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Subject[RFC] Input: input-polldev - create workqueue upfront
Input: input-polldev - create workqueue upfront

From: Dmitry Torokhov <dmitry.torokhov@gmail.com>

With introduction of concurrency-managed work queues there is no point
in creating workqueues on demand; they can be created upfront as it does
not cause creation of unused threads.

Signed-off-by: Dmitry Torokhov <dtor@mail.ru>
---

I wonder if it would be even simpler if we had a freezable system-wide
workqueue, in addition to system_wq, system_long_wq, system_nrt_wq and
system_unbound_wq...

drivers/input/input-polldev.c | 72 ++++++++++++++---------------------------
1 files changed, 24 insertions(+), 48 deletions(-)


diff --git a/drivers/input/input-polldev.c b/drivers/input/input-polldev.c
index 3037842..0a5304c 100644
--- a/drivers/input/input-polldev.c
+++ b/drivers/input/input-polldev.c
@@ -13,6 +13,7 @@
#include <linux/jiffies.h>
#include <linux/slab.h>
#include <linux/mutex.h>
+#include <linux/workqueue.h>
#include <linux/input-polldev.h>

MODULE_AUTHOR("Dmitry Torokhov <dtor@mail.ru>");
@@ -20,44 +21,8 @@ MODULE_DESCRIPTION("Generic implementation of a polled input device");
MODULE_LICENSE("GPL v2");
MODULE_VERSION("0.1");

-static DEFINE_MUTEX(polldev_mutex);
-static int polldev_users;
static struct workqueue_struct *polldev_wq;

-static int input_polldev_start_workqueue(void)
-{
- int retval;
-
- retval = mutex_lock_interruptible(&polldev_mutex);
- if (retval)
- return retval;
-
- if (!polldev_users) {
- polldev_wq = create_singlethread_workqueue("ipolldevd");
- if (!polldev_wq) {
- pr_err("failed to create ipolldevd workqueue\n");
- retval = -ENOMEM;
- goto out;
- }
- }
-
- polldev_users++;
-
- out:
- mutex_unlock(&polldev_mutex);
- return retval;
-}
-
-static void input_polldev_stop_workqueue(void)
-{
- mutex_lock(&polldev_mutex);
-
- if (!--polldev_users)
- destroy_workqueue(polldev_wq);
-
- mutex_unlock(&polldev_mutex);
-}
-
static void input_polldev_queue_work(struct input_polled_dev *dev)
{
unsigned long delay;
@@ -81,11 +46,6 @@ static void input_polled_device_work(struct work_struct *work)
static int input_open_polled_device(struct input_dev *input)
{
struct input_polled_dev *dev = input_get_drvdata(input);
- int error;
-
- error = input_polldev_start_workqueue();
- if (error)
- return error;

if (dev->open)
dev->open(dev);
@@ -102,13 +62,6 @@ static void input_close_polled_device(struct input_dev *input)
struct input_polled_dev *dev = input_get_drvdata(input);

cancel_delayed_work_sync(&dev->work);
- /*
- * Clean up work struct to remove references to the workqueue.
- * It may be destroyed by the next call. This causes problems
- * at next device open-close in case of poll_interval == 0.
- */
- INIT_DELAYED_WORK(&dev->work, dev->work.work.func);
- input_polldev_stop_workqueue();

if (dev->close)
dev->close(dev);
@@ -296,3 +249,26 @@ void input_unregister_polled_device(struct input_polled_dev *dev)
}
EXPORT_SYMBOL(input_unregister_polled_device);

+static int __init input_polldev_init(void)
+{
+ /*
+ * We are using a dedicated workqueue because we want it to
+ * be freezable. This ensures that we stop polling when
+ * system goes into sleep mode.
+ */
+ polldev_wq = alloc_workqueue("ipolldev_wq",
+ WQ_FREEZEABLE | WQ_UNBOUND, 0);
+ if (!polldev_wq) {
+ pr_err("failed to create ipolldev_wq workqueue\n");
+ return -ENOMEM;
+ }
+
+ return 0;
+}
+module_init(input_polldev_init);
+
+static void __exit input_polldev_exit(void)
+{
+ destroy_workqueue(polldev_wq);
+}
+module_exit(input_polldev_exit);

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