And here is the diff which brings things up to 2.5.74. It's a tad
inelegant in shed.c:__wake_up_common(), but from my perspective I wanted
to keep the existing code there as simple as possible, to ease future
(2.4.22+) porting.
Any comments/advice appreciated, thanks.
/fc
diff -uNrp linux-2.4.21-wq.51/include/linux/wait.h linux-2.4.21-wq.74/include/linux/wait.h
--- linux-2.4.21-wq.51/include/linux/wait.h Tue Jul 8 01:45:04 2003
+++ linux-2.4.21-wq.74/include/linux/wait.h Tue Jul 8 02:24:17 2003
@@ -28,17 +28,21 @@
#define WAITQUEUE_DEBUG 0
#endif
+typedef struct __wait_queue wait_queue_t;
+typedef int (*wait_queue_func_t)(wait_queue_t *wait, unsigned mode, int sync);
+extern int default_wake_function(wait_queue_t *wait, unsigned mode, int sync);
+
struct __wait_queue {
unsigned int flags;
#define WQ_FLAG_EXCLUSIVE 0x01
struct task_struct * task;
+ wait_queue_func_t func;
struct list_head task_list;
#if WAITQUEUE_DEBUG
long __magic;
long __waker;
#endif
};
-typedef struct __wait_queue wait_queue_t;
/*
* 'dual' spinlock architecture. Can be switched between spinlock_t and
@@ -174,6 +178,7 @@ static inline void init_waitqueue_entry(
#endif
q->flags = 0;
q->task = p;
+ q->func = NULL;
#if WAITQUEUE_DEBUG
q->__magic = (long)&q->__magic;
#endif
@@ -230,6 +235,25 @@ static inline void __remove_wait_queue(w
#endif
list_del(&old->task_list);
}
+
+/*
+ * Waitqueues which are removed from the waitqueue_head at wakeup time
+ */
+void FASTCALL(prepare_to_wait(wait_queue_head_t *q,
+ wait_queue_t *wait, int state));
+void FASTCALL(prepare_to_wait_exclusive(wait_queue_head_t *q,
+ wait_queue_t *wait, int state));
+void FASTCALL(finish_wait(wait_queue_head_t *q, wait_queue_t *wait));
+int autoremove_wake_function(wait_queue_t *wait, unsigned mode, int sync);
+
+#define DEFINE_WAIT(name) \
+ wait_queue_t name = { \
+ .task = current, \
+ .func = autoremove_wake_function, \
+ .task_list = { .next = &name.task_list, \
+ .prev = &name.task_list, \
+ }, \
+ }
#endif /* __KERNEL__ */
diff -uNrp linux-2.4.21-wq.51/kernel/fork.c linux-2.4.21-wq.74/kernel/fork.c
--- linux-2.4.21-wq.51/kernel/fork.c Tue Jul 8 01:45:04 2003
+++ linux-2.4.21-wq.74/kernel/fork.c Tue Jul 8 02:24:28 2003
@@ -68,6 +68,52 @@ void remove_wait_queue(wait_queue_head_t
wq_write_unlock_irqrestore(&q->lock, flags);
}
+void prepare_to_wait(wait_queue_head_t *q, wait_queue_t *wait, int state)
+{
+ unsigned long flags;
+
+ __set_current_state(state);
+ wait->flags &= ~WQ_FLAG_EXCLUSIVE;
+ spin_lock_irqsave(&q->lock, flags);
+ if (list_empty(&wait->task_list))
+ __add_wait_queue(q, wait);
+ spin_unlock_irqrestore(&q->lock, flags);
+}
+
+void
+prepare_to_wait_exclusive(wait_queue_head_t *q, wait_queue_t *wait, int state)
+{
+ unsigned long flags;
+
+ __set_current_state(state);
+ wait->flags |= WQ_FLAG_EXCLUSIVE;
+ spin_lock_irqsave(&q->lock, flags);
+ if (list_empty(&wait->task_list))
+ __add_wait_queue_tail(q, wait);
+ spin_unlock_irqrestore(&q->lock, flags);
+}
+
+void finish_wait(wait_queue_head_t *q, wait_queue_t *wait)
+{
+ unsigned long flags;
+
+ __set_current_state(TASK_RUNNING);
+ if (!list_empty(&wait->task_list)) {
+ spin_lock_irqsave(&q->lock, flags);
+ list_del_init(&wait->task_list);
