From 8d9df9f0844ed87541453a3ef91bfc9f487053b7 Mon Sep 17 00:00:00 2001 From: Xiaotian Feng Date: Mon, 16 Aug 2010 09:54:28 +0200 Subject: workqueue: free rescuer on destroy_workqueue wq->rescuer is not freed when wq is destroyed, leads a memory leak then. This patch also remove a redundant line. Signed-off-by: Xiaotian Feng Signed-off-by: Tejun Heo Cc: Oleg Nesterov diff --git a/kernel/workqueue.c b/kernel/workqueue.c index 2994a0e..1001b6e 100644 --- a/kernel/workqueue.c +++ b/kernel/workqueue.c @@ -2782,7 +2782,6 @@ struct workqueue_struct *__alloc_workqueue_key(const char *name, if (IS_ERR(rescuer->task)) goto err; - wq->rescuer = rescuer; rescuer->task->flags |= PF_THREAD_BOUND; wake_up_process(rescuer->task); } @@ -2848,6 +2847,7 @@ void destroy_workqueue(struct workqueue_struct *wq) if (wq->flags & WQ_RESCUER) { kthread_stop(wq->rescuer->task); free_mayday_mask(wq->mayday_mask); + kfree(wq->rescuer); } free_cwqs(wq); -- cgit v0.10.2 From 06bd6ebffae36d3b105677598c48e8bd0a10b205 Mon Sep 17 00:00:00 2001 From: Namhyung Kim Date: Sun, 22 Aug 2010 23:19:42 +0900 Subject: workqueue: annotate lock context change Some of internal functions called within gcwq->lock context releases and regrabs the lock but were missing proper annotations. Add it. Signed-off-by: Namhyung Kim Signed-off-by: Tejun Heo diff --git a/kernel/workqueue.c b/kernel/workqueue.c index 1001b6e..7415f27a 100644 --- a/kernel/workqueue.c +++ b/kernel/workqueue.c @@ -1485,6 +1485,8 @@ static void gcwq_mayday_timeout(unsigned long __gcwq) * otherwise. */ static bool maybe_create_worker(struct global_cwq *gcwq) +__releases(&gcwq->lock) +__acquires(&gcwq->lock) { if (!need_to_create_worker(gcwq)) return false; @@ -1722,6 +1724,8 @@ static void cwq_dec_nr_in_flight(struct cpu_workqueue_struct *cwq, int color) * spin_lock_irq(gcwq->lock) which is released and regrabbed. */ static void process_one_work(struct worker *worker, struct work_struct *work) +__releases(&gcwq->lock) +__acquires(&gcwq->lock) { struct cpu_workqueue_struct *cwq = get_work_cwq(work); struct global_cwq *gcwq = cwq->gcwq; @@ -3230,6 +3234,8 @@ static int __cpuinit trustee_thread(void *__gcwq) * multiple times. To be used by cpu_callback. */ static void __cpuinit wait_trustee_state(struct global_cwq *gcwq, int state) +__releases(&gcwq->lock) +__acquires(&gcwq->lock) { if (!(gcwq->trustee_state == state || gcwq->trustee_state == TRUSTEE_DONE)) { -- cgit v0.10.2 From 972fa1c5316d18c8297123e08e9b6930ca34f888 Mon Sep 17 00:00:00 2001 From: Namhyung Kim Date: Sun, 22 Aug 2010 23:19:43 +0900 Subject: workqueue: mark lock acquisition on worker_maybe_bind_and_lock() worker_maybe_bind_and_lock() actually grabs gcwq->lock but was missing proper annotation. Add it. So this patch will remove following sparse warnings: kernel/workqueue.c:1214:13: warning: context imbalance in 'worker_maybe_bind_and_lock' - wrong count at exit arch/x86/include/asm/irqflags.h:44:9: warning: context imbalance in 'worker_rebind_fn' - unexpected unlock kernel/workqueue.c:1991:17: warning: context imbalance in 'rescuer_thread' - unexpected unlock Signed-off-by: Namhyung Kim Signed-off-by: Tejun Heo diff --git a/kernel/workqueue.c b/kernel/workqueue.c index 7415f27a..cc3456f 100644 --- a/kernel/workqueue.c +++ b/kernel/workqueue.c @@ -1212,6 +1212,7 @@ static void worker_leave_idle(struct worker *worker) * bound), %false if offline. */ static bool worker_maybe_bind_and_lock(struct worker *worker) +__acquires(&gcwq->lock) { struct global_cwq *gcwq = worker->gcwq; struct task_struct *task = worker->task; -- cgit v0.10.2 From e41e704bc4f49057fc68b643108366e6e6781aa3 Mon Sep 17 00:00:00 2001 From: Tejun Heo Date: Tue, 24 Aug 2010 14:22:47 +0200 Subject: workqueue: improve destroy_workqueue() debuggability Now that the worklist is global, having