I think we can get rid of the spinlock protecting the kthread from being
interrupted by a wakeup in certain parts.
Even with the current implementation of the kthread the only lost wakeup
scenario could happen if the wakeup occurs between the kfifo_len check
and setting the state to TASK_INTERRUPTIBLE.
In the changed version we could lose a wakeup if it occurs between
processing the fifo content and setting the state to TASK_INTERRUPTIBLE.
This scenario is covered by an additional check for available events in
the fifo and setting the state to TASK_RUNNING in this case.
In addition the changed version flushes the kfifo before ending
when the kthread is stopped.
With this patch we gain:
- Get rid of the spinlock
- Simplify code
- Don't grep / release the mutex for each individual event but just once
for the complete fifo content. This reduces overhead if a driver e.g.
triggers processing after writing the content of a hw fifo to the kfifo.
Signed-off-by: Heiner Kallweit <hkallweit1@xxxxxxxxx>
---
drivers/media/rc/rc-core-priv.h | 2 --
drivers/media/rc/rc-ir-raw.c | 46 +++++++++++++++--------------------------
2 files changed, 17 insertions(+), 31 deletions(-)
diff --git a/drivers/media/rc/rc-core-priv.h b/drivers/media/rc/rc-core-priv.h
index 585d5e5..577128a 100644
--- a/drivers/media/rc/rc-core-priv.h
+++ b/drivers/media/rc/rc-core-priv.h
@@ -20,7 +20,6 @@
#define MAX_IR_EVENT_SIZE 512
#include <linux/slab.h>
-#include <linux/spinlock.h>
#include <media/rc-core.h>
struct ir_raw_handler {
@@ -37,7 +36,6 @@ struct ir_raw_handler {
struct ir_raw_event_ctrl {
struct list_head list; /* to keep track of raw clients */
struct task_struct *thread;
- spinlock_t lock;
/* fifo for the pulse/space durations */
DECLARE_KFIFO(kfifo, struct ir_raw_event, MAX_IR_EVENT_SIZE);
ktime_t last_event; /* when last event occurred */
diff --git a/drivers/media/rc/rc-ir-raw.c b/drivers/media/rc/rc-ir-raw.c
index 205ecc6..71a3e17 100644
--- a/drivers/media/rc/rc-ir-raw.c
+++ b/drivers/media/rc/rc-ir-raw.c
@@ -17,7 +17,6 @@
#include <linux/mutex.h>
#include <linux/kmod.h>
#include <linux/sched.h>
-#include <linux/freezer.h>
#include "rc-core-priv.h"
/* Used to keep track of IR raw clients, protected by ir_raw_handler_lock */
@@ -35,32 +34,26 @@ static int ir_raw_event_thread(void *data)
struct ir_raw_handler *handler;
struct ir_raw_event_ctrl *raw = (struct ir_raw_event_ctrl *)data;
- while (!kthread_should_stop()) {
-
- spin_lock_irq(&raw->lock);
-
- if (!kfifo_len(&raw->kfifo)) {
- set_current_state(TASK_INTERRUPTIBLE);
-
- if (kthread_should_stop())
- set_current_state(TASK_RUNNING);
-
- spin_unlock_irq(&raw->lock);
- schedule();
- continue;
+ while (1) {
+ mutex_lock(&ir_raw_handler_lock);
+ while (kfifo_out(&raw->kfifo, &ev, 1)) {
+ list_for_each_entry(handler, &ir_raw_handler_list, list)
+ if (raw->dev->enabled_protocols &
+ handler->protocols || !handler->protocols)
+ handler->decode(raw->dev, ev);
+ raw->prev_ev = ev;
}
+ mutex_unlock(&ir_raw_handler_lock);
- if(!kfifo_out(&raw->kfifo, &ev, 1))
- dev_err(&raw->dev->dev, "IR event FIFO is empty!\n");
- spin_unlock_irq(&raw->lock);
+ set_current_state(TASK_INTERRUPTIBLE);
- mutex_lock(&ir_raw_handler_lock);
- list_for_each_entry(handler, &ir_raw_handler_list, list)
- if (raw->dev->enabled_protocols & handler->protocols ||
- !handler->protocols)
- handler->decode(raw->dev, ev);
- raw->prev_ev = ev;
- mutex_unlock(&ir_raw_handler_lock);
+ if (kthread_should_stop()) {
+ __set_current_state(TASK_RUNNING);
+ break;
+ } else if (!kfifo_is_empty(&raw->kfifo))
+ set_current_state(TASK_RUNNING);
+
+ schedule();
}
return 0;
@@ -219,14 +212,10 @@ EXPORT_SYMBOL_GPL(ir_raw_event_set_idle);
*/
void ir_raw_event_handle(struct rc_dev *dev)
{
- unsigned long flags;
-
if (!dev->raw)
return;
- spin_lock_irqsave(&dev->raw->lock, flags);
wake_up_process(dev->raw->thread);
- spin_unlock_irqrestore(&dev->raw->lock, flags);
}
EXPORT_SYMBOL_GPL(ir_raw_event_handle);
@@ -274,7 +263,6 @@ int ir_raw_event_register(struct rc_dev *dev)
dev->change_protocol = change_protocol;
INIT_KFIFO(dev->raw->kfifo);
- spin_lock_init(&dev->raw->lock);
dev->raw->thread = kthread_run(ir_raw_event_thread, dev->raw,
"rc%u", dev->minor);
--
2.9.0
--
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