文章系列

1.linux工作队列 - workqueue总览
2.linux工作队列 - workqueue_struct创建
3.linux工作队列 - 把work_struct加入工作队列
4.linux工作队列 - work_struct被调用过程

把work_struct加入工作队列

把work_struct加入到工作队列workqueue的API在系列文章1有介绍，这些API虽然用法不一，但是最终都会调用__queue_work（）函数来进行实际加入操作，比如API：queue_work_on： bool queue_work_on(int cpu, struct workqueue_struct *wq, struct work_struct *work) { bool ret = false; unsigned long flags; local_irq_save(flags); if (!test_and_set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(work))) { __queue_work(cpu, wq, work);------调用到__queue_work ret = true; } local_irq_restore(flags); return ret; } 下面分析__queue_work的代码，如下： static void __queue_work(int cpu, struct workqueue_struct *wq, struct work_struct *work) { struct pool_workqueue *pwq; struct worker_pool *last_pool; struct list_head *worklist; unsigned int work_flags; unsigned int req_cpu = cpu; /* * While a work item is PENDING && off queue, a task trying to * steal the PENDING will busy-loop waiting for it to either get * queued or lose PENDING. Grabbing PENDING and queueing should * happen with IRQ disabled. */ WARN_ON_ONCE(!irqs_disabled()); debug_work_activate(work); /* if draining, only works from the same workqueue are allowed */ if (unlikely(wq->flags & __WQ_DRAINING) && WARN_ON_ONCE(!is_chained_work(wq))) return; retry: if (req_cpu == WORK_CPU_UNBOUND) cpu = wq_select_unbound_cpu(raw_smp_processor_id()); //根据传入的参数struct workqueue_struct *wq来选择需要的类型 /* pwq which will be used unless @work is executing elsewhere */ if (!(wq->flags & WQ_UNBOUND)) pwq = per_cpu_ptr(wq->cpu_pwqs, cpu);----------------得到bound类型的pool_workqueue else pwq = unbound_pwq_by_node(wq, cpu_to_node(cpu));-----得到unbound类型的pool_workqueue /* * If @work was previously on a different pool, it might still be * running there, in which case the work needs to be queued on that * pool to guarantee non-reentrancy. */ //work有可能已经存在另一个不同的work pool中，它可能仍旧在运行，为了避免重入，work仍然要加入到原来的work pool last_pool = get_work_pool(work); if (last_pool && last_pool != pwq->pool) { struct worker *worker; spin_lock(&last_pool->lock); worker = find_worker_executing_work(last_pool, work); if (worker && worker->current_pwq->wq == wq) { pwq = worker->current_pwq;----------------------得到last的pool_workqueue } else { /* meh... not running there, queue here */ spin_unlock(&last_pool->lock); spin_lock(&pwq->pool->lock); } } else { spin_lock(&pwq->pool->lock); } /* * pwq is determined and locked. For unbound pools, we could have * raced with pwq release and it could already be dead. If its * refcnt is zero, repeat pwq selection. Note that pwqs never die * without another pwq replacing it in the numa_pwq_tbl or while * work items are executing on it, so the retrying is guaranteed to * make forward-progress. */ if (unlikely(!pwq->refcnt)) { if (wq->flags & WQ_UNBOUND) { spin_unlock(&pwq->pool->lock); cpu_relax(); goto retry; } /* oops */ WARN_ONCE(true, "workqueue: per-cpu pwq for %s on cpu%d has 0 refcnt", wq->name, cpu); } /* pwq determined, queue */ trace_workqueue_queue_work(req_cpu, pwq, work); if (WARN_ON(!list_empty(&work->entry))) { spin_unlock(&pwq->pool->lock); return; } pwq->nr_in_flight[pwq->work_color]++; work_flags = work_color_to_flags(pwq->work_color); if (likely(pwq->nr_active < pwq->max_active)) { trace_workqueue_activate_work(work); pwq->nr_active++; worklist = &pwq->pool->worklist;----------------得到pool_workqueue的worker_pool的worklist if (list_empty(worklist)) pwq->pool->watchdog_ts = jiffies; } else { work_flags |= WORK_STRUCT_DELAYED; worklist = &pwq->delayed_works; } insert_work(pwq, work, worklist, work_flags);-----把work加入到worklist，并唤醒 spin_unlock(&pwq->pool->lock); } 看函数insert_work代码： static void insert_work(struct pool_workqueue *pwq, struct work_struct *work, struct list_head *head, unsigned int extra_flags) { struct worker_pool *pool = pwq->pool; /* we own @work, set data and link */ set_work_pwq(work, pwq, extra_flags); list_add_tail(&work->entry, head);---------------加入work pool的链表 get_pwq(pwq); /* * Ensure either wq_worker_sleeping() sees the above * list_add_tail() or we see zero nr_running to avoid workers lying * around lazily while there are works to be processed. */ smp_mb(); if (__need_more_worker(pool)) wake_up_worker(pool);----------------------唤醒work pool }