works pending after wq destruction can easily lead to oops and destroy_workqueue() have several BUG_ON()s to catch these cases. Unfortunately, BUG_ON() doesn't tell much about how the work became pending after the final flush_workqueue(). This patch adds WQ_DYING which is set before the final flush begins. If a work is requested to be queued on a dying workqueue, WARN_ON_ONCE() is triggered and the request is ignored. This clearly indicates which caller is trying to queue a work on a dying workqueue and keeps the system working in most cases. Locking rule comment is updated such that the 'I' rule includes modifying the field from destruction path. Signed-off-by: Tejun Heo diff --git a/include/linux/workqueue.h b/include/linux/workqueue.h index 4f9d277..c959666 100644 --- a/include/linux/workqueue.h +++ b/include/linux/workqueue.h @@ -241,6 +241,8 @@ enum { WQ_HIGHPRI = 1 << 4, /* high priority */ WQ_CPU_INTENSIVE = 1 << 5, /* cpu instensive workqueue */ + WQ_DYING = 1 << 6, /* internal: workqueue is dying */ + WQ_MAX_ACTIVE = 512, /* I like 512, better ideas? */ WQ_MAX_UNBOUND_PER_CPU = 4, /* 4 * #cpus for unbound wq */ WQ_DFL_ACTIVE = WQ_MAX_ACTIVE / 2, diff --git a/kernel/workqueue.c b/kernel/workqueue.c index cc3456f..362b50d 100644 --- a/kernel/workqueue.c +++ b/kernel/workqueue.c @@ -87,7 +87,8 @@ enum { /* * Structure fields follow one of the following exclusion rules. * - * I: Set during initialization and read-only afterwards. + * I: Modifiable by initialization/destruction paths and read-only for + * everyone else. * * P: Preemption protected. Disabling preemption is enough and should * only be modified and accessed from the local cpu. @@ -944,6 +945,9 @@ static void __queue_work(unsigned int cpu, struct workqueue_struct *wq, debug_work_activate(work); + if (WARN_ON_ONCE(wq->flags & WQ_DYING)) + return; + /* determine gcwq to use */ if (!(wq->flags & WQ_UNBOUND)) { struct global_cwq *last_gcwq; @@ -2828,6 +2832,7 @@ void destroy_workqueue(struct workqueue_struct *wq) { unsigned int cpu; + wq->flags |= WQ_DYING; flush_workqueue(wq); /* -- cgit v0.10.2 From 8a2e8e5dec7e29c56a46ba176c664ab6a3d04118 Mon Sep 17 00:00:00 2001 From: Tejun Heo Date: Wed, 25 Aug 2010 10:33:56 +0200 Subject: workqueue: fix cwq->nr_active underflow cwq->nr_active is used to keep track of how many work items are active for the cpu workqueue, where 'active' is defined as either pending on global worklist or executing. This is used to implement the max_active limit and workqueue freezing. If a work item is queued after nr_active has already reached max_active, the work item doesn't increment nr_active and is put on the delayed queue and gets activated later as previous active work items retire. try_to_grab_pending() which is used in the cancellation path unconditionally decremented nr_active whether the work item being cancelled is currently active or delayed, so cancelling a delayed work item makes nr_active underflow. This breaks max_active enforcement and triggers BUG_ON() in destroy_workqueue() later on. This patch fixes this bug by adding a flag WORK_STRUCT_DELAYED, which is set while a work item in on the delayed list and making try_to_grab_pending() decrement nr_active iff the work item is currently active. The addition of the flag enlarges cwq alignment to 256 bytes which is getting a bit too large. It's scheduled to be reduced back to 128 bytes by merging WORK_STRUCT_PENDING and WORK_STRUCT_CWQ in the next devel cycle. Signed-off-by: Tejun Heo Reported-by: Johannes Berg diff --git a/include/linux/workqueue.h b/include/linux/workqueue.h index c959666..f11100f 100644 --- a/include/linux/workqueue.h +++ b/include/linux/workqueue.h @@ -25,18 +25,20 @@ typedef void (*work_func_t)(struct work_struct *work); enum { WORK_STRUCT_PENDING_BIT = 0, /* work