WorkStruct: Merge the pending bit into the wq_data pointer

Reclaim a word from the size of the work_struct by folding the pending bit and
the wq_data pointer together.  This shouldn't cause misalignment problems as
all pointers should be at least 4-byte aligned.

Signed-Off-By: David Howells <dhowells@redhat.com>

diff --git a/drivers/block/floppy.c b/drivers/block/floppy.c
index 5a14fac..aa1eb44 100644 (file)
--- a/drivers/block/floppy.c
+++ b/drivers/block/floppy.c
@@ -1868,7 +1868,7 @@ static void show_floppy(void)
        printk("fdc_busy=%lu\n", fdc_busy);
        if (do_floppy)
                printk("do_floppy=%p\n", do_floppy);
-       if (floppy_work.pending)
+       if (work_pending(&floppy_work))
                printk("floppy_work.func=%p\n", floppy_work.func);
        if (timer_pending(&fd_timer))
                printk("fd_timer.function=%p\n", fd_timer.function);
@@ -4498,7 +4498,7 @@ static void floppy_release_irq_and_dma(void)
                printk("floppy timer still active:%s\n", timeout_message);
        if (timer_pending(&fd_timer))
                printk("auxiliary floppy timer still active\n");
-       if (floppy_work.pending)
+       if (work_pending(&floppy_work))
                printk("work still pending\n");
 #endif
        old_fdc = fdc;

diff --git a/include/linux/workqueue.h b/include/linux/workqueue.h
index cef40b2..ecc017d 100644 (file)
--- a/include/linux/workqueue.h
+++ b/include/linux/workqueue.h
@@ -14,11 +14,15 @@ struct workqueue_struct;
 typedef void (*work_func_t)(void *data);
 
 struct work_struct {
-       unsigned long pending;
+       /* the first word is the work queue pointer and the pending flag
+        * rolled into one */
+       unsigned long management;
+#define WORK_STRUCT_PENDING 0          /* T if work item pending execution */
+#define WORK_STRUCT_FLAG_MASK (3UL)
+#define WORK_STRUCT_WQ_DATA_MASK (~WORK_STRUCT_FLAG_MASK)
        struct list_head entry;
        work_func_t func;
        void *data;
-       void *wq_data;
 };
 
 struct delayed_work {
@@ -65,7 +69,7 @@ struct execute_work {
 #define INIT_WORK(_work, _func, _data)                         \
        do {                                                    \
                INIT_LIST_HEAD(&(_work)->entry);                \
-               (_work)->pending = 0;                           \
+               (_work)->management = 0;                        \
                PREPARE_WORK((_work), (_func), (_data));        \
        } while (0)
 
@@ -75,6 +79,21 @@ struct execute_work {
                init_timer(&(_work)->timer);                    \
        } while (0)
 
+/**
+ * work_pending - Find out whether a work item is currently pending
+ * @work: The work item in question
+ */
+#define work_pending(work) \
+       test_bit(WORK_STRUCT_PENDING, &(work)->management)
+
+/**
+ * delayed_work_pending - Find out whether a delayable work item is currently
+ * pending
+ * @work: The work item in question
+ */
+#define delayed_work_pending(work) \
+       test_bit(WORK_STRUCT_PENDING, &(work)->work.management)
+
 
 extern struct workqueue_struct *__create_workqueue(const char *name,
                                                    int singlethread);
@@ -115,7 +134,7 @@ static inline int cancel_delayed_work(struct delayed_work *work)
 
        ret = del_timer_sync(&work->timer);
        if (ret)
-               clear_bit(0, &work->work.pending);
+               clear_bit(WORK_STRUCT_PENDING, &work->work.management);
        return ret;
 }
 

diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index 1e9d61e..9674797 100644 (file)
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -80,6 +80,29 @@ static inline int is_single_threaded(struct workqueue_struct *wq)
        return list_empty(&wq->list);
 }
 