+ spin_unlock_irqrestore(&q->lock, flags);
+ }
+}
+
+int autoremove_wake_function(wait_queue_t *wait, unsigned mode, int sync)
+{
+ int ret = default_wake_function(wait, mode, sync);
+
+ if (ret)
+ list_del_init(&wait->task_list);
+ return ret;
+}
+
void __init fork_init(unsigned long mempages)
{
/*
diff -uNrp linux-2.4.21-wq.51/kernel/ksyms.c linux-2.4.21-wq.74/kernel/ksyms.c
--- linux-2.4.21-wq.51/kernel/ksyms.c Tue Jul 8 01:45:04 2003
+++ linux-2.4.21-wq.74/kernel/ksyms.c Tue Jul 8 02:35:38 2003
@@ -378,6 +378,10 @@ EXPORT_SYMBOL(irq_stat);
EXPORT_SYMBOL(add_wait_queue);
EXPORT_SYMBOL(add_wait_queue_exclusive);
EXPORT_SYMBOL(remove_wait_queue);
+EXPORT_SYMBOL(prepare_to_wait);
+EXPORT_SYMBOL(prepare_to_wait_exclusive);
+EXPORT_SYMBOL(finish_wait);
+EXPORT_SYMBOL(autoremove_wake_function);
/* completion handling */
EXPORT_SYMBOL(wait_for_completion);
@@ -444,6 +448,7 @@ EXPORT_SYMBOL(iomem_resource);
/* process management */
EXPORT_SYMBOL(complete_and_exit);
+EXPORT_SYMBOL(default_wake_function);
EXPORT_SYMBOL(__wake_up);
EXPORT_SYMBOL(__wake_up_sync);
EXPORT_SYMBOL(wake_up_process);
diff -uNrp linux-2.4.21-wq.51/kernel/sched.c linux-2.4.21-wq.74/kernel/sched.c
--- linux-2.4.21-wq.51/kernel/sched.c Tue Jul 8 01:45:04 2003
+++ linux-2.4.21-wq.74/kernel/sched.c Tue Jul 8 02:24:43 2003
@@ -702,6 +702,12 @@ same_process:
return;
}
+int default_wake_function(wait_queue_t *curr, unsigned mode, int sync)
+{
+ struct task_struct *p = curr->task;
+ return try_to_wake_up(p, sync);
+}
+
/*
* The core wakeup function. Non-exclusive wakeups (nr_exclusive == 0) just wake everything
* up. If it's an exclusive wakeup (nr_exclusive == small +ve number) then we wake all the
@@ -714,22 +720,29 @@ same_process:
static inline void __wake_up_common (wait_queue_head_t *q, unsigned int mode,
int nr_exclusive, const int sync)
{
- struct list_head *tmp;
+ struct list_head *tmp, *next;
struct task_struct *p;
CHECK_MAGIC_WQHEAD(q);
WQ_CHECK_LIST_HEAD(&q->task_list);
- list_for_each(tmp,&q->task_list) {
+ list_for_each_safe(tmp, next, &q->task_list) {
unsigned int state;
+ unsigned flags;
wait_queue_t *curr = list_entry(tmp, wait_queue_t, task_list);
CHECK_MAGIC(curr->__magic);
+ flags = curr->flags;
p = curr->task;
state = p->state;
if (state & mode) {
+ int r;
WQ_NOTE_WAKER(curr);
- if (try_to_wake_up(p, sync) && (curr->flags&WQ_FLAG_EXCLUSIVE) && !--nr_exclusive)
+ if (curr->func)
+ r = curr->func(curr, mode, sync);
+ else
+ r = try_to_wake_up(p, sync);
+ if (r && (flags&WQ_FLAG_EXCLUSIVE) && !--nr_exclusive)
break;
}
}
diff -uNrp linux-2.4.21-wq.51/kernel/workqueue.c linux-2.4.21-wq.74/kernel/workqueue.c
--- linux-2.4.21-wq.51/kernel/workqueue.c Tue Jul 8 01:50:31 2003
+++ linux-2.4.21-wq.74/kernel/workqueue.c Tue Jul 8 02:24:49 2003
@@ -27,13 +27,21 @@
#include <linux/slab.h>
/*
- * The per-CPU workqueue:
+ * The per-CPU workqueue.
+ *
+ * The sequence counters are for flush_scheduled_work(). It wants to wait
+ * until until all currently-scheduled works are completed, but it doesn't
+ * want to be livelocked by new, incoming ones. So it waits until
+ * remove_sequence is >= the insert_sequence which pertained when
+ * flush_scheduled_work() was called.
