From bdbc5dd7de5d07d6c9d3536e598956165a031d4c Mon Sep 17 00:00:00 2001 From: Tejun Heo Date: Fri, 2 Jul 2010 10:03:51 +0200 Subject: [PATCH] workqueue: prepare for WQ_UNBOUND implementation In preparation of WQ_UNBOUND addition, make the following changes. * Add WORK_CPU_* constants for pseudo cpu id numbers used (currently only WORK_CPU_NONE) and use them instead of NR_CPUS. This is to allow another pseudo cpu id for unbound cpu. * Reorder WQ_* flags. * Make workqueue_struct->cpu_wq a union which contains a percpu pointer, regular pointer and an unsigned long value and use kzalloc/kfree() in UP allocation path. This will be used to implement unbound workqueues which will use only one cwq on SMPs. * Move alloc_cwqs() allocation after initialization of wq fields, so that alloc_cwqs() has access to wq->flags. * Trivial relocation of wq local variables in freeze functions. These changes don't cause any functional change. Signed-off-by: Tejun Heo --- include/linux/workqueue.h | 10 +++-- kernel/workqueue.c | 83 ++++++++++++++++++++------------------- 2 files changed, 50 insertions(+), 43 deletions(-) diff --git a/include/linux/workqueue.h b/include/linux/workqueue.h index 3f36d37ac5ba..139069a6286c 100644 --- a/include/linux/workqueue.h +++ b/include/linux/workqueue.h @@ -50,6 +50,10 @@ enum { WORK_NR_COLORS = (1 << WORK_STRUCT_COLOR_BITS) - 1, WORK_NO_COLOR = WORK_NR_COLORS, + /* special cpu IDs */ + WORK_CPU_NONE = NR_CPUS, + WORK_CPU_LAST = WORK_CPU_NONE, + /* * Reserve 6 bits off of cwq pointer w/ debugobjects turned * off. This makes cwqs aligned to 64 bytes which isn't too @@ -60,7 +64,7 @@ enum { WORK_STRUCT_FLAG_MASK = (1UL << WORK_STRUCT_FLAG_BITS) - 1, WORK_STRUCT_WQ_DATA_MASK = ~WORK_STRUCT_FLAG_MASK, - WORK_STRUCT_NO_CPU = NR_CPUS << WORK_STRUCT_FLAG_BITS, + WORK_STRUCT_NO_CPU = WORK_CPU_NONE << WORK_STRUCT_FLAG_BITS, /* bit mask for work_busy() return values */ WORK_BUSY_PENDING = 1 << 0, @@ -227,9 +231,9 @@ static inline unsigned int work_static(struct work_struct *work) { return 0; } clear_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(work)) enum { - WQ_FREEZEABLE = 1 << 0, /* freeze during suspend */ + WQ_NON_REENTRANT = 1 << 0, /* guarantee non-reentrance */ WQ_SINGLE_CPU = 1 << 1, /* only single cpu at a time */ - WQ_NON_REENTRANT = 1 << 2, /* guarantee non-reentrance */ + WQ_FREEZEABLE = 1 << 2, /* freeze during suspend */ WQ_RESCUER = 1 << 3, /* has an rescue worker */ WQ_HIGHPRI = 1 << 4, /* high priority */ WQ_CPU_INTENSIVE = 1 << 5, /* cpu instensive workqueue */ diff --git a/kernel/workqueue.c b/kernel/workqueue.c index 2eb9fbddf5c6..a105ddf55f79 100644 --- a/kernel/workqueue.c +++ b/kernel/workqueue.c @@ -190,7 +190,11 @@ struct wq_flusher { */ struct workqueue_struct { unsigned int flags; /* I: WQ_* flags */ - struct cpu_workqueue_struct *cpu_wq; /* I: cwq's */ + union { + struct cpu_workqueue_struct __percpu *pcpu; + struct cpu_workqueue_struct *single; + unsigned long v; + } cpu_wq; /* I: cwq's */ struct list_head list; /* W: list of all workqueues */ struct mutex flush_mutex; /* protects wq flushing */ @@ -362,7 +366,11 @@ static atomic_t *get_gcwq_nr_running(unsigned int cpu) static struct cpu_workqueue_struct *get_cwq(unsigned