+static inline void set_wq_data(struct work_struct *work, void *wq)
+{
+       unsigned long new, old, res;
+
+       /* assume the pending flag is already set and that the task has already
+        * been queued on this workqueue */
+       new = (unsigned long) wq | (1UL << WORK_STRUCT_PENDING);
+       res = work->management;
+       if (res != new) {
+               do {
+                       old = res;
+                       new = (unsigned long) wq;
+                       new |= (old & WORK_STRUCT_FLAG_MASK);
+                       res = cmpxchg(&work->management, old, new);
+               } while (res != old);
+       }
+}
+
+static inline void *get_wq_data(struct work_struct *work)
+{
+       return (void *) (work->management & WORK_STRUCT_WQ_DATA_MASK);
+}
+
 /* Preempt must be disabled. */
 static void __queue_work(struct cpu_workqueue_struct *cwq,
                         struct work_struct *work)
@@ -87,7 +110,7 @@ static void __queue_work(struct cpu_workqueue_struct *cwq,
        unsigned long flags;
 
        spin_lock_irqsave(&cwq->lock, flags);
-       work->wq_data = cwq;
+       set_wq_data(work, cwq);
        list_add_tail(&work->entry, &cwq->worklist);
        cwq->insert_sequence++;
        wake_up(&cwq->more_work);
@@ -108,7 +131,7 @@ int fastcall queue_work(struct workqueue_struct *wq, struct work_struct *work)
 {
        int ret = 0, cpu = get_cpu();
 
-       if (!test_and_set_bit(0, &work->pending)) {
+       if (!test_and_set_bit(WORK_STRUCT_PENDING, &work->management)) {
                if (unlikely(is_single_threaded(wq)))
                        cpu = singlethread_cpu;
                BUG_ON(!list_empty(&work->entry));
@@ -123,7 +146,7 @@ EXPORT_SYMBOL_GPL(queue_work);
 static void delayed_work_timer_fn(unsigned long __data)
 {
        struct delayed_work *dwork = (struct delayed_work *)__data;
-       struct workqueue_struct *wq = dwork->work.wq_data;
+       struct workqueue_struct *wq = get_wq_data(&dwork->work);
        int cpu = smp_processor_id();
 
        if (unlikely(is_single_threaded(wq)))
@@ -150,12 +173,12 @@ int fastcall queue_delayed_work(struct workqueue_struct *wq,
        if (delay == 0)
                return queue_work(wq, work);
 
-       if (!test_and_set_bit(0, &work->pending)) {
+       if (!test_and_set_bit(WORK_STRUCT_PENDING, &work->management)) {
                BUG_ON(timer_pending(timer));
                BUG_ON(!list_empty(&work->entry));
 
                /* This stores wq for the moment, for the timer_fn */
-               work->wq_data = wq;
+               set_wq_data(work, wq);
                timer->expires = jiffies + delay;
                timer->data = (unsigned long)dwork;
                timer->function = delayed_work_timer_fn;
@@ -182,12 +205,12 @@ int queue_delayed_work_on(int cpu, struct workqueue_struct *wq,
        struct timer_list *timer = &dwork->timer;
        struct work_struct *work = &dwork->work;
 
-       if (!test_and_set_bit(0, &work->pending)) {
+       if (!test_and_set_bit(WORK_STRUCT_PENDING, &work->management)) {
                BUG_ON(timer_pending(timer));
                BUG_ON(!list_empty(&work->entry));
 
                /* This stores wq for the moment, for the timer_fn */
-               work->wq_data = wq;
+               set_wq_data(work, wq);
                timer->expires = jiffies + delay;
                timer->data = (unsigned long)dwork;
                timer->function = delayed_work_timer_fn;
@@ -223,8 +246,8 @@ static void run_workqueue(struct cpu_workqueue_struct *cwq)
                list_del_init(cwq->worklist.next);
                spin_unlock_irqrestore(&cwq->lock, flags);
 
-               BUG_ON(work->wq_data != cwq);
-               clear_bit(0, &work->pending);
+               BUG_ON(get_wq_data(work) != cwq);
+               clear_bit(WORK_STRUCT_PENDING, &work->management);
                f(data);
 
                spin_lock_irqsave(&cwq->lock, flags);