Make workqueue bit operations work on "atomic_long_t"

On architectures where the atomicity of the bit operations is handled by external means (ie a separate spinlock to protect concurrent accesses), just doing a direct assignment on the workqueue data field (as done by commit 4594bf159f1962cec3b727954b7c598b07e2e737) can cause the assignment to be lost due to lack of serialization with the bitops on the same word. So we need to serialize the assignment with the locks on those architectures (notably older ARM chips, PA-RISC and sparc32). So rather than using an "unsigned long", let's use "atomic_long_t", which already has a safe assignment operation (atomic_long_set()) on such architectures. This requires that the atomic operations use the same atomicity locks as the bit operations do, but that is largely the case anyway. Sparc32 will probably need fixing. Architectures (including modern ARM with LL/SC) that implement sane atomic operations for SMP won't see any of this matter.

Linus Torvalds committed 19 years ago

Commit a08727b1 parent 2f77d102 files · +30 −18Browse files

Showing the changes to kernel/workqueue.c (1 of 2 files). Show all

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kernel/workqueue.c+8−8

@@ -96,13 +96,13 @@ static inline void set_wq_data(struct work_struct work, void wq) · 95 unmodified lines
96	96	BUG_ON(!work_pending(work));
97	97
98	98	new = (unsigned long) wq \| (1UL << WORK_STRUCT_PENDING);
99		− new \|= work->management & WORK_STRUCT_FLAG_MASK;
100		− work->management = new;
	99	+ new \|= WORK_STRUCT_FLAG_MASK & *work_data_bits(work);
	100	+ atomic_long_set(&work->data, new);
101	101	}
102	102
103	103	static inline void get_wq_data(struct work_struct work)
104	104	{
105		− return (void *) (work->management & WORK_STRUCT_WQ_DATA_MASK);
	105	+ return (void *) (atomic_long_read(&work->data) & WORK_STRUCT_WQ_DATA_MASK);
106	106	}
107	107
108	108	static int __run_work(struct cpu_workqueue_struct cwq, struct work_struct work)
@@ -133,7 +133,7 @@ static int __run_work(struct cpu_workqueue_struct cwq, struct work_struct work · 24 unmodified lines
133	133	list_del_init(&work->entry);
134	134	spin_unlock_irqrestore(&cwq->lock, flags);
135	135
136		− if (!test_bit(WORK_STRUCT_NOAUTOREL, &work->management))
	136	+ if (!test_bit(WORK_STRUCT_NOAUTOREL, work_data_bits(work)))
137	137	work_release(work);
138	138	f(work);
139	139
@@ -206,7 +206,7 @@ int fastcall queue_work(struct workqueue_struct wq, struct work_struct work) · 66 unmodified lines
206	206	{
207	207	int ret = 0, cpu = get_cpu();
208	208
209		− if (!test_and_set_bit(WORK_STRUCT_PENDING, &work->management)) {
	209	+ if (!test_and_set_bit(WORK_STRUCT_PENDING, work_data_bits(work))) {
210	210	if (unlikely(is_single_threaded(wq)))
211	211	cpu = singlethread_cpu;
212	212	BUG_ON(!list_empty(&work->entry));
@@ -248,7 +248,7 @@ int fastcall queue_delayed_work(struct workqueue_struct *wq, · 35 unmodified lines
248	248	if (delay == 0)
249	249	return queue_work(wq, work);
250	250
251		− if (!test_and_set_bit(WORK_STRUCT_PENDING, &work->management)) {
	251	+ if (!test_and_set_bit(WORK_STRUCT_PENDING, work_data_bits(work))) {
252	252	BUG_ON(timer_pending(timer));
253	253	BUG_ON(!list_empty(&work->entry));
254	254
@@ -280,7 +280,7 @@ int queue_delayed_work_on(int cpu, struct workqueue_struct *wq, · 25 unmodified lines
280	280	struct timer_list *timer = &dwork->timer;
281	281	struct work_struct *work = &dwork->work;
282	282
283		− if (!test_and_set_bit(WORK_STRUCT_PENDING, &work->management)) {
	283	+ if (!test_and_set_bit(WORK_STRUCT_PENDING, work_data_bits(work))) {
284	284	BUG_ON(timer_pending(timer));
285	285	BUG_ON(!list_empty(&work->entry));
286	286
@@ -321,7 +321,7 @@ static void run_workqueue(struct cpu_workqueue_struct *cwq) · 34 unmodified lines
321	321	spin_unlock_irqrestore(&cwq->lock, flags);
322	322
323	323	BUG_ON(get_wq_data(work) != cwq);
324		− if (!test_bit(WORK_STRUCT_NOAUTOREL, &work->management))
	324	+ if (!test_bit(WORK_STRUCT_NOAUTOREL, work_data_bits(work)))
325	325	work_release(work);
326	326	f(work);
327	327