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-rw-r--r--kernel/workqueue.c68
1 files changed, 63 insertions, 5 deletions
diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index 942421443603..3dc83d5eba50 100644
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -212,6 +212,7 @@ struct worker_pool {
enum pool_workqueue_stats {
PWQ_STAT_STARTED, /* work items started execution */
PWQ_STAT_COMPLETED, /* work items completed execution */
+ PWQ_STAT_CPU_INTENSIVE, /* wq_cpu_intensive_thresh_us violations */
PWQ_STAT_CM_WAKEUP, /* concurrency-management worker wakeups */
PWQ_STAT_MAYDAY, /* maydays to rescuer */
PWQ_STAT_RESCUED, /* linked work items executed by rescuer */
@@ -332,6 +333,14 @@ static struct kmem_cache *pwq_cache;
static cpumask_var_t *wq_numa_possible_cpumask;
/* possible CPUs of each node */
+/*
+ * Per-cpu work items which run for longer than the following threshold are
+ * automatically considered CPU intensive and excluded from concurrency
+ * management to prevent them from noticeably delaying other per-cpu work items.
+ */
+static unsigned long wq_cpu_intensive_thresh_us = 10000;
+module_param_named(cpu_intensive_thresh_us, wq_cpu_intensive_thresh_us, ulong, 0644);
+
static bool wq_disable_numa;
module_param_named(disable_numa, wq_disable_numa, bool, 0444);
@@ -962,6 +971,13 @@ void wq_worker_running(struct task_struct *task)
if (!(worker->flags & WORKER_NOT_RUNNING))
worker->pool->nr_running++;
preempt_enable();
+
+ /*
+ * CPU intensive auto-detection cares about how long a work item hogged
+ * CPU without sleeping. Reset the starting timestamp on wakeup.
+ */
+ worker->current_at = worker->task->se.sum_exec_runtime;
+
worker->sleeping = 0;
}
@@ -1013,6 +1029,45 @@ void wq_worker_sleeping(struct task_struct *task)
}
/**
+ * wq_worker_tick - a scheduler tick occurred while a kworker is running
+ * @task: task currently running
+ *
+ * Called from scheduler_tick(). We're in the IRQ context and the current
+ * worker's fields which follow the 'K' locking rule can be accessed safely.
+ */
+void wq_worker_tick(struct task_struct *task)
+{
+ struct worker *worker = kthread_data(task);
+ struct pool_workqueue *pwq = worker->current_pwq;
+ struct worker_pool *pool = worker->pool;
+
+ if (!pwq)
+ return;
+
+ /*
+ * If the current worker is concurrency managed and hogged the CPU for
+ * longer than wq_cpu_intensive_thresh_us, it's automatically marked
+ * CPU_INTENSIVE to avoid stalling other concurrency-managed work items.
+ */
+ if ((worker->flags & WORKER_NOT_RUNNING) ||
+ worker->task->se.sum_exec_runtime - worker->current_at <
+ wq_cpu_intensive_thresh_us * NSEC_PER_USEC)
+ return;
+
+ raw_spin_lock(&pool->lock);
+
+ worker_set_flags(worker, WORKER_CPU_INTENSIVE);
+ pwq->stats[PWQ_STAT_CPU_INTENSIVE]++;
+
+ if (need_more_worker(pool)) {
+ pwq->stats[PWQ_STAT_CM_WAKEUP]++;
+ wake_up_worker(pool);
+ }
+
+ raw_spin_unlock(&pool->lock);
+}
+
+/**
* wq_worker_last_func - retrieve worker's last work function
* @task: Task to retrieve last work function of.
*
@@ -2327,7 +2382,6 @@ __acquires(&pool->lock)
{
struct pool_workqueue *pwq = get_work_pwq(work);
struct worker_pool *pool = worker->pool;
- bool cpu_intensive = pwq->wq->flags & WQ_CPU_INTENSIVE;
unsigned long work_data;
struct worker *collision;
#ifdef CONFIG_LOCKDEP
@@ -2364,6 +2418,7 @@ __acquires(&pool->lock)
worker->current_work = work;
worker->current_func = work->func;
worker->current_pwq = pwq;
+ worker->current_at = worker->task->se.sum_exec_runtime;
work_data = *work_data_bits(work);
worker->current_color = get_work_color(work_data);
@@ -2381,7 +2436,7 @@ __acquires(&pool->lock)
* of concurrency management and the next code block will chain
* execution of the pending work items.
*/
- if (unlikely(cpu_intensive))
+ if (unlikely(pwq->wq->flags & WQ_CPU_INTENSIVE))
worker_set_flags(worker, WORKER_CPU_INTENSIVE);
/*
@@ -2461,9 +2516,12 @@ __acquires(&pool->lock)
raw_spin_lock_irq(&pool->lock);
- /* clear cpu intensive status */
- if (unlikely(cpu_intensive))
- worker_clr_flags(worker, WORKER_CPU_INTENSIVE);
+ /*
+ * In addition to %WQ_CPU_INTENSIVE, @worker may also have been marked
+ * CPU intensive by wq_worker_tick() if @work hogged CPU longer than
+ * wq_cpu_intensive_thresh_us. Clear it.
+ */
+ worker_clr_flags(worker, WORKER_CPU_INTENSIVE);
/* tag the worker for identification in schedule() */
worker->last_func = worker->current_func;