item is pending execution */ - WORK_STRUCT_CWQ_BIT = 1, /* data points to cwq */ - WORK_STRUCT_LINKED_BIT = 2, /* next work is linked to this one */ + WORK_STRUCT_DELAYED_BIT = 1, /* work item is delayed */ + WORK_STRUCT_CWQ_BIT = 2, /* data points to cwq */ + WORK_STRUCT_LINKED_BIT = 3, /* next work is linked to this one */ #ifdef CONFIG_DEBUG_OBJECTS_WORK - WORK_STRUCT_STATIC_BIT = 3, /* static initializer (debugobjects) */ - WORK_STRUCT_COLOR_SHIFT = 4, /* color for workqueue flushing */ + WORK_STRUCT_STATIC_BIT = 4, /* static initializer (debugobjects) */ + WORK_STRUCT_COLOR_SHIFT = 5, /* color for workqueue flushing */ #else - WORK_STRUCT_COLOR_SHIFT = 3, /* color for workqueue flushing */ + WORK_STRUCT_COLOR_SHIFT = 4, /* color for workqueue flushing */ #endif WORK_STRUCT_COLOR_BITS = 4, WORK_STRUCT_PENDING = 1 << WORK_STRUCT_PENDING_BIT, + WORK_STRUCT_DELAYED = 1 << WORK_STRUCT_DELAYED_BIT, WORK_STRUCT_CWQ = 1 << WORK_STRUCT_CWQ_BIT, WORK_STRUCT_LINKED = 1 << WORK_STRUCT_LINKED_BIT, #ifdef CONFIG_DEBUG_OBJECTS_WORK @@ -59,8 +61,8 @@ enum { /* * Reserve 7 bits off of cwq pointer w/ debugobjects turned - * off. This makes cwqs aligned to 128 bytes which isn't too - * excessive while allowing 15 workqueue flush colors. + * off. This makes cwqs aligned to 256 bytes and allows 15 + * workqueue flush colors. */ WORK_STRUCT_FLAG_BITS = WORK_STRUCT_COLOR_SHIFT + WORK_STRUCT_COLOR_BITS, diff --git a/kernel/workqueue.c b/kernel/workqueue.c index 362b50d..a2dccfc 100644 --- a/kernel/workqueue.c +++ b/kernel/workqueue.c @@ -941,6 +941,7 @@ static void __queue_work(unsigned int cpu, struct workqueue_struct *wq, struct global_cwq *gcwq; struct cpu_workqueue_struct *cwq; struct list_head *worklist; + unsigned int work_flags; unsigned long flags; debug_work_activate(work); @@ -990,14 +991,17 @@ static void __queue_work(unsigned int cpu, struct workqueue_struct *wq, BUG_ON(!list_empty(&work->entry)); cwq->nr_in_flight[cwq->work_color]++; + work_flags = work_color_to_flags(cwq->work_color); if (likely(cwq->nr_active < cwq->max_active)) { cwq->nr_active++; worklist = gcwq_determine_ins_pos(gcwq, cwq); - } else + } else { + work_flags |= WORK_STRUCT_DELAYED; worklist = &cwq->delayed_works; + } - insert_work(cwq, work, worklist, work_color_to_flags(cwq->work_color)); + insert_work(cwq, work, worklist, work_flags); spin_unlock_irqrestore(&gcwq->lock, flags); } @@ -1666,6 +1670,7 @@ static void cwq_activate_first_delayed(struct cpu_workqueue_struct *cwq) struct list_head *pos = gcwq_determine_ins_pos(cwq->gcwq, cwq); move_linked_works(work, pos, NULL); + __clear_bit(WORK_STRUCT_DELAYED_BIT, work_data_bits(work)); cwq->nr_active++; } @@ -1673,6 +1678,7 @@ static void cwq_activate_first_delayed(struct cpu_workqueue_struct *cwq) * cwq_dec_nr_in_flight - decrement cwq's nr_in_flight * @cwq: cwq of interest * @color: color of work which left the queue + * @delayed: for a delayed work * * A work either has completed or is removed from pending queue, * decrement nr_in_flight of its cwq and handle workqueue flushing. @@ -1680,19 +1686,22 @@ static void cwq_activate_first_delayed(struct cpu_workqueue_struct *cwq) * CONTEXT: * spin_lock_irq(gcwq->lock). */ -static void cwq_dec_nr_in_flight(struct cpu_workqueue_struct *cwq, int color) +static void cwq_dec_nr_in_flight(struct cpu_workqueue_struct *cwq, int color, + bool delayed) { /* ignore uncolored works */ if (color == WORK_NO_COLOR) return; cwq->nr_in_flight[color]--; - cwq->nr_active--; - if (!list_empty(&cwq->delayed_works)) { - /* one down, submit a delayed one */ - if (cwq->nr_active < cwq->max_active) - cwq_activate_first_delayed(cwq); + if (!delayed) { + cwq->nr_active--; + if (!list_empty(&cwq->delayed_works)) { + /* one down, submit a delayed one */ + if (cwq->nr_active < cwq->max_active) + cwq_activate_first_delayed(cwq); + } } /* is flush in progress and are we at the flushing tip? */ @@ -1823,7 +1832,7 @@ __acquires(&gcwq->lock) hlist_del_init(&worker->hentry); worker->current_work = NULL; worker->current_cwq = NULL; - cwq_dec_nr_in_flight(cwq, work_color); + cwq_dec_nr_in_flight(cwq, work_color, false); } /** @@ -2388,7 +2397,8 @@ static int try_to_grab_pending(struct work_struct *work) debug_work_deactivate(work); list_del_init(&work->entry); cwq_dec_nr_in_flight(get_work_cwq(work), - get_work_color(work)); + get_work_color(work), + *work_data_bits(work) & WORK_STRUCT_DELAYED); ret = 1; } } -- cgit v0.10.2 From 7c38875a0d0a9b90eee66be79e36995c86acc70c Mon Sep 17 00:00:00 2001 From: Jason Baron Date: Thu, 26 Aug 2010 10:35:43 -0400 Subject: workqueue: Add a workqueue chapter to the tracepoint docbook Add a workqueue chapter to the traceopint docbook. Current book is at: http://www.kernel.org/doc/htmldocs/tracepoint/ Signed-off-by: Jason Baron Signed-off-by: Tejun Heo diff --git a/Documentation/DocBook/tracepoint.tmpl b/Documentation/DocBook/tracepoint.tmpl index e8473ea..b57a9ed 100644 --- a/Documentation/DocBook/tracepoint.tmpl +++ b/Documentation/DocBook/tracepoint.tmpl @@ -104,4 +104,9 @@ Block IO !Iinclude/trace/events/block.h + + + Workqueue +!Iinclude/trace/events/workqueue.h + -- cgit v0.10.2 From 477a3c33d1efa0342a74bd02da2e049191993e2c Mon Sep 17 00:00:00 2001 From: Tejun Heo Date: Tue, 31 Aug 2010 10:54:35 +0200 Subject: workqueue: fix GCWQ_DISASSOCIATED initialization init_workqueues() incorrectly marks workqueues for all possible CPUs associated. Combined with mayday_mask initialization bug, this can make rescuers keep trying to bind to an offline gcwq indefinitely. Fix init_workqueues() such that only online CPUs have their gcwqs have GCWQ_DISASSOCIATED cleared. Signed-off-by: Tejun Heo Reported-by: CAI Qian diff --git a/kernel/workqueue.c b/kernel/workqueue.c index a2dccfc..c8183b2 100644 --- a/kernel/workqueue.c +++ b/kernel/workqueue.c @@ -3558,8 +3558,7 @@ static int __init init_workqueues(void) spin_lock_init(&gcwq->lock); INIT_LIST_HEAD(&gcwq->worklist); gcwq->cpu = cpu; - if (cpu == WORK_CPU_UNBOUND) - gcwq->flags |= GCWQ_DISASSOCIATED; + gcwq->flags |= GCWQ_DISASSOCIATED; INIT_LIST_HEAD(&gcwq->idle_list); for (i = 0; i < BUSY_WORKER_HASH_SIZE; i++) @@ -3583,6 +3582,8 @@ static int __init init_workqueues(void) struct global_cwq *gcwq = get_gcwq(cpu); struct worker *worker; + if (cpu != WORK_CPU_UNBOUND) + gcwq->flags &= ~GCWQ_DISASSOCIATED; worker = create_worker(gcwq, true); BUG_ON(!worker); spin_lock_irq(&gcwq->lock); -- cgit v0.10.2 From 9c37547ab62f88aac3e1e3c2065b611f811de9b5 Mon Sep 17 00:00:00 2001 From: Tejun Heo Date: Tue, 31 Aug 2010 11:18:34 +0200 Subject: workqueue: use zalloc_cpumask_var() for gcwq->mayday_mask alloc_mayday_mask() was using alloc_cpumask_var() making gcwq->mayday_mask contain garbage after initialization on CONFIG_CPUMASK_OFFSTACK=y configurations. This combined with the previously fixed GCWQ_DISASSOCIATED initialization bug could make rescuers fall into infinite loop trying to bind to an offline cpu. Signed-off-by: Tejun Heo Reported-by: CAI Qian diff --git a/kernel/workqueue.c b/kernel/workqueue.c index c8183b2..7855429 100644 --- a/kernel/workqueue.c +++ b/kernel/workqueue.c @@ -196,7 +196,7 @@ typedef cpumask_var_t mayday_mask_t; cpumask_test_and_set_cpu((cpu), (mask)) #define mayday_clear_cpu(cpu, mask) cpumask_clear_cpu((cpu), (mask)) #define for_each_mayday_cpu(cpu, mask) for_each_cpu((cpu), (mask)) -#define alloc_mayday_mask(maskp, gfp) alloc_cpumask_var((maskp), (gfp)) +#define alloc_mayday_mask(maskp, gfp) zalloc_cpumask_var((maskp), (gfp)) #define free_mayday_mask(mask) free_cpumask_var((mask)) #else typedef unsigned long mayday_mask_t; -- cgit v0.10.2