diff options
| -rw-r--r-- | include/linux/workqueue.h | 21 | ||||
| -rw-r--r-- | kernel/workqueue.c | 355 |
2 files changed, 322 insertions, 54 deletions
diff --git a/include/linux/workqueue.h b/include/linux/workqueue.h index b90958a..8762f62 100644 --- a/include/linux/workqueue.h +++ b/include/linux/workqueue.h @@ -26,11 +26,13 @@ enum { WORK_STRUCT_PENDING_BIT = 0, /* work item is pending execution */ #ifdef CONFIG_DEBUG_OBJECTS_WORK WORK_STRUCT_STATIC_BIT = 1, /* static initializer (debugobjects) */ - WORK_STRUCT_FLAG_BITS = 2, + WORK_STRUCT_COLOR_SHIFT = 3, /* color for workqueue flushing */ #else - WORK_STRUCT_FLAG_BITS = 1, + WORK_STRUCT_COLOR_SHIFT = 2, /* color for workqueue flushing */ #endif + WORK_STRUCT_COLOR_BITS = 4, + WORK_STRUCT_PENDING = 1 << WORK_STRUCT_PENDING_BIT, #ifdef CONFIG_DEBUG_OBJECTS_WORK WORK_STRUCT_STATIC = 1 << WORK_STRUCT_STATIC_BIT, @@ -38,6 +40,21 @@ enum { WORK_STRUCT_STATIC = 0, #endif + /* + * The last color is no color used for works which don't + * participate in workqueue flushing. + */ + WORK_NR_COLORS = (1 << WORK_STRUCT_COLOR_BITS) - 1, + WORK_NO_COLOR = WORK_NR_COLORS, + + /* + * Reserve 6 bits off of cwq pointer w/ debugobjects turned + * off. This makes cwqs aligned to 64 bytes which isn't too + * excessive while allowing 15 workqueue flush colors. + */ + WORK_STRUCT_FLAG_BITS = WORK_STRUCT_COLOR_SHIFT + + WORK_STRUCT_COLOR_BITS, + WORK_STRUCT_FLAG_MASK = (1UL << WORK_STRUCT_FLAG_BITS) - 1, WORK_STRUCT_WQ_DATA_MASK = ~WORK_STRUCT_FLAG_MASK, }; diff --git a/kernel/workqueue.c b/kernel/workqueue.c index 74a3849..56e47c5 100644 --- a/kernel/workqueue.c +++ b/kernel/workqueue.c @@ -41,6 +41,8 @@ * * L: cwq->lock protected. Access with cwq->lock held. * + * F: wq->flush_mutex protected. + * * W: workqueue_lock protected. */ @@ -60,10 +62,23 @@ struct cpu_workqueue_struct { unsigned int cpu; struct workqueue_struct *wq; /* I: the owning workqueue */ + int work_color; /* L: current color */ + int flush_color; /* L: flushing color */ + int nr_in_flight[WORK_NR_COLORS]; + /* L: nr of in_flight works */ struct task_struct *thread; }; /* + * Structure used to wait for workqueue flush. + */ +struct wq_flusher { + struct list_head list; /* F: list of flushers */ + int flush_color; /* F: flush color waiting for */ + struct completion done; /* flush completion */ +}; + +/* * The externally visible workqueue abstraction is an array of * per-CPU workqueues: */ @@ -71,6 +86,15 @@ struct workqueue_struct { unsigned int flags; /* I: WQ_* flags */ struct cpu_workqueue_struct *cpu_wq; /* I: cwq's */ struct list_head list; /* W: list of all workqueues */ + + struct mutex flush_mutex; /* protects wq flushing */ + int work_color; /* F: current work color */ + int flush_color; /* F: current flush color */ + atomic_t nr_cwqs_to_flush; /* flush in progress */ + struct wq_flusher *first_flusher; /* F: first flusher */ + struct list_head flusher_queue; /* F: flush waiters */ + struct list_head flusher_overflow; /* F: flush overflow list */ + const char *name; /* I: workqueue name */ #ifdef CONFIG_LOCKDEP struct lockdep_map lockdep_map; @@ -207,6 +231,22 @@ static struct cpu_workqueue_struct *target_cwq(unsigned int cpu, return get_cwq(cpu, wq); } +static unsigned int work_color_to_flags(int color) +{ + return color << WORK_STRUCT_COLOR_SHIFT; +} + +static int get_work_color(struct work_struct *work) +{ + return (*work_data_bits(work) >> WORK_STRUCT_COLOR_SHIFT) & + ((1 << WORK_STRUCT_COLOR_BITS) - 1); +} + +static int work_next_color(int color) +{ + return (color + 1) % WORK_NR_COLORS; +} + /* * Set the workqueue on which a work item is to be run * - Must *only* be called if the pending flag is set @@ -273,7 +313,9 @@ static void __queue_work(unsigned int cpu, struct workqueue_struct *wq, debug_work_activate(work); spin_lock_irqsave(&cwq->lock, flags); BUG_ON(!list_empty(&work->entry)); - insert_work(cwq, work, &cwq->worklist, 