(struct worker_pool *pool)

/**

 * free_workqueue_attrs - free a workqueue_attrs

 * @attrs: workqueue_attrs to free

 *

 * Undo alloc_workqueue_attrs().

 */

void free_workqueue_attrs(struct workqueue_attrs *attrs)

{

	if (attrs) {

		free_cpumask_var(attrs->cpumask);

		kfree(attrs);

	}

}



/**

 * alloc_workqueue_attrs - allocate a workqueue_attrs

 * @gfp_mask: allocation mask to use

 *

 * Allocate a new workqueue_attrs, initialize with default settings and

 * return it.  Returns NULL on failure.

 */

struct workqueue_attrs *alloc_workqueue_attrs(gfp_t gfp_mask)

{

	struct workqueue_attrs *attrs;



	attrs = kzalloc(sizeof(*attrs), gfp_mask);

	if (!attrs)

		goto fail;

	if (!alloc_cpumask_var(&attrs->cpumask, gfp_mask))

		goto fail;



	cpumask_setall(attrs->cpumask);

	return attrs;

fail:

	free_workqueue_attrs(attrs);

	return NULL;

}



/**

 * init_worker_pool - initialize a newly zalloc'd worker_pool

 * @pool: worker_pool to initialize

 *

 * Initiailize a newly zalloc'd @pool.  It also allocates @pool->attrs.

 * Returns 0 on success, -errno on failure.

 */

static int init_worker_pool(struct worker_pool *pool)

{

	spin_lock_init(&pool->lock);

	pool->flags |= POOL_DISASSOCIATED;
@@ -3141,6 +3186,11 @@ static void init_worker_pool(struct worker_pool *pool) 
	mutex_init(&pool->manager_arb);

	mutex_init(&pool->assoc_mutex);

	ida_init(&pool->worker_ida);



	pool->attrs = alloc_workqueue_attrs(GFP_KERNEL);

	if (!pool->attrs)

		return -ENOMEM;

	return 0;

}



static int alloc_and_link_pwqs(struct workqueue_struct *wq)
@@ -3792,7 +3842,8 @@ void thaw_workqueues(void) 


static int __init init_workqueues(void)

{

	int cpu;

	int std_nice[NR_STD_WORKER_POOLS] = { 0, HIGHPRI_NICE_LEVEL };

	int i, cpu;



	/* make sure we have enough bits for OFFQ pool ID */

	BUILD_BUG_ON((1LU << (BITS_PER_LONG - WORK_OFFQ_POOL_SHIFT)) <
@@ -3809,10 +3860,18 @@ static int __init init_workqueues(void) 
	for_each_wq_cpu(cpu) {

		struct worker_pool *pool;



		i = 0;

		for_each_std_worker_pool(pool, cpu) {

			init_worker_pool(pool);

			BUG_ON(init_worker_pool(pool));

			pool->cpu = cpu;



			if (cpu != WORK_CPU_UNBOUND)

				cpumask_copy(pool->attrs->cpumask, cpumask_of(cpu));

			else

				cpumask_setall(pool->attrs->cpumask);



			pool->attrs->nice = std_nice[i++];



			/* alloc pool ID */

			BUG_ON(worker_pool_assign_id(pool));

		}