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-rw-r--r--Documentation/slow-work.txt12
-rw-r--r--include/linux/slow-work.h2
-rw-r--r--kernel/slow-work.c81
3 files changed, 88 insertions, 7 deletions
diff --git a/Documentation/slow-work.txt b/Documentation/slow-work.txt
index c655c51..2e384bd 100644
--- a/Documentation/slow-work.txt
+++ b/Documentation/slow-work.txt
@@ -108,7 +108,17 @@ on the item, 0 otherwise.
The items are reference counted, so there ought to be no need for a flush
-operation. When all a module's slow work items have been processed, and the
+operation. But as the reference counting is optional, means to cancel
+existing work items are also included:
+
+ cancel_slow_work(&myitem);
+
+can be used to cancel pending work. The above cancel function waits for
+existing work to have been executed (or prevent execution of them, depending
+on timing).
+
+
+When all a module's slow work items have been processed, and the
module has no further interest in the facility, it should unregister its
interest:
diff --git a/include/linux/slow-work.h b/include/linux/slow-work.h
index 9adb2b3..eef2018 100644
--- a/include/linux/slow-work.h
+++ b/include/linux/slow-work.h
@@ -51,6 +51,7 @@ struct slow_work {
#define SLOW_WORK_EXECUTING 1 /* item currently executing */
#define SLOW_WORK_ENQ_DEFERRED 2 /* item enqueue deferred */
#define SLOW_WORK_VERY_SLOW 3 /* item is very slow */
+#define SLOW_WORK_CANCELLING 4 /* item is being cancelled, don't enqueue */
const struct slow_work_ops *ops; /* operations table for this item */
struct list_head link; /* link in queue */
};
@@ -88,6 +89,7 @@ static inline void vslow_work_init(struct slow_work *work,
}
extern int slow_work_enqueue(struct slow_work *work);
+extern void slow_work_cancel(struct slow_work *work);
extern int slow_work_register_user(struct module *owner);
extern void slow_work_unregister_user(struct module *owner);
diff --git a/kernel/slow-work.c b/kernel/slow-work.c
index fccf421..671cc43 100644
--- a/kernel/slow-work.c
+++ b/kernel/slow-work.c
@@ -236,12 +236,17 @@ static bool slow_work_execute(int id)
if (!test_and_clear_bit(SLOW_WORK_PENDING, &work->flags))
BUG();
- work->ops->execute(work);
+ /* don't execute if the work is in the process of being cancelled */
+ if (!test_bit(SLOW_WORK_CANCELLING, &work->flags))
+ work->ops->execute(work);
if (very_slow)
atomic_dec(&vslow_work_executing_count);
clear_bit_unlock(SLOW_WORK_EXECUTING, &work->flags);
+ /* wake up anyone waiting for this work to be complete */
+ wake_up_bit(&work->flags, SLOW_WORK_EXECUTING);
+
/* if someone tried to enqueue the item whilst we were executing it,
* then it'll be left unenqueued to avoid multiple threads trying to
* execute it simultaneously
@@ -314,11 +319,16 @@ auto_requeue:
* allowed to pick items to execute. This ensures that very slow items won't
* overly block ones that are just ordinarily slow.
*
- * Returns 0 if successful, -EAGAIN if not.
+ * Returns 0 if successful, -EAGAIN if not (or -ECANCELED if cancelled work is
+ * attempted queued)
*/
int slow_work_enqueue(struct slow_work *work)
{
unsigned long flags;
+ int ret;
+
+ if (test_bit(SLOW_WORK_CANCELLING, &work->flags))
+ return -ECANCELED;
BUG_ON(slow_work_user_count <= 0);
BUG_ON(!work);
@@ -335,6 +345,9 @@ int slow_work_enqueue(struct slow_work *work)
if (!test_and_set_bit_lock(SLOW_WORK_PENDING, &work->flags)) {
spin_lock_irqsave(&slow_work_queue_lock, flags);
+ if (unlikely(test_bit(SLOW_WORK_CANCELLING, &work->flags)))
+ goto cancelled;
+
/* we promise that we will not attempt to execute the work
* function in more than one thread simultaneously
*
@@ -352,8 +365,9 @@ int slow_work_enqueue(struct slow_work *work)
if (test_bit(SLOW_WORK_EXECUTING, &work->flags)) {
set_bit(SLOW_WORK_ENQ_DEFERRED, &work->flags);
} else {
- if (slow_work_get_ref(work) < 0)
- goto cant_get_ref;
+ ret = slow_work_get_ref(work);
+ if (ret < 0)
+ goto failed;
if (test_bit(SLOW_WORK_VERY_SLOW, &work->flags))
list_add_tail(&work->link, &vslow_work_queue);
else
@@ -365,12 +379,67 @@ int slow_work_enqueue(struct slow_work *work)
}
return 0;
-cant_get_ref:
+cancelled:
+ ret = -ECANCELED;
+failed:
spin_unlock_irqrestore(&slow_work_queue_lock, flags);
- return -EAGAIN;
+ return ret;
}
EXPORT_SYMBOL(slow_work_enqueue);
+static int slow_work_wait(void *word)
+{
+ schedule();
+ return 0;
+}
+
+/**
+ * slow_work_cancel - Cancel a slow work item
+ * @work: The work item to cancel
+ *
+ * This function will cancel a previously enqueued work item. If we cannot
+ * cancel the work item, it is guarenteed to have run when this function
+ * returns.
+ */
+void slow_work_cancel(struct slow_work *work)
+{
+ bool wait = true, put = false;
+
+ set_bit(SLOW_WORK_CANCELLING, &work->flags);
+
+ spin_lock_irq(&slow_work_queue_lock);
+
+ if (test_bit(SLOW_WORK_PENDING, &work->flags) &&
+ !list_empty(&work->link)) {
+ /* the link in the pending queue holds a reference on the item
+ * that we will need to release */
+ list_del_init(&work->link);
+ wait = false;
+ put = true;
+ clear_bit(SLOW_WORK_PENDING, &work->flags);
+
+ } else if (test_and_clear_bit(SLOW_WORK_ENQ_DEFERRED, &work->flags)) {
+ /* the executor is holding our only reference on the item, so
+ * we merely need to wait for it to finish executing */
+ clear_bit(SLOW_WORK_PENDING, &work->flags);
+ }
+
+ spin_unlock_irq(&slow_work_queue_lock);
+
+ /* the EXECUTING flag is set by the executor whilst the spinlock is set
+ * and before the item is dequeued - so assuming the above doesn't
+ * actually dequeue it, simply waiting for the EXECUTING flag to be
+ * released here should be sufficient */
+ if (wait)
+ wait_on_bit(&work->flags, SLOW_WORK_EXECUTING, slow_work_wait,
+ TASK_UNINTERRUPTIBLE);
+
+ clear_bit(SLOW_WORK_CANCELLING, &work->flags);
+ if (put)
+ slow_work_put_ref(work);
+}
+EXPORT_SYMBOL(slow_work_cancel);
+
/*
* Schedule a cull of the thread pool at some time in the near future
*/