*/
struct cpu_workqueue_struct {
spinlock_t lock;
- atomic_t nr_queued;
+ long remove_sequence; /* Least-recently added (next to run) */
+ long insert_sequence; /* Next to add */
+
struct list_head worklist;
wait_queue_head_t more_work;
wait_queue_head_t work_done;
@@ -71,10 +79,9 @@ int queue_work(struct workqueue_struct *
spin_lock_irqsave(&cwq->lock, flags);
list_add_tail(&work->entry, &cwq->worklist);
- atomic_inc(&cwq->nr_queued);
- spin_unlock_irqrestore(&cwq->lock, flags);
-
+ cwq->insert_sequence++;
wake_up(&cwq->more_work);
+ spin_unlock_irqrestore(&cwq->lock, flags);
ret = 1;
}
return ret;
@@ -92,11 +99,13 @@ static void delayed_work_timer_fn(unsign
*/
spin_lock_irqsave(&cwq->lock, flags);
list_add_tail(&work->entry, &cwq->worklist);
+ cwq->insert_sequence++;
wake_up(&cwq->more_work);
spin_unlock_irqrestore(&cwq->lock, flags);
}
-int queue_delayed_work(struct workqueue_struct *wq, struct work_struct *work, unsigned long delay)
+int queue_delayed_work(struct workqueue_struct *wq,
+ struct work_struct *work, unsigned long delay)
{
int ret = 0, cpu = smp_processor_id();
struct timer_list *timer = &work->timer;
@@ -106,18 +115,11 @@ int queue_delayed_work(struct workqueue_
BUG_ON(timer_pending(timer));
BUG_ON(!list_empty(&work->entry));
- /*
- * Increase nr_queued so that the flush function
- * knows that there's something pending.
- */
- atomic_inc(&cwq->nr_queued);
work->wq_data = cwq;
-
timer->expires = jiffies + delay;
timer->data = (unsigned long)work;
timer->function = delayed_work_timer_fn;
add_timer(timer);
-
ret = 1;
}
return ret;
@@ -133,7 +135,8 @@ static inline void run_workqueue(struct
*/
spin_lock_irqsave(&cwq->lock, flags);
while (!list_empty(&cwq->worklist)) {
- struct work_struct *work = list_entry(cwq->worklist.next, struct work_struct, entry);
+ struct work_struct *work = list_entry(cwq->worklist.next,
+ struct work_struct, entry);
void (*f) (void *) = work->func;
void *data = work->data;
@@ -144,14 +147,9 @@ static inline void run_workqueue(struct
clear_bit(0, &work->pending);
f(data);
- /*
- * We only wake up 'work done' waiters (flush) when
- * the last function has been fully processed.
- */
- if (atomic_dec_and_test(&cwq->nr_queued))
- wake_up(&cwq->work_done);
-
spin_lock_irqsave(&cwq->lock, flags);
+ cwq->remove_sequence++;
+ wake_up(&cwq->work_done);
}
spin_unlock_irqrestore(&cwq->lock, flags);
}
@@ -227,8 +225,13 @@ static int worker_thread(void *__startup
* Forces execution of the workqueue and blocks until its completion.
* This is typically used in driver shutdown handlers.
*
- * NOTE: if work is being added to the queue constantly by some other
- * context then this function might block indefinitely.
+ * This function will sample each workqueue's current insert_sequence number and
+ * will sleep until the head sequence is greater than or equal to that. This
+ * means that we sleep until all works which were queued on entry have been
+ * handled, but we are not livelocked by new incoming ones.
+ *
+ * This function used to run the workqueues itself. Now we just wait for the
+ * helper threads to do it.
