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[media] rc: refactor raw handler kthread
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@gmail.com> Signed-off-by: Sean Young <sean@mess.org> Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>
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parent
0cffd6312f
commit
74d47d75be
2 changed files with 18 additions and 32 deletions
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@ -20,7 +20,6 @@
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#define MAX_IR_EVENT_SIZE 512
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#include <linux/slab.h>
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#include <linux/spinlock.h>
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#include <media/rc-core.h>
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struct ir_raw_handler {
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@ -37,7 +36,6 @@ struct ir_raw_handler {
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struct ir_raw_event_ctrl {
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struct list_head list; /* to keep track of raw clients */
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struct task_struct *thread;
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spinlock_t lock;
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/* fifo for the pulse/space durations */
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DECLARE_KFIFO(kfifo, struct ir_raw_event, MAX_IR_EVENT_SIZE);
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ktime_t last_event; /* when last event occurred */
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@ -17,7 +17,6 @@
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#include <linux/mutex.h>
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#include <linux/kmod.h>
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#include <linux/sched.h>
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#include <linux/freezer.h>
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#include "rc-core-priv.h"
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/* Used to keep track of IR raw clients, protected by ir_raw_handler_lock */
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@ -34,32 +33,26 @@ static int ir_raw_event_thread(void *data)
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struct ir_raw_handler *handler;
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struct ir_raw_event_ctrl *raw = (struct ir_raw_event_ctrl *)data;
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while (!kthread_should_stop()) {
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spin_lock_irq(&raw->lock);
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if (!kfifo_len(&raw->kfifo)) {
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set_current_state(TASK_INTERRUPTIBLE);
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if (kthread_should_stop())
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set_current_state(TASK_RUNNING);
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spin_unlock_irq(&raw->lock);
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schedule();
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continue;
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}
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if(!kfifo_out(&raw->kfifo, &ev, 1))
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dev_err(&raw->dev->dev, "IR event FIFO is empty!\n");
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spin_unlock_irq(&raw->lock);
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while (1) {
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mutex_lock(&ir_raw_handler_lock);
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list_for_each_entry(handler, &ir_raw_handler_list, list)
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if (raw->dev->enabled_protocols & handler->protocols ||
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!handler->protocols)
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handler->decode(raw->dev, ev);
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raw->prev_ev = ev;
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while (kfifo_out(&raw->kfifo, &ev, 1)) {
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list_for_each_entry(handler, &ir_raw_handler_list, list)
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if (raw->dev->enabled_protocols &
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handler->protocols || !handler->protocols)
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handler->decode(raw->dev, ev);
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raw->prev_ev = ev;
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}
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mutex_unlock(&ir_raw_handler_lock);
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set_current_state(TASK_INTERRUPTIBLE);
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if (kthread_should_stop()) {
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__set_current_state(TASK_RUNNING);
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break;
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} else if (!kfifo_is_empty(&raw->kfifo))
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set_current_state(TASK_RUNNING);
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schedule();
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}
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return 0;
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@ -218,14 +211,10 @@ EXPORT_SYMBOL_GPL(ir_raw_event_set_idle);
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*/
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void ir_raw_event_handle(struct rc_dev *dev)
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{
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unsigned long flags;
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if (!dev->raw)
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return;
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spin_lock_irqsave(&dev->raw->lock, flags);
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wake_up_process(dev->raw->thread);
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spin_unlock_irqrestore(&dev->raw->lock, flags);
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}
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EXPORT_SYMBOL_GPL(ir_raw_event_handle);
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@ -269,7 +258,6 @@ int ir_raw_event_register(struct rc_dev *dev)
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dev->change_protocol = change_protocol;
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INIT_KFIFO(dev->raw->kfifo);
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spin_lock_init(&dev->raw->lock);
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dev->raw->thread = kthread_run(ir_raw_event_thread, dev->raw,
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"rc%u", dev->minor);
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