workqueue: Use normal rcu

 *

 * PL: wq_pool_mutex protected.

 *

 * PR: wq_pool_mutex protected for writes.  Sched-RCU protected for reads.

 * PR: wq_pool_mutex protected for writes.  RCU protected for reads.

 *

 * PW: wq_pool_mutex and wq->mutex protected for writes.  Either for reads.

 *

 * PWR: wq_pool_mutex and wq->mutex protected for writes.  Either or

 *      sched-RCU for reads.

 *      RCU for reads.

 *

 * WQ: wq->mutex protected.

 *

 * WR: wq->mutex protected for writes.  Sched-RCU protected for reads.

 * WR: wq->mutex protected for writes.  RCU protected for reads.

 *

 * MD: wq_mayday_lock protected.

 */

	atomic_t		nr_running ____cacheline_aligned_in_smp;

	/*

	 * Destruction of pool is sched-RCU protected to allow dereferences

	 * Destruction of pool is RCU protected to allow dereferences

	 * from get_work_pool().

	 */

	struct rcu_head		rcu;

	/*

	 * Release of unbound pwq is punted to system_wq.  See put_pwq()

	 * and pwq_unbound_release_workfn() for details.  pool_workqueue

	 * itself is also sched-RCU protected so that the first pwq can be

	 * itself is also RCU protected so that the first pwq can be

	 * determined without grabbing wq->mutex.

	 */

	struct work_struct	unbound_release_work;

	char			name[WQ_NAME_LEN]; /* I: workqueue name */

	/*

	 * Destruction of workqueue_struct is sched-RCU protected to allow

	 * walking the workqueues list without grabbing wq_pool_mutex.

	 * Destruction of workqueue_struct is RCU protected to allow walking

	 * the workqueues list without grabbing wq_pool_mutex.

	 * This is used to dump all workqueues from sysrq.

	 */

	struct rcu_head		rcu;

#include <trace/events/workqueue.h>

#define assert_rcu_or_pool_mutex()					\

	RCU_LOCKDEP_WARN(!rcu_read_lock_sched_held() &&			\

	RCU_LOCKDEP_WARN(!rcu_read_lock_held() &&			\

			 !lockdep_is_held(&wq_pool_mutex),		\

			 "sched RCU or wq_pool_mutex should be held")

			 "RCU or wq_pool_mutex should be held")

#define assert_rcu_or_wq_mutex(wq)					\

	RCU_LOCKDEP_WARN(!rcu_read_lock_sched_held() &&			\

	RCU_LOCKDEP_WARN(!rcu_read_lock_held() &&			\

			 !lockdep_is_held(&wq->mutex),			\

			 "sched RCU or wq->mutex should be held")

			 "RCU or wq->mutex should be held")

#define assert_rcu_or_wq_mutex_or_pool_mutex(wq)			\

	RCU_LOCKDEP_WARN(!rcu_read_lock_sched_held() &&			\

	RCU_LOCKDEP_WARN(!rcu_read_lock_held() &&			\

			 !lockdep_is_held(&wq->mutex) &&		\

			 !lockdep_is_held(&wq_pool_mutex),		\

			 "sched RCU, wq->mutex or wq_pool_mutex should be held")

			 "RCU, wq->mutex or wq_pool_mutex should be held")

#define for_each_cpu_worker_pool(pool, cpu)				\

	for ((pool) = &per_cpu(cpu_worker_pools, cpu)[0];		\

 * @pool: iteration cursor

 * @pi: integer used for iteration

 *

 * This must be called either with wq_pool_mutex held or sched RCU read

 * This must be called either with wq_pool_mutex held or RCU read

 * locked.  If the pool needs to be used beyond the locking in effect, the

 * caller is responsible for guaranteeing that the pool stays online.

 *

 * @pwq: iteration cursor

 * @wq: the target workqueue

 *

 * This must be called either with wq->mutex held or sched RCU read locked.

 * This must be called either with wq->mutex held or RCU read locked.

 * If the pwq needs to be used beyond the locking in effect, the caller is

 * responsible for guaranteeing that the pwq stays online.

 *

 * @wq: the target workqueue

 * @node: the node ID

 *

 * This must be called with any of wq_pool_mutex, wq->mutex or sched RCU

 * This must be called with any of wq_pool_mutex, wq->mutex or RCU

 * read locked.

 * If the pwq needs to be used beyond the locking in effect, the caller is

 * responsible for guaranteeing that the pwq stays online.

 * @work: the work item of interest

 *

 * Pools are created and destroyed under wq_pool_mutex, and allows read

 * access under sched-RCU read lock.  As such, this function should be

 * called under wq_pool_mutex or with preemption disabled.

 * access under RCU read lock.  As such, this function should be

 * called under wq_pool_mutex or inside of a rcu_read_lock() region.

 *

 * All fields of the returned pool are accessible as long as the above

 * mentioned locking is in effect.  If the returned pool needs to be used

{

	if (pwq) {

		/*

		 * As both pwqs and pools are sched-RCU protected, the

		 * As both pwqs and pools are RCU protected, the

		 * following lock operations are safe.