0); + cwq->nr_in_flight[cwq->work_color]++; + insert_work(cwq, work, &cwq->worklist, + work_color_to_flags(cwq->work_color)); spin_unlock_irqrestore(&cwq->lock, flags); } @@ -387,6 +429,44 @@ int queue_delayed_work_on(int cpu, struct workqueue_struct *wq, EXPORT_SYMBOL_GPL(queue_delayed_work_on); /** + * cwq_dec_nr_in_flight - decrement cwq's nr_in_flight + * @cwq: cwq of interest + * @color: color of work which left the queue + * + * A work either has completed or is removed from pending queue, + * decrement nr_in_flight of its cwq and handle workqueue flushing. + * + * CONTEXT: + * spin_lock_irq(cwq->lock). + */ +static void cwq_dec_nr_in_flight(struct cpu_workqueue_struct *cwq, int color) +{ + /* ignore uncolored works */ + if (color == WORK_NO_COLOR) + return; + + cwq->nr_in_flight[color]--; + + /* is flush in progress and are we at the flushing tip? */ + if (likely(cwq->flush_color != color)) + return; + + /* are there still in-flight works? */ + if (cwq->nr_in_flight[color]) + return; + + /* this cwq is done, clear flush_color */ + cwq->flush_color = -1; + + /* + * If this was the last cwq, wake up the first flusher. It + * will handle the rest. + */ + if (atomic_dec_and_test(&cwq->wq->nr_cwqs_to_flush)) + complete(&cwq->wq->first_flusher->done); +} + +/** * process_one_work - process single work * @cwq: cwq to process work for * @work: work to process @@ -404,6 +484,7 @@ static void process_one_work(struct cpu_workqueue_struct *cwq, struct work_struct *work) { work_func_t f = work->func; + int work_color; #ifdef CONFIG_LOCKDEP /* * It is permissible to free the struct work_struct from @@ -417,6 +498,7 @@ static void process_one_work(struct cpu_workqueue_struct *cwq, /* claim and process */ debug_work_deactivate(work); cwq->current_work = work; + work_color = get_work_color(work); list_del_init(&work->entry); spin_unlock_irq(&cwq->lock); @@ -443,6 +525,7 @@ static void process_one_work(struct cpu_workqueue_struct *cwq, /* we're done with it, release */ cwq->current_work = NULL; + cwq_dec_nr_in_flight(cwq, work_color); } static void run_workqueue(struct cpu_workqueue_struct *cwq) @@ -529,29 +612,78 @@ static void insert_wq_barrier(struct cpu_workqueue_struct *cwq, init_completion(&barr->done); debug_work_activate(&barr->work); - insert_work(cwq, &barr->work, head, 0); + insert_work(cwq, &barr->work, head, work_color_to_flags(WORK_NO_COLOR)); } -static int flush_cpu_workqueue(struct cpu_workqueue_struct *cwq) +/** + * flush_workqueue_prep_cwqs - prepare cwqs for workqueue flushing + * @wq: workqueue being flushed + * @flush_color: new flush color, < 0 for no-op + * @work_color: new work color, < 0 for no-op + * + * Prepare cwqs for workqueue flushing. + * + * If @flush_color is non-negative, flush_color on all cwqs should be + * -1. If no cwq has in-flight commands at the specified color, all + * cwq->flush_color's stay at -1 and %false is returned. If any cwq + * has in flight commands, its cwq->flush_color is set to + * @flush_color, @wq->nr_cwqs_to_flush is updated accordingly, cwq + * wakeup logic is armed and %true is returned. + * + * The caller should have initialized @wq->first_flusher prior to + * calling this function with non-negative @flush_color. If + * @flush_color is negative, no flush color update is done and %false + * is returned. + * + * If @work_color is non-negative, all cwqs should have the same + * work_color which is previous to @work_color and all will be + * advanced to @work_color. + * + * CONTEXT: + * mutex_lock(wq->flush_mutex). + * + * RETURNS: + * %true if @flush_color >= 0 and there's something to flush. %false + * otherwise. + */ +static bool flush_workqueue_prep_cwqs(struct workqueue_struct *wq, + int flush_color, int work_color) { - int active = 0; - struct wq_barrier barr; + bool