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Commit 7c3eed5c authored by Tejun Heo's avatar Tejun Heo
Browse files

workqueue: record pool ID instead of CPU in work->data when off-queue 



Currently, when a work item is off-queue, work->data records the CPU
it was last on, which is used to locate the last executing instance
for non-reentrance, flushing, etc.

We're in the process of removing global_cwq and making worker_pool the
top level abstraction.  This patch makes work->data point to the pool
it was last associated with instead of CPU.

After the previous WORK_OFFQ_POOL_CPU and worker_poo->id additions,
the conversion is fairly straight-forward.  WORK_OFFQ constants and
functions are modified to record and read back pool ID instead.
worker_pool_by_id() is added to allow looking up pool from ID.
get_work_pool() replaces get_work_gcwq(), which is reimplemented using
get_work_pool().  get_work_pool_id() replaces work_cpu().

This patch shouldn't introduce any observable behavior changes.

Signed-off-by: default avatarTejun Heo <tj@kernel.org>
Reviewed-by: default avatarLai Jiangshan <laijs@cn.fujitsu.com>
parent 9daf9e67

include/linux/workqueue.h

+9 −9
Original line number Diff line number Diff line
@@ -75,19 +75,19 @@ enum { 


	/*

	 * When a work item is off queue, its high bits point to the last

	 * cpu it was on.  Cap at 31 bits and use the highest number to

	 * indicate that no cpu is associated.

	 * pool it was on.  Cap at 31 bits and use the highest number to

	 * indicate that no pool is associated.

	 */

	WORK_OFFQ_FLAG_BITS	= 1,

	WORK_OFFQ_CPU_SHIFT	= WORK_OFFQ_FLAG_BASE + WORK_OFFQ_FLAG_BITS,

	WORK_OFFQ_LEFT		= BITS_PER_LONG - WORK_OFFQ_CPU_SHIFT,

	WORK_OFFQ_CPU_BITS	= WORK_OFFQ_LEFT <= 31 ? WORK_OFFQ_LEFT : 31,

	WORK_OFFQ_CPU_NONE	= (1LU << WORK_OFFQ_CPU_BITS) - 1,

	WORK_OFFQ_POOL_SHIFT	= WORK_OFFQ_FLAG_BASE + WORK_OFFQ_FLAG_BITS,

	WORK_OFFQ_LEFT		= BITS_PER_LONG - WORK_OFFQ_POOL_SHIFT,

	WORK_OFFQ_POOL_BITS	= WORK_OFFQ_LEFT <= 31 ? WORK_OFFQ_LEFT : 31,

	WORK_OFFQ_POOL_NONE	= (1LU << WORK_OFFQ_POOL_BITS) - 1,



	/* convenience constants */

	WORK_STRUCT_FLAG_MASK	= (1UL << WORK_STRUCT_FLAG_BITS) - 1,

	WORK_STRUCT_WQ_DATA_MASK = ~WORK_STRUCT_FLAG_MASK,

	WORK_STRUCT_NO_CPU	= (unsigned long)WORK_OFFQ_CPU_NONE << WORK_OFFQ_CPU_SHIFT,

	WORK_STRUCT_NO_POOL	= (unsigned long)WORK_OFFQ_POOL_NONE << WORK_OFFQ_POOL_SHIFT,



	/* bit mask for work_busy() return values */

	WORK_BUSY_PENDING	= 1 << 0,
@@ -103,9 +103,9 @@ struct work_struct { 
#endif

};



#define WORK_DATA_INIT()	ATOMIC_LONG_INIT(WORK_STRUCT_NO_CPU)

#define WORK_DATA_INIT()	ATOMIC_LONG_INIT(WORK_STRUCT_NO_POOL)

#define WORK_DATA_STATIC_INIT()	\

	ATOMIC_LONG_INIT(WORK_STRUCT_NO_CPU | WORK_STRUCT_STATIC)

	ATOMIC_LONG_INIT(WORK_STRUCT_NO_POOL | WORK_STRUCT_STATIC)



struct delayed_work {

	struct work_struct work;

kernel/workqueue.c

+67 −44
Original line number Diff line number Diff line
@@ -451,7 +451,6 @@ static DEFINE_MUTEX(worker_pool_idr_mutex); 
static DEFINE_IDR(worker_pool_idr);



static int worker_thread(void *__worker);

static unsigned int work_cpu(struct work_struct *work);



static int std_worker_pool_pri(struct worker_pool *pool)

{
@@ -479,6 +478,15 @@ static int worker_pool_assign_id(struct worker_pool *pool) 
	return ret;

}



/*

 * Lookup worker_pool by id.  The idr currently is built during boot and

 * never modified.  Don't worry about locking for now.

