V4L/DVB: IR: replace workqueue with kthread

It is perfectly possible to have ir_raw_event_work
running concurently on two cpus, thus we must protect
it from that situation.

This stems from the fact that if hardware sends short packets of samples
we might end up queueing the work item more times that nessesary.

Such job isn't well suited for a workqueue, so use a kernel thread.

Signed-off-by: Maxim Levitsky <maximlevitsky@gmail.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

diff --git a/drivers/media/IR/ir-core-priv.h b/drivers/media/IR/ir-core-priv.h
index dc26e2beeefb06a05c62a538d6a0ade2d5d86e7d..84c7a9a5cad4526f4fbc6f1ce30637df0544669e 100644 (file)
--- a/drivers/media/IR/ir-core-priv.h
+++ b/drivers/media/IR/ir-core-priv.h
@@ -32,7 +32,7 @@ struct ir_raw_handler {
 
 struct ir_raw_event_ctrl {
        struct list_head                list;           /* to keep track of raw clients */
-       struct work_struct              rx_work;        /* for the rx decoding workqueue */
+       struct task_struct              *thread;
        struct kfifo                    kfifo;          /* fifo for the pulse/space durations */
        ktime_t                         last_event;     /* when last event occurred */
        enum raw_event_type             last_type;      /* last event type */

diff --git a/drivers/media/IR/ir-raw-event.c b/drivers/media/IR/ir-raw-event.c
index 9d5c029cfc0c09503425778dbfe53e67517cb45c..d0c18db4c0d3774f7d72c21b25d192714d9d7472 100644 (file)
--- a/drivers/media/IR/ir-raw-event.c
+++ b/drivers/media/IR/ir-raw-event.c
@@ -12,9 +12,10 @@
  *  GNU General Public License for more details.
  */
 
-#include <linux/workqueue.h>
+#include <linux/kthread.h>
 #include <linux/mutex.h>
 #include <linux/sched.h>
+#include <linux/freezer.h>
 #include "ir-core-priv.h"
 
 /* Define the max number of pulse/space transitions to buffer */
@@ -33,20 +34,30 @@ static u64 available_protocols;
 static struct work_struct wq_load;
 #endif
 
-static void ir_raw_event_work(struct work_struct *work)
+static int ir_raw_event_thread(void *data)
 {
        struct ir_raw_event ev;
        struct ir_raw_handler *handler;
-       struct ir_raw_event_ctrl *raw =
-               container_of(work, struct ir_raw_event_ctrl, rx_work);
+       struct ir_raw_event_ctrl *raw = (struct ir_raw_event_ctrl *)data;
+
+       while (!kthread_should_stop()) {
+               try_to_freeze();
 
-       while (kfifo_out(&raw->kfifo, &ev, sizeof(ev)) == sizeof(ev)) {
                mutex_lock(&ir_raw_handler_lock);
-               list_for_each_entry(handler, &ir_raw_handler_list, list)
-                       handler->decode(raw->input_dev, ev);
+
+               while (kfifo_out(&raw->kfifo, &ev, sizeof(ev)) == sizeof(ev)) {
+                       list_for_each_entry(handler, &ir_raw_handler_list, list)
+                               handler->decode(raw->input_dev, ev);
+                       raw->prev_ev = ev;
+               }
+
                mutex_unlock(&ir_raw_handler_lock);
-               raw->prev_ev = ev;
+
+               set_current_state(TASK_INTERRUPTIBLE);
+               schedule();
        }
+
+       return 0;
 }
 
 /**
@@ -141,7 +152,7 @@ void ir_raw_event_handle(struct input_dev *input_dev)
        if (!ir->raw)
                return;
 
-       schedule_work(&ir->raw->rx_work);
+       wake_up_process(ir->raw->thread);
 }
 EXPORT_SYMBOL_GPL(ir_raw_event_handle);
 
@@ -170,7 +181,7 @@ int ir_raw_event_register(struct input_dev *input_dev)
                return -ENOMEM;
 
        ir->raw->input_dev = input_dev;
-       INIT_WORK(&ir->raw->rx_work, ir_raw_event_work);
+
        ir->raw->enabled_protocols = ~0;
        rc = kfifo_alloc(&ir->raw->kfifo, sizeof(s64) * MAX_IR_EVENT_SIZE,
                         GFP_KERNEL);
@@ -180,6 +191,15 @@ int ir_raw_event_register(struct input_dev *input_dev)
                return rc;
        }
 
+       ir->raw->thread = kthread_run(ir_raw_event_thread, ir->raw,
+                       "rc%u",  (unsigned int)ir->devno);
+
+       if (IS_ERR(ir->raw->thread)) {
+               kfree(ir->raw);
+               ir->raw = NULL;
+               return PTR_ERR(ir->raw->thread);
+       }
+
        mutex_lock(&ir_raw_handler_lock);
        list_add_tail(&ir->raw->list, &ir_raw_client_list);
        list_for_each_entry(handler, &ir_raw_handler_list, list)
@@ -198,7 +218,7 @@ void ir_raw_event_unregister(struct input_dev *input_dev)
        if (!ir->raw)
                return;
 
-       cancel_work_sync(&ir->raw->rx_work);
+       kthread_stop(ir->raw->thread);
 
        mutex_lock(&ir_raw_handler_lock);
        list_del(&ir->raw->list);