diff options
Diffstat (limited to 'kernel/workqueue.c')
| -rw-r--r-- | kernel/workqueue.c | 94 |
1 files changed, 67 insertions, 27 deletions
diff --git a/kernel/workqueue.c b/kernel/workqueue.c index 7f01a3eeaf95..987293d03ebc 100644 --- a/kernel/workqueue.c +++ b/kernel/workqueue.c @@ -16,9 +16,10 @@ * * This is the generic async execution mechanism. Work items as are * executed in process context. The worker pool is shared and - * automatically managed. There is one worker pool for each CPU and - * one extra for works which are better served by workers which are - * not bound to any specific CPU. + * automatically managed. There are two worker pools for each CPU (one for + * normal work items and the other for high priority ones) and some extra + * pools for workqueues which are not bound to any specific CPU - the + * number of these backing pools is dynamic. * * Please read Documentation/workqueue.txt for details. */ @@ -2039,8 +2040,11 @@ static bool maybe_destroy_workers(struct worker_pool *pool) * multiple times. Does GFP_KERNEL allocations. * * Return: - * spin_lock_irq(pool->lock) which may be released and regrabbed - * multiple times. Does GFP_KERNEL allocations. + * %false if the pool don't need management and the caller can safely start + * processing works, %true indicates that the function released pool->lock + * and reacquired it to perform some management function and that the + * conditions that the caller verified while holding the lock before + * calling the function might no longer be true. */ static bool manage_workers(struct worker *worker) { @@ -2207,6 +2211,15 @@ __acquires(&pool->lock) dump_stack(); } + /* + * The following prevents a kworker from hogging CPU on !PREEMPT + * kernels, where a requeueing work item waiting for something to + * happen could deadlock with stop_machine as such work item could + * indefinitely requeue itself while all other CPUs are trapped in + * stop_machine. + */ + cond_resched(); + spin_lock_irq(&pool->lock); /* clear cpu intensive status */ @@ -2827,6 +2840,19 @@ already_gone: return false; } +static bool __flush_work(struct work_struct *work) +{ + struct wq_barrier barr; + + if (start_flush_work(work, &barr)) { + wait_for_completion(&barr.done); + destroy_work_on_stack(&barr.work); + return true; + } else { + return false; + } +} + /** * flush_work - wait for a work to finish executing the last queueing instance * @work: the work to flush @@ -2840,18 +2866,10 @@ already_gone: */ bool flush_work(struct work_struct *work) { - struct wq_barrier barr; - lock_map_acquire(&work->lockdep_map); lock_map_release(&work->lockdep_map); - if (start_flush_work(work, &barr)) { - wait_for_completion(&barr.done); - destroy_work_on_stack(&barr.work); - return true; - } else { - return false; - } + return __flush_work(work); } EXPORT_SYMBOL_GPL(flush_work); @@ -3095,25 +3113,26 @@ static struct workqueue_struct *dev_to_wq(struct device *dev) return wq_dev->wq; } -static ssize_t wq_per_cpu_show(struct device *dev, - struct device_attribute *attr, char *buf) +static ssize_t per_cpu_show(struct device *dev, struct device_attribute *attr, + char *buf) { struct workqueue_struct *wq = dev_to_wq(dev); return scnprintf(buf, PAGE_SIZE, "%d\n", (bool)!(wq->flags & WQ_UNBOUND)); } +static DEVICE_ATTR_RO(per_cpu); -static ssize_t wq_max_active_show(struct device *dev, - struct device_attribute *attr, char *buf) +static ssize_t max_active_show(struct device *dev, + struct device_attribute *attr, char *buf) { struct workqueue_struct *wq = dev_to_wq(dev); return scnprintf(buf, PAGE_SIZE, "%d\n", wq->saved_max_active); } -static ssize_t wq_max_active_store(struct device *dev, - struct device_attribute *attr, - const char *buf, size_t count) +static ssize_t max_active_store(struct device *dev, + struct device_attribute *attr, const char *buf, + size_t count) { struct workqueue_struct *wq = dev_to_wq(dev); int val; @@ -3124,12 +3143,14 @@ static ssize_t wq_max_active_store(struct device *dev, workqueue_set_max_active(wq, val); return count; } +static DEVICE_ATTR_RW(max_active); -static struct device_attribute wq_sysfs_attrs[] = { - __ATTR(per_cpu, 0444, wq_per_cpu_show, NULL), - __ATTR(max_active, 0644, wq_max_active_show, wq_max_active_store), - __ATTR_NULL, +static struct attribute *wq_sysfs_attrs[] = { + &dev_attr_per_cpu.attr, + &dev_attr_max_active.attr, + NULL, }; +ATTRIBUTE_GROUPS(wq_sysfs); static ssize_t wq_pool_ids_show(struct device *dev, struct device_attribute *attr, char *buf) @@ -3279,7 +3300,7 @@ static struct device_attribute wq_sysfs_unbound_attrs[] = { static struct bus_type wq_subsys = { .name = "workqueue", - .dev_attrs = wq_sysfs_attrs, + .dev_groups = wq_sysfs_groups, }; static int __init wq_sysfs_init(void) @@ -3427,6 +3448,12 @@ static void copy_workqueue_attrs(struct workqueue_attrs *to, { to->nice = from->nice; cpumask_copy(to->cpumask, from->cpumask); + /* + * Unlike hash and equality test, this function doesn't ignore + * ->no_numa as it is used for both pool and wq attrs. Instead, + * get_unbound_pool() explicitly clears ->no_numa after copying. + */ + to->no_numa = from->no_numa; } /* hash value of the content of @attr */ @@ -3598,6 +3625,12 @@ static struct worker_pool *get_unbound_pool(const struct workqueue_attrs *attrs) lockdep_set_subclass(&pool->lock, 1); /* see put_pwq() */ copy_workqueue_attrs(pool->attrs, attrs); + /* + * no_numa isn't a worker_pool attribute, always clear it. See + * 'struct workqueue_attrs' comments for detail. + */ + pool->attrs->no_numa = false; + /* if cpumask is contained inside a NUMA node, we belong to that node */ if (wq_numa_enabled) { for_each_node(node) { @@ -4781,7 +4814,14 @@ long work_on_cpu(int cpu, long (*fn)(void *), void *arg) INIT_WORK_ONSTACK(&wfc.work, work_for_cpu_fn); schedule_work_on(cpu, &wfc.work); - flush_work(&wfc.work); + + /* + * The work item is on-stack and can't lead to deadlock through + * flushing. Use __flush_work() to avoid spurious lockdep warnings + * when work_on_cpu()s are nested. + */ + __flush_work(&wfc.work); + return wfc.ret; } EXPORT_SYMBOL_GPL(work_on_cpu); |