workqueue: Use normal rcu
There is no need for sched_rcu. The undocumented reason why sched_rcu is used is to avoid a few explicit rcu_read_lock()/unlock() pairs by abusing the fact that sched_rcu reader side critical sections are also protected by preempt or irq disabled regions. Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
This commit is contained in:
Thomas Gleixner
parent
59c262358b
commit
91965a4c3d
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@ -129,11 +129,11 @@ enum {
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*
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* PL: wq_pool_mutex protected.
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*
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* PR: wq_pool_mutex protected for writes. Sched-RCU protected for reads.
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* PR: wq_pool_mutex protected for writes. RCU protected for reads.
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*
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* WQ: wq->mutex protected.
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*
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* WR: wq->mutex protected for writes. Sched-RCU protected for reads.
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* WR: wq->mutex protected for writes. RCU protected for reads.
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*
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* MD: wq_mayday_lock protected.
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*/
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@ -178,7 +178,7 @@ struct worker_pool {
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atomic_t nr_running ____cacheline_aligned_in_smp;
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/*
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* Destruction of pool is sched-RCU protected to allow dereferences
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* Destruction of pool is RCU protected to allow dereferences
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* from get_work_pool().
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*/
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struct rcu_head rcu;
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@ -207,7 +207,7 @@ struct pool_workqueue {
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/*
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* Release of unbound pwq is punted to system_wq. See put_pwq()
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* and pwq_unbound_release_workfn() for details. pool_workqueue
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* itself is also sched-RCU protected so that the first pwq can be
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* itself is also RCU protected so that the first pwq can be
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* determined without grabbing wq->mutex.
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*/
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struct work_struct unbound_release_work;
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@ -331,14 +331,14 @@ static void copy_workqueue_attrs(struct workqueue_attrs *to,
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#include <trace/events/workqueue.h>
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#define assert_rcu_or_pool_mutex() \
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rcu_lockdep_assert(rcu_read_lock_sched_held() || \
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rcu_lockdep_assert(rcu_read_lock_held() || \
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lockdep_is_held(&wq_pool_mutex), \
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"sched RCU or wq_pool_mutex should be held")
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"RCU or wq_pool_mutex should be held")
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#define assert_rcu_or_wq_mutex(wq) \
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rcu_lockdep_assert(rcu_read_lock_sched_held() || \
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rcu_lockdep_assert(rcu_read_lock_held() || \
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lockdep_is_held(&wq->mutex), \
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"sched RCU or wq->mutex should be held")
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"RCU or wq->mutex should be held")
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#ifdef CONFIG_LOCKDEP
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#define assert_manager_or_pool_lock(pool) \
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@ -360,7 +360,7 @@ static void copy_workqueue_attrs(struct workqueue_attrs *to,
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* @pool: iteration cursor
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* @pi: integer used for iteration
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*
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* This must be called either with wq_pool_mutex held or sched RCU read
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* This must be called either with wq_pool_mutex held or RCU read
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* locked. If the pool needs to be used beyond the locking in effect, the
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* caller is responsible for guaranteeing that the pool stays online.
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*
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@ -393,7 +393,7 @@ static void copy_workqueue_attrs(struct workqueue_attrs *to,
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* @pwq: iteration cursor
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* @wq: the target workqueue
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*
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* This must be called either with wq->mutex held or sched RCU read locked.
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* This must be called either with wq->mutex held or RCU read locked.
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* If the pwq needs to be used beyond the locking in effect, the caller is
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* responsible for guaranteeing that the pwq stays online.
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*
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@ -548,7 +548,7 @@ static int worker_pool_assign_id(struct worker_pool *pool)
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* @wq: the target workqueue
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* @node: the node ID
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*
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* This must be called either with pwq_lock held or sched RCU read locked.
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* This must be called either with pwq_lock held or RCU read locked.
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* If the pwq needs to be used beyond the locking in effect, the caller is
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* responsible for guaranteeing that the pwq stays online.