int cpu, struct workqueue_struct *wq) { - return per_cpu_ptr(wq->cpu_wq, cpu); +#ifndef CONFIG_SMP + return wq->cpu_wq.single; +#else + return per_cpu_ptr(wq->cpu_wq.pcpu, cpu); +#endif } static unsigned int work_color_to_flags(int color) @@ -442,7 +450,7 @@ static struct global_cwq *get_work_gcwq(struct work_struct *work) return ((struct cpu_workqueue_struct *)data)->gcwq; cpu = data >> WORK_STRUCT_FLAG_BITS; - if (cpu == NR_CPUS) + if (cpu == WORK_CPU_NONE) return NULL; BUG_ON(cpu >= nr_cpu_ids); @@ -846,7 +854,7 @@ static void cwq_unbind_single_cpu(struct cpu_workqueue_struct *cwq) */ if (likely(!(gcwq->flags & GCWQ_FREEZING))) { smp_wmb(); /* paired with cmpxchg() in __queue_work() */ - wq->single_cpu = NR_CPUS; + wq->single_cpu = WORK_CPU_NONE; } } @@ -904,7 +912,7 @@ static void __queue_work(unsigned int cpu, struct workqueue_struct *wq, */ retry: cpu = wq->single_cpu; - arbitrate = cpu == NR_CPUS; + arbitrate = cpu == WORK_CPU_NONE; if (arbitrate) cpu = req_cpu; @@ -918,7 +926,7 @@ static void __queue_work(unsigned int cpu, struct workqueue_struct *wq, * visible on the new cpu after this point. */ if (arbitrate) - cmpxchg(&wq->single_cpu, NR_CPUS, cpu); + cmpxchg(&wq->single_cpu, WORK_CPU_NONE, cpu); if (unlikely(wq->single_cpu != cpu)) { spin_unlock_irqrestore(&gcwq->lock, flags); @@ -2572,7 +2580,7 @@ int keventd_up(void) return system_wq != NULL; } -static struct cpu_workqueue_struct *alloc_cwqs(void) +static int alloc_cwqs(struct workqueue_struct *wq) { /* * cwqs are forced aligned according to WORK_STRUCT_FLAG_BITS. @@ -2582,40 +2590,36 @@ static struct cpu_workqueue_struct *alloc_cwqs(void) const size_t size = sizeof(struct cpu_workqueue_struct); const size_t align = max_t(size_t, 1 << WORK_STRUCT_FLAG_BITS, __alignof__(unsigned long long)); - struct cpu_workqueue_struct *cwqs; #ifndef CONFIG_SMP void *ptr; /* - * On UP, percpu allocator doesn't honor alignment parameter - * and simply uses arch-dependent default. Allocate enough - * room to align cwq and put an extra pointer at the end - * pointing back to the originally allocated pointer which - * will be used for free. - * - * FIXME: This really belongs to UP percpu code. Update UP - * percpu code to honor alignment and remove this ugliness. + * Allocate enough room to align cwq and put an extra pointer + * at the end pointing back to the originally allocated + * pointer which will be used for free. */ - ptr = __alloc_percpu(size + align + sizeof(void *), 1); - cwqs = PTR_ALIGN(ptr, align); - *(void **)per_cpu_ptr(cwqs + 1, 0) = ptr; + ptr = kzalloc(size + align + sizeof(void *), GFP_KERNEL); + if (ptr) { + wq->cpu_wq.single = PTR_ALIGN(ptr, align); + *(void **)(wq->cpu_wq.single + 1) = ptr; + } #else - /* On SMP, percpu allocator can do it itself */ - cwqs = __alloc_percpu(size, align); + /* On SMP, percpu allocator can align itself */ + wq->cpu_wq.pcpu = __alloc_percpu(size, align); #endif /* just in case, make sure it's actually aligned */ - BUG_ON(!IS_ALIGNED((unsigned long)cwqs, align)); - return cwqs; + BUG_ON(!IS_ALIGNED(wq->cpu_wq.v, align)); + return wq->cpu_wq.v ? 