		 */

		spin_lock_irq(&pwq->pool->lock);

	if (!test_and_set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(work)))

		return 0;

	rcu_read_lock();

	/*

	 * The queueing is in progress, or it is already queued. Try to

	 * steal it from ->worklist without clearing WORK_STRUCT_PENDING.

		set_work_pool_and_keep_pending(work, pool->id);

		spin_unlock(&pool->lock);

		rcu_read_unlock();

		return 1;

	}

	spin_unlock(&pool->lock);

fail:

	rcu_read_unlock();

	local_irq_restore(*flags);

	if (work_is_canceling(work))

		return -ENOENT;

	if (unlikely(wq->flags & __WQ_DRAINING) &&

	    WARN_ON_ONCE(!is_chained_work(wq)))

		return;

	rcu_read_lock();

retry:

	if (req_cpu == WORK_CPU_UNBOUND)

		cpu = wq_select_unbound_cpu(raw_smp_processor_id());

	/* pwq determined, queue */

	trace_workqueue_queue_work(req_cpu, pwq, work);

	if (WARN_ON(!list_empty(&work->entry))) {

		spin_unlock(&pwq->pool->lock);

		return;

	}

	if (WARN_ON(!list_empty(&work->entry)))

		goto out;

	pwq->nr_in_flight[pwq->work_color]++;

	work_flags = work_color_to_flags(pwq->work_color);

	insert_work(pwq, work, worklist, work_flags);

out:

	spin_unlock(&pwq->pool->lock);

	rcu_read_unlock();

}

/**

	might_sleep();

	local_irq_disable();

	rcu_read_lock();

	pool = get_work_pool(work);

	if (!pool) {

		local_irq_enable();

		rcu_read_unlock();

		return false;

	}

	spin_lock(&pool->lock);

	spin_lock_irq(&pool->lock);

	/* see the comment in try_to_grab_pending() with the same code */

	pwq = get_work_pwq(work);

	if (pwq) {

		lock_map_acquire(&pwq->wq->lockdep_map);

		lock_map_release(&pwq->wq->lockdep_map);

	}

	rcu_read_unlock();

	return true;

already_gone:

	spin_unlock_irq(&pool->lock);

	rcu_read_unlock();

	return false;

}

 * put_unbound_pool - put a worker_pool

 * @pool: worker_pool to put

 *

 * Put @pool.  If its refcnt reaches zero, it gets destroyed in sched-RCU

 * Put @pool.  If its refcnt reaches zero, it gets destroyed in RCU

 * safe manner.  get_unbound_pool() calls this function on its failure path

 * and this function should be able to release pools which went through,

 * successfully or not, init_worker_pool().

	del_timer_sync(&pool->idle_timer);

	del_timer_sync(&pool->mayday_timer);

	/* sched-RCU protected to allow dereferences from get_work_pool() */

	/* RCU protected to allow dereferences from get_work_pool() */

	call_rcu(&pool->rcu, rcu_free_pool);

}

	struct pool_workqueue *pwq;

	bool ret;

	rcu_read_lock_sched();

	rcu_read_lock();

	preempt_disable();

	if (cpu == WORK_CPU_UNBOUND)

		cpu = smp_processor_id();

		pwq = unbound_pwq_by_node(wq, cpu_to_node(cpu));

	ret = !list_empty(&pwq->delayed_works);

	rcu_read_unlock_sched();

	preempt_enable();

	rcu_read_unlock();

	return ret;

}

	if (work_pending(work))

		ret |= WORK_BUSY_PENDING;

	local_irq_save(flags);

	rcu_read_lock();

	pool = get_work_pool(work);

	if (pool) {

		spin_lock(&pool->lock);

		spin_lock_irqsave(&pool->lock, flags);

		if (find_worker_executing_work(pool, work))

			ret |= WORK_BUSY_RUNNING;

		spin_unlock(&pool->lock);

		spin_unlock_irqrestore(&pool->lock, flags);

	}

	local_irq_restore(flags);

	rcu_read_unlock();

	return ret;

}

	unsigned long flags;

	int pi;

	rcu_read_lock_sched();

	rcu_read_lock();

	pr_info("Showing busy workqueues and worker pools:\n");

		touch_nmi_watchdog();

	}

	rcu_read_unlock_sched();

	rcu_read_unlock();

}

/* used to show worker information through /proc/PID/{comm,stat,status} */

		 * nr_active is monotonically decreasing.  It's safe

		 * to peek without lock.

		 */

		rcu_read_lock_sched();

		rcu_read_lock();

		for_each_pwq(pwq, wq) {

			WARN_ON_ONCE(pwq->nr_active < 0);

			if (pwq->nr_active) {

				busy = true;

				rcu_read_unlock_sched();

				rcu_read_unlock();

				goto out_unlock;

			}

		}

		rcu_read_unlock_sched();

		rcu_read_unlock();

	}

out_unlock:

	mutex_unlock(&wq_pool_mutex);

	const char *delim = "";

	int node, written = 0;

	rcu_read_lock_sched();

	get_online_cpus();

	rcu_read_lock();

	for_each_node(node) {

		written += scnprintf(buf + written, PAGE_SIZE - written,

				     "%s%d:%d", delim, node,

		delim = " ";

	}

	written += scnprintf(buf + written, PAGE_SIZE - written, "\n");

	rcu_read_unlock_sched();

	rcu_read_unlock();

	put_online_cpus();

	return written;

}