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*
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@ -652,8 +652,8 @@ static struct pool_workqueue *get_work_pwq(struct work_struct *work)
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* @work: the work item of interest
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*
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* Pools are created and destroyed under wq_pool_mutex, and allows read
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* access under sched-RCU read lock. As such, this function should be
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* called under wq_pool_mutex or with preemption disabled.
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* access under RCU read lock. As such, this function should be
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* called under wq_pool_mutex or inside of a rcu_read_lock() region.
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*
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* All fields of the returned pool are accessible as long as the above
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* mentioned locking is in effect. If the returned pool needs to be used
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@ -1086,7 +1086,7 @@ static void put_pwq_unlocked(struct pool_workqueue *pwq)
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{
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if (pwq) {
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/*
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* As both pwqs and pools are sched-RCU protected, the
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* As both pwqs and pools are RCU protected, the
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* following lock operations are safe.
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*/
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spin_lock_irq(&pwq->pool->lock);
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@ -1212,6 +1212,7 @@ static int try_to_grab_pending(struct work_struct *work, bool is_dwork,
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if (!test_and_set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(work)))
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return 0;
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rcu_read_lock();
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/*
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* The queueing is in progress, or it is already queued. Try to
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* steal it from ->worklist without clearing WORK_STRUCT_PENDING.
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@ -1250,10 +1251,12 @@ static int try_to_grab_pending(struct work_struct *work, bool is_dwork,
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set_work_pool_and_keep_pending(work, pool->id);
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spin_unlock(&pool->lock);
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rcu_read_unlock();
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return 1;
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}
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spin_unlock(&pool->lock);
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fail:
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rcu_read_unlock();
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local_irq_restore(*flags);
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if (work_is_canceling(work))
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return -ENOENT;
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@ -1334,6 +1337,8 @@ static void __queue_work(int cpu, struct workqueue_struct *wq,
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if (unlikely(wq->flags & __WQ_DRAINING) &&
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WARN_ON_ONCE(!is_chained_work(wq)))
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return;
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rcu_read_lock();
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retry:
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if (req_cpu == WORK_CPU_UNBOUND)
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cpu = raw_smp_processor_id();
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@ -1390,10 +1395,8 @@ retry:
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/* pwq determined, queue */
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trace_workqueue_queue_work(req_cpu, pwq, work);
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if (WARN_ON(!list_empty(&work->entry))) {
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spin_unlock(&pwq->pool->lock);
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return;
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}
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if (WARN_ON(!list_empty(&work->entry)))
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goto out;
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pwq->nr_in_flight[pwq->work_color]++;
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work_flags = work_color_to_flags(pwq->work_color);
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@ -1409,7 +1412,9 @@ retry:
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insert_work(pwq, work, worklist, work_flags);
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out:
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spin_unlock(&pwq->pool->lock);
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rcu_read_unlock();
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}
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/**
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@ -2824,14 +2829,14 @@ static bool start_flush_work(struct work_struct *work, struct wq_barrier *barr)
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might_sleep();
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local_irq_disable();
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rcu_read_lock();
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pool = get_work_pool(work);
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if (!pool) {
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local_irq_enable();
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rcu_read_unlock();
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return false;
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}
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spin_lock(&pool->lock);
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spin_lock_irq(&pool->lock);
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/* see the comment in try_to_grab_pending() with the same code */
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pwq = get_work_pwq(work);
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if (pwq) {
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@ -2858,10 +2863,11 @@ static bool start_flush_work(struct work_struct *work, struct wq_barrier *barr)
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else
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lock_map_acquire_read(&pwq->wq->lockdep_map);
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lock_map_release(&pwq->wq->lockdep_map);
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rcu_read_unlock();
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return true;
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already_gone:
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spin_unlock_irq(&pool->lock);
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rcu_read_unlock();
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return false;
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}
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@ -3227,7 +3233,8 @@ static ssize_t wq_pool_ids_show(struct device *dev,
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const char *delim = "";
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int node, written = 0;
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rcu_read_lock_sched();
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get_online_cpus();
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rcu_read_lock();
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for_each_node(node) {
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written += scnprintf(buf + written, PAGE_SIZE - written,
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"%s%d:%d", delim, node,
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@ -3235,7 +3242,8 @@ static ssize_t wq_pool_ids_show(struct device *dev,
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delim = " ";
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}
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written += scnprintf(buf + written, PAGE_SIZE - written, "\n");
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rcu_read_unlock_sched();
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rcu_read_unlock();
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put_online_cpus();
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return written;
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}
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@ -3602,7 +3610,7 @@ static void rcu_free_pool(struct rcu_head *rcu)
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* put_unbound_pool - put a worker_pool
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* @pool: worker_pool to put
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*
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* Put @pool. If its refcnt reaches zero, it gets destroyed in sched-RCU
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* Put @pool. If its refcnt reaches zero, it gets destroyed in RCU
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* safe manner. get_unbound_pool() calls this function on its failure path
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* and this function should be able to release pools which went through,
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* successfully or not, init_worker_pool().