0 : -ENOMEM; } -static void free_cwqs(struct cpu_workqueue_struct *cwqs) +static void free_cwqs(struct workqueue_struct *wq) { #ifndef CONFIG_SMP /* on UP, the pointer to free is stored right after the cwq */ - if (cwqs) - free_percpu(*(void **)per_cpu_ptr(cwqs + 1, 0)); + if (wq->cpu_wq.single) + kfree(*(void **)(wq->cpu_wq.single + 1)); #else - free_percpu(cwqs); + free_percpu(wq->cpu_wq.pcpu); #endif } @@ -2645,22 +2649,21 @@ struct workqueue_struct *__alloc_workqueue_key(const char *name, if (!wq) goto err; - wq->cpu_wq = alloc_cwqs(); - if (!wq->cpu_wq) - goto err; - wq->flags = flags; wq->saved_max_active = max_active; 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->single_cpu = NR_CPUS; + wq->single_cpu = WORK_CPU_NONE; wq->name = name; lockdep_init_map(&wq->lockdep_map, lock_name, key, 0); INIT_LIST_HEAD(&wq->list); + if (alloc_cwqs(wq) < 0) + goto err; + for_each_possible_cpu(cpu) { struct cpu_workqueue_struct *cwq = get_cwq(cpu, wq); struct global_cwq *gcwq = get_gcwq(cpu); @@ -2710,7 +2713,7 @@ struct workqueue_struct *__alloc_workqueue_key(const char *name, return wq; err: if (wq) { - free_cwqs(wq->cpu_wq); + free_cwqs(wq); free_cpumask_var(wq->mayday_mask); kfree(wq->rescuer); kfree(wq); @@ -2755,7 +2758,7 @@ void destroy_workqueue(struct workqueue_struct *wq) free_cpumask_var(wq->mayday_mask); } - free_cwqs(wq->cpu_wq); + free_cwqs(wq); kfree(wq); } EXPORT_SYMBOL_GPL(destroy_workqueue); @@ -2821,13 +2824,13 @@ EXPORT_SYMBOL_GPL(workqueue_congested); * @work: the work of interest * * RETURNS: - * CPU number if @work was ever queued. NR_CPUS otherwise. + * CPU number if @work was ever queued. WORK_CPU_NONE otherwise. */ unsigned int work_cpu(struct work_struct *work) { struct global_cwq *gcwq = get_work_gcwq(work); - return gcwq ? gcwq->cpu : NR_CPUS; + return gcwq ? gcwq->cpu : WORK_CPU_NONE; } EXPORT_SYMBOL_GPL(work_cpu); @@ -3300,7 +3303,6 @@ EXPORT_SYMBOL_GPL(work_on_cpu); */ void freeze_workqueues_begin(void) { - struct workqueue_struct *wq; unsigned int cpu; spin_lock(&workqueue_lock); @@ -3310,6 +3312,7 @@ void freeze_workqueues_begin(void) for_each_possible_cpu(cpu) { struct global_cwq *gcwq = get_gcwq(cpu); + struct workqueue_struct *wq; spin_lock_irq(&gcwq->lock); @@ -3344,7 +3347,6 @@ void freeze_workqueues_begin(void) */ bool freeze_workqueues_busy(void) { - struct workqueue_struct *wq; unsigned int cpu; bool busy = false; @@ -3353,6 +3355,7 @@ bool freeze_workqueues_busy(void) BUG_ON(!workqueue_freezing); for_each_possible_cpu(cpu) { + struct workqueue_struct *wq; /* * nr_active is monotonically decreasing. It's safe * to peek without lock. @@ -3386,7 +3389,6 @@ bool freeze_workqueues_busy(void) */ void thaw_workqueues(void) { - struct workqueue_struct *wq; unsigned int cpu; spin_lock(&workqueue_lock); @@ -3396,6 +3398,7 @@ void thaw_workqueues(void) for_each_possible_cpu(cpu) { struct global_cwq *gcwq = get_gcwq(cpu); + struct workqueue_struct *wq; spin_lock_irq(&gcwq->lock); @@ -3443,7 +3446,7 @@ void __init init_workqueues(void) * sure cpu number won't overflow into kernel pointer area so * that they can be distinguished. */ - BUILD_BUG_ON(NR_CPUS << WORK_STRUCT_FLAG_BITS >= PAGE_OFFSET); + BUILD_BUG_ON(WORK_CPU_LAST << WORK_STRUCT_FLAG_BITS >= PAGE_OFFSET); hotcpu_notifier(workqueue_cpu_callback, CPU_PRI_WORKQUEUE); -- GitLab