*/
void flush_workqueue(struct workqueue_struct *wq)
{
@@ -236,40 +239,63 @@ void flush_workqueue(struct workqueue_st
int cpu;
for (cpu = 0; cpu < NR_CPUS; cpu++) {
+ DEFINE_WAIT(wait);
+ long sequence_needed;
+
if (!cpu_online(cpu))
continue;
cwq = wq->cpu_wq + cpu_logical_map(cpu);
- if (atomic_read(&cwq->nr_queued)) {
- DECLARE_WAITQUEUE(wait, current);
-
- if (!list_empty(&cwq->worklist))
- run_workqueue(cwq);
+ spin_lock_irq(&cwq->lock);
+ sequence_needed = cwq->insert_sequence;
- /*
- * Wait for helper thread(s) to finish up
- * the queue:
- */
- set_task_state(current, TASK_INTERRUPTIBLE);
- add_wait_queue(&cwq->work_done, &wait);
- if (atomic_read(&cwq->nr_queued))
- schedule();
- else
- set_task_state(current, TASK_RUNNING);
- remove_wait_queue(&cwq->work_done, &wait);
+ while (sequence_needed - cwq->remove_sequence > 0) {
+ prepare_to_wait(&cwq->work_done, &wait,
+ TASK_UNINTERRUPTIBLE);
+ spin_unlock_irq(&cwq->lock);
+ schedule();
+ spin_lock_irq(&cwq->lock);
}
+ finish_wait(&cwq->work_done, &wait);
+ spin_unlock_irq(&cwq->lock);
}
}
-struct workqueue_struct *create_workqueue(const char *name)
+static int create_workqueue_thread(struct workqueue_struct *wq,
+ const char *name,
+ int cpu)
{
- int ret, cpu, destroy = 0;
- struct cpu_workqueue_struct *cwq;
startup_t startup;
+ struct cpu_workqueue_struct *cwq = wq->cpu_wq + cpu_logical_map(cpu);
+ int ret;
+
+ spin_lock_init(&cwq->lock);
+ cwq->wq = wq;
+ cwq->thread = NULL;
+ cwq->insert_sequence = 0;
+ cwq->remove_sequence = 0;
+ INIT_LIST_HEAD(&cwq->worklist);
+ init_waitqueue_head(&cwq->more_work);
+ init_waitqueue_head(&cwq->work_done);
+ init_completion(&cwq->exit);
+
+ init_completion(&startup.done);
+ startup.cwq = cwq;
+ startup.name = name;
+ ret = kernel_thread(worker_thread, &startup, CLONE_FS | CLONE_FILES);
+ if (ret >= 0) {
+ wait_for_completion(&startup.done);
+ BUG_ON(!cwq->thread);
+ }
+ return ret;
+}
+
+struct workqueue_struct *create_workqueue(const char *name)
+{
+ int cpu, destroy = 0;
struct workqueue_struct *wq;
BUG_ON(strlen(name) > 10);
- startup.name = name;
wq = kmalloc(sizeof(*wq), GFP_KERNEL);
if (!wq)
@@ -278,26 +304,8 @@ struct workqueue_struct *create_workqueu
for (cpu = 0; cpu < NR_CPUS; cpu++) {
if (!cpu_online(cpu))
continue;
- cwq = wq->cpu_wq + cpu_logical_map(cpu);
-
- spin_lock_init(&cwq->lock);
- cwq->wq = wq;
- cwq->thread = NULL;
- atomic_set(&cwq->nr_queued, 0);
- INIT_LIST_HEAD(&cwq->worklist);
- init_waitqueue_head(&cwq->more_work);
- init_waitqueue_head(&cwq->work_done);
-
- init_completion(&startup.done);
- startup.cwq = cwq;
- ret = kernel_thread(worker_thread, &startup,
- CLONE_FS | CLONE_FILES);
- if (ret < 0)
+ if (create_workqueue_thread(wq, name, cpu) < 0)
destroy = 1;
- else {
- wait_for_completion(&startup.done);
- BUG_ON(!cwq->thread);
- }
}
/*
* Was there any error during startup? If yes then clean up:
@@ -309,27 +317,29 @@ struct workqueue_struct *create_workqueu
return wq;
}
-void destroy_workqueue(struct workqueue_struct *wq)
+static void cleanup_workqueue_thread(struct workqueue_struct *wq, int cpu)
{
struct cpu_workqueue_struct *cwq;
- int cpu;
- flush_workqueue(wq);
-
- for (cpu = 0; cpu < NR_CPUS; cpu++) {
- if (!cpu_online(cpu))
- continue;
- cwq = wq->cpu_wq + cpu_logical_map(cpu);
- if (!cwq->thread)
- continue;
- /*
- * Initiate an exit and wait for it:
- */
- init_completion(&cwq->exit);
+ cwq = wq->cpu_wq + cpu_logical_map(cpu);
+ if (cwq->thread) {
+ /* Tell thread to exit and wait for it. */
cwq->thread = NULL;
wake_up(&cwq->more_work);
wait_for_completion(&cwq->exit);
+ }
+}
+
+void destroy_workqueue(struct workqueue_struct *wq)
+{
+ int cpu;
+
+ flush_workqueue(wq);
+
+ for (cpu = 0; cpu < NR_CPUS; cpu++) {
+ if (cpu_online(cpu))
+ cleanup_workqueue_thread(wq, cpu);
}
kfree(wq);
}
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/