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@ -3649,8 +3657,8 @@ static void put_unbound_pool(struct worker_pool *pool)
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del_timer_sync(&pool->idle_timer);
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del_timer_sync(&pool->mayday_timer);
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/* sched-RCU protected to allow dereferences from get_work_pool() */
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call_rcu_sched(&pool->rcu, rcu_free_pool);
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/* RCU protected to allow dereferences from get_work_pool() */
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call_rcu(&pool->rcu, rcu_free_pool);
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}
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/**
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@ -3763,7 +3771,7 @@ static void pwq_unbound_release_workfn(struct work_struct *work)
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put_unbound_pool(pool);
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mutex_unlock(&wq_pool_mutex);
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call_rcu_sched(&pwq->rcu, rcu_free_pwq);
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call_rcu(&pwq->rcu, rcu_free_pwq);
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/*
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* If we're the last pwq going away, @wq is already dead and no one
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@ -4477,7 +4485,8 @@ bool workqueue_congested(int cpu, struct workqueue_struct *wq)
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struct pool_workqueue *pwq;
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bool ret;
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rcu_read_lock_sched();
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rcu_read_lock();
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preempt_disable();
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if (cpu == WORK_CPU_UNBOUND)
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cpu = smp_processor_id();
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@ -4488,7 +4497,8 @@ bool workqueue_congested(int cpu, struct workqueue_struct *wq)
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pwq = unbound_pwq_by_node(wq, cpu_to_node(cpu));
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ret = !list_empty(&pwq->delayed_works);
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rcu_read_unlock_sched();
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preempt_enable();
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rcu_read_unlock();
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return ret;
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}
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@ -4514,16 +4524,15 @@ unsigned int work_busy(struct work_struct *work)
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if (work_pending(work))
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ret |= WORK_BUSY_PENDING;
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local_irq_save(flags);
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rcu_read_lock()
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pool = get_work_pool(work);
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if (pool) {
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spin_lock(&pool->lock);
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spin_lock_irqsave(&pool->lock, flags);
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if (find_worker_executing_work(pool, work))
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ret |= WORK_BUSY_RUNNING;
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spin_unlock(&pool->lock);
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spin_unlock_irqrestore(&pool->lock, flags);
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}
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local_irq_restore(flags);
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rcu_read_unlock();
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return ret;
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}
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EXPORT_SYMBOL_GPL(work_busy);
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@ -4971,16 +4980,16 @@ bool freeze_workqueues_busy(void)
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* nr_active is monotonically decreasing. It's safe
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* to peek without lock.
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*/
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rcu_read_lock_sched();
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rcu_read_lock();
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for_each_pwq(pwq, wq) {
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WARN_ON_ONCE(pwq->nr_active < 0);
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if (pwq->nr_active) {
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busy = true;
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rcu_read_unlock_sched();
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rcu_read_unlock();
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goto out_unlock;
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}
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}
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rcu_read_unlock_sched();
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rcu_read_unlock();
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}
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out_unlock:
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mutex_unlock(&wq_pool_mutex);
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