 */

static struct worker_pool *worker_pool_by_id(int pool_id)

{

	return idr_find(&worker_pool_idr, pool_id);

}



static atomic_t *get_pool_nr_running(struct worker_pool *pool)

{

	int cpu = pool->gcwq->cpu;
@@ -520,17 +528,17 @@ static int work_next_color(int color) 
/*

 * While queued, %WORK_STRUCT_CWQ is set and non flag bits of a work's data

 * contain the pointer to the queued cwq.  Once execution starts, the flag

 * is cleared and the high bits contain OFFQ flags and CPU number.

 * is cleared and the high bits contain OFFQ flags and pool ID.

 *

 * set_work_cwq(), set_work_cpu_and_clear_pending(), mark_work_canceling()

 * and clear_work_data() can be used to set the cwq, cpu or clear

 * set_work_cwq(), set_work_pool_and_clear_pending(), mark_work_canceling()

 * and clear_work_data() can be used to set the cwq, pool or clear

 * work->data.  These functions should only be called while the work is

 * owned - ie. while the PENDING bit is set.

 *

 * get_work_[g]cwq() can be used to obtain the gcwq or cwq corresponding to

 * a work.  gcwq is available once the work has been queued anywhere after

 * initialization until it is sync canceled.  cwq is available only while

 * the work item is queued.

 * get_work_pool() and get_work_cwq() can be used to obtain the pool or cwq

 * corresponding to a work.  Pool is available once the work has been

 * queued anywhere after initialization until it is sync canceled.  cwq is

 * available only while the work item is queued.

 *

 * %WORK_OFFQ_CANCELING is used to mark a work item which is being

 * canceled.  While being canceled, a work item may have its PENDING set
@@ -552,8 +560,8 @@ static void set_work_cwq(struct work_struct *work, 
		      WORK_STRUCT_PENDING | WORK_STRUCT_CWQ | extra_flags);

}



static void set_work_cpu_and_clear_pending(struct work_struct *work,

					   unsigned int cpu)

static void set_work_pool_and_clear_pending(struct work_struct *work,

					    int pool_id)

{

	/*

	 * The following wmb is paired with the implied mb in
@@ -562,13 +570,13 @@ static void set_work_cpu_and_clear_pending(struct work_struct *work, 
	 * owner.

	 */

	smp_wmb();

	set_work_data(work, (unsigned long)cpu << WORK_OFFQ_CPU_SHIFT, 0);

	set_work_data(work, (unsigned long)pool_id << WORK_OFFQ_POOL_SHIFT, 0);

}



static void clear_work_data(struct work_struct *work)

{

	smp_wmb();	/* see set_work_cpu_and_clear_pending() */

	set_work_data(work, WORK_STRUCT_NO_CPU, 0);

	smp_wmb();	/* see set_work_pool_and_clear_pending() */

	set_work_data(work, WORK_STRUCT_NO_POOL, 0);

}



static struct cpu_workqueue_struct *get_work_cwq(struct work_struct *work)
@@ -581,30 +589,58 @@ static struct cpu_workqueue_struct *get_work_cwq(struct work_struct *work) 
		return NULL;

}



static struct global_cwq *get_work_gcwq(struct work_struct *work)

/**

 * get_work_pool - return the worker_pool a given work was associated with

 * @work: the work item of interest

 *

 * Return the worker_pool @work was last associated with.  %NULL if none.