wait = false; + unsigned int cpu; - WARN_ON(cwq->thread == current); - - spin_lock_irq(&cwq->lock); - if (!list_empty(&cwq->worklist) || cwq->current_work != NULL) { - insert_wq_barrier(cwq, &barr, &cwq->worklist); - active = 1; + if (flush_color >= 0) { + BUG_ON(atomic_read(&wq->nr_cwqs_to_flush)); + atomic_set(&wq->nr_cwqs_to_flush, 1); } - spin_unlock_irq(&cwq->lock); - if (active) { - wait_for_completion(&barr.done); - destroy_work_on_stack(&barr.work); + for_each_possible_cpu(cpu) { + struct cpu_workqueue_struct *cwq = get_cwq(cpu, wq); + + spin_lock_irq(&cwq->lock); + + if (flush_color >= 0) { + BUG_ON(cwq->flush_color != -1); + + if (cwq->nr_in_flight[flush_color]) { + cwq->flush_color = flush_color; + atomic_inc(&wq->nr_cwqs_to_flush); + wait = true; + } + } + + if (work_color >= 0) { + BUG_ON(work_color != work_next_color(cwq->work_color)); + cwq->work_color = work_color; + } + + spin_unlock_irq(&cwq->lock); } - return active; + if (flush_color >= 0 && atomic_dec_and_test(&wq->nr_cwqs_to_flush)) + complete(&wq->first_flusher->done); + + return wait; } /** @@ -566,13 +698,143 @@ static int flush_cpu_workqueue(struct cpu_workqueue_struct *cwq) */ void flush_workqueue(struct workqueue_struct *wq) { - int cpu; + struct wq_flusher this_flusher = { + .list = LIST_HEAD_INIT(this_flusher.list), + .flush_color = -1, + .done = COMPLETION_INITIALIZER_ONSTACK(this_flusher.done), + }; + int next_color; - might_sleep(); lock_map_acquire(&wq->lockdep_map); lock_map_release(&wq->lockdep_map); - for_each_possible_cpu(cpu) - flush_cpu_workqueue(get_cwq(cpu, wq)); + + mutex_lock(&wq->flush_mutex); + + /* + * Start-to-wait phase + */ + next_color = work_next_color(wq->work_color); + + if (next_color != wq->flush_color) { + /* + * Color space is not full. The current work_color + * becomes our flush_color and work_color is advanced + * by one. + */ + BUG_ON(!list_empty(&wq->flusher_overflow)); + this_flusher.flush_color = wq->work_color; + wq->work_color = next_color; + + if (!wq->first_flusher) { + /* no flush in progress, become the first flusher */ + BUG_ON(wq->flush_color != this_flusher.flush_color); + + wq->first_flusher = &this_flusher; + + if (!flush_workqueue_prep_cwqs(wq, wq->flush_color, + wq->work_color)) { + /* nothing to flush, done */ + wq->flush_color = next_color; + wq->first_flusher = NULL; + goto out_unlock; + } + } else { + /* wait in queue */ + BUG_ON(wq->flush_color == this_flusher.flush_color); + list_add_tail(&this_flusher.list, &wq->flusher_queue); + flush_workqueue_prep_cwqs(wq, -1, wq->work_color); + } + } else { + /* + * Oops, color space is full, wait on overflow queue. + * The next flush completion will assign us + * flush_color and transfer to flusher_queue. + */ + list_add_tail(&this_flusher.list, &wq->flusher_overflow); + } + + mutex_unlock(&wq->flush_mutex); + + wait_for_completion(&this_flusher.done); + + /* + * Wake-up-and-cascade phase + * + * First flushers are responsible for cascading flushes and + * handling overflow. Non-first flushers can simply return. + */ + if (wq->first_flusher != &this_flusher) + return; + + mutex_lock(&wq->flush_mutex); + + wq->first_flusher = NULL; + + BUG_ON(!list_empty(&this_flusher.list)); + BUG_ON(wq->flush_color != this_flusher.flush_color); + + while (true) { + struct wq_flusher *next, *tmp; + + /* complete all the flushers sharing the current flush color */ + list_for_each_entry_safe(next, tmp, &wq->flusher_queue, list) { + if (next->flush_color != wq->flush_color) + break; + list_del_init(&next->list); + complete(&next->done); + } + + BUG_ON(!list_empty(&wq->flusher_overflow) && + wq->flush_color != work_next_color(wq->work_color)); + + /* this flush_color is finished, advance by one */ + wq->flush_color = work_next_color(wq->flush_color); + + /* one color has been freed, handle overflow queue */ + if (!list_empty(&wq->flusher_overflow)) { + /* + * Assign the same color to all overflowed + * flushers, advance work_color and append to + * flusher_queue. This is the start-to-wait + * phase for these overflowed flushers. + */ + list_for_each_entry(tmp, &wq->flusher_overflow, list) + tmp->flush_color = wq->work_color; + + wq->work_color = work_next_color(wq->work_color); + + list_splice_tail_init(&wq->flusher_overflow, + &wq->flusher_queue); + flush_workqueue_prep_cwqs(wq, -1, wq->work_color); + } + + if (list_empty(&wq->flusher_queue)) { + BUG_ON(wq->flush_color != wq->work_color); + break; + } + + /* + * Need to flush more colors. Make the next flusher + * the new first flusher and arm cwqs. + */ + BUG_ON(wq->flush_color == wq->work_color); + BUG_ON(wq->flush_color != next->flush_color); + + list_del_init(&next->list); + wq->first_flusher = next; + + if (flush_workqueue_prep_cwqs(wq, wq->flush_color, -1)) + break; + + /* + * Meh... this color is already done, clear first + * flusher and repeat cascading. + */ + wq->first_flusher = NULL; + } + +out_unlock: + mutex_unlock(&wq->flush_mutex); } EXPORT_SYMBOL_GPL(flush_workqueue); @@ -659,6 +921,7 @@ static int try_to_grab_pending(struct work_struct *work) if (cwq == get_wq_data(work)) { debug_work_deactivate(work); list_del_init(&work->entry); + cwq_dec_nr_in_flight(cwq, get_work_color(work)); ret = 1; } } @@ -1066,6 +1329,10 @@ struct workqueue_struct *__create_workqueue_key(const char *name, goto err; wq->flags = flags; + mutex_init(&wq->flush_mutex); + atomic_set(&wq->nr_cwqs_to_flush, 0); + INIT_LIST_HEAD(&wq->flusher_queue); + INIT_LIST_HEAD(&wq->flusher_overflow); wq->name = name; lockdep_init_map(&wq->lockdep_map, lock_name, key, 0); INIT_LIST_HEAD(&wq->list); @@ -1083,6 +1350,7 @@ struct workqueue_struct *__create_workqueue_key(const char *name, BUG_ON((unsigned long)cwq & WORK_STRUCT_FLAG_MASK); cwq->wq = wq; cwq->cpu = cpu; + cwq->flush_color = -1; spin_lock_init(&cwq->lock); INIT_LIST_HEAD(&cwq->worklist); init_waitqueue_head(&cwq->more_work); @@ -1116,33 +1384,6 @@ err: } EXPORT_SYMBOL_GPL(__create_workqueue_key); -static void cleanup_workqueue_thread(struct cpu_workqueue_struct *cwq) -{ - /* - * Our caller is either destroy_workqueue() or CPU_POST_DEAD, - * cpu_add_remove_lock protects cwq->thread. - */ - if (cwq->thread == NULL) - return; - - lock_map_acquire(&cwq->wq->lockdep_map); - lock_map_release(&cwq->wq->lockdep_map); - - flush_cpu_workqueue(cwq); - /* - * If the caller is CPU_POST_DEAD and cwq->worklist was not empty, - * a concurrent flush_workqueue() can insert a barrier after us. - * However, in that case run_workqueue() won't return and check - * kthread_should_stop() until it flushes all work_struct's. - * When ->worklist becomes empty it is safe to exit because no - * more work_structs can be queued on this cwq: flush_workqueue - * checks list_empty(), and a "normal" queue_work() can't use - * a dead CPU. - */ - kthread_stop(cwq->thread); - cwq->thread = NULL; -} - /** * destroy_workqueue - safely terminate a workqueue * @wq: target workqueue @@ -1159,8 +1400,20 @@ void destroy_workqueue(struct workqueue_struct *wq) spin_unlock(&workqueue_lock); cpu_maps_update_done(); - for_each_possible_cpu(cpu) - cleanup_workqueue_thread(get_cwq(cpu, wq)); + flush_workqueue(wq); + + for_each_possible_cpu(cpu) { + struct cpu_workqueue_struct *cwq = get_cwq(cpu, wq); + int i; + + if (cwq->thread) { + kthread_stop(cwq->thread); + cwq->thread = NULL; + } + + for (i = 0; i < WORK_NR_COLORS; i++) + BUG_ON(cwq->nr_in_flight[i]); + } free_cwqs(wq->cpu_wq); kfree(wq); @@ -1185,9 +1438,7 @@ static int __devinit workqueue_cpu_callback(struct notifier_block *nfb, switch (action) { case CPU_POST_DEAD: - lock_map_acquire(&cwq->wq->lockdep_map); - lock_map_release(&cwq->wq->lockdep_map); - flush_cpu_workqueue(cwq); + flush_workqueue(wq); break; } } |