 */

static struct worker_pool *get_work_pool(struct work_struct *work)

{

	unsigned long data = atomic_long_read(&work->data);

	unsigned int cpu;

	struct worker_pool *pool;

	int pool_id;



	if (data & WORK_STRUCT_CWQ)

		return ((struct cpu_workqueue_struct *)

			(data & WORK_STRUCT_WQ_DATA_MASK))->pool->gcwq;

			(data & WORK_STRUCT_WQ_DATA_MASK))->pool;



	cpu = data >> WORK_OFFQ_CPU_SHIFT;

	if (cpu == WORK_OFFQ_CPU_NONE)

	pool_id = data >> WORK_OFFQ_POOL_SHIFT;

	if (pool_id == WORK_OFFQ_POOL_NONE)

		return NULL;



	BUG_ON(cpu >= nr_cpu_ids && cpu != WORK_CPU_UNBOUND);

	return get_gcwq(cpu);

	pool = worker_pool_by_id(pool_id);

	WARN_ON_ONCE(!pool);

	return pool;

}



/**

 * get_work_pool_id - return the worker pool ID a given work is associated with

 * @work: the work item of interest

 *

 * Return the worker_pool ID @work was last associated with.

 * %WORK_OFFQ_POOL_NONE if none.

 */

static int get_work_pool_id(struct work_struct *work)

{

	struct worker_pool *pool = get_work_pool(work);



	return pool ? pool->id : WORK_OFFQ_POOL_NONE;

}



static struct global_cwq *get_work_gcwq(struct work_struct *work)

{

	struct worker_pool *pool = get_work_pool(work);



	return pool ? pool->gcwq : NULL;

}



static void mark_work_canceling(struct work_struct *work)

{

	struct global_cwq *gcwq = get_work_gcwq(work);

	unsigned long cpu = gcwq ? gcwq->cpu : WORK_OFFQ_CPU_NONE;

	unsigned long pool_id = get_work_pool_id(work);



	set_work_data(work, (cpu << WORK_OFFQ_CPU_SHIFT) | WORK_OFFQ_CANCELING,

		      WORK_STRUCT_PENDING);

	pool_id <<= WORK_OFFQ_POOL_SHIFT;

	set_work_data(work, pool_id | WORK_OFFQ_CANCELING, WORK_STRUCT_PENDING);

}



static bool work_is_canceling(struct work_struct *work)
@@ -2192,12 +2228,12 @@ __acquires(&gcwq->lock) 
		wake_up_worker(pool);



	/*

	 * Record the last CPU and clear PENDING which should be the last

	 * Record the last pool and clear PENDING which should be the last

	 * update to @work.  Also, do this inside @gcwq->lock so that

	 * PENDING and queued state changes happen together while IRQ is

	 * disabled.

	 */

	set_work_cpu_and_clear_pending(work, gcwq->cpu);

	set_work_pool_and_clear_pending(work, pool->id);



	spin_unlock_irq(&gcwq->lock);
@@ -2967,7 +3003,8 @@ bool cancel_delayed_work(struct delayed_work *dwork) 
	if (unlikely(ret < 0))

		return false;



	set_work_cpu_and_clear_pending(&dwork->work, work_cpu(&dwork->work));

	set_work_pool_and_clear_pending(&dwork->work,

					get_work_pool_id(&dwork->work));

	local_irq_restore(flags);

	return ret;

}
@@ -3430,20 +3467,6 @@ bool workqueue_congested(unsigned int cpu, struct workqueue_struct *wq) 
}

EXPORT_SYMBOL_GPL(workqueue_congested);



/**

 * work_cpu - return the last known associated cpu for @work

 * @work: the work of interest

 *

 * RETURNS:

 * CPU number if @work was ever queued.  WORK_CPU_NONE otherwise.

 */

static unsigned int work_cpu(struct work_struct *work)

{

	struct global_cwq *gcwq = get_work_gcwq(work);



	return gcwq ? gcwq->cpu : WORK_CPU_NONE;

}



/**

 * work_busy - test whether a work is currently pending or running

 * @work: the work to be tested
@@ -3816,9 +3839,9 @@ static int __init init_workqueues(void) 
{

	unsigned int cpu;



	/* make sure we have enough bits for OFFQ CPU number */

	BUILD_BUG_ON((1LU << (BITS_PER_LONG - WORK_OFFQ_CPU_SHIFT)) <

		     WORK_CPU_LAST);

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

	BUILD_BUG_ON((1LU << (BITS_PER_LONG - WORK_OFFQ_POOL_SHIFT)) <

		     WORK_CPU_LAST * NR_STD_WORKER_POOLS);



	cpu_notifier(workqueue_cpu_up_callback, CPU_PRI_WORKQUEUE_UP);

	hotcpu_notifier(workqueue_cpu_down_callback, CPU_PRI_WORKQUEUE_DOWN);