Re: [PATCH] saa7134-tvaudio: Convert to kthread API.

[Cedric Le Goater]

Eric W. Biederman wrote:
> From: Eric W. Biederman <ebiederm@xxxxxxxxxxxx> - unquoted
> 
> It is my goal to replace all kernel code that handles signals
> from user space, calls kernel_thread or calls daemonize.  All
> of which the kthread_api makes unncessary.  Handling signals
> from user space is a maintenance problem becuase using a
> kernel thread is an implementation detail and if user space
> cares it does not allow us to change the implementation.  Calling
> daemonize is a problem because it has to undo a continually changing
> set of state generated by user space, requiring the implemetation
> to change continually.  kernel_thread is a problem because it
> returns a pid_t value.  Numeric pids are inherently racy and
> in the presence of a pid namespace they are no longer global
> making them useless for general use in the kernel.
> 
> So this patch renames the pid member of struct saa7134_thread
> started and changes it's type from pid_t to int.  All it
> has ever been used for is to detect if the kernel thread
> is has been started so this works.
> 
> allow_signal(SIGTERM) and the calls to signal_pending have
> been removed they are needed for the driver to operation.
> 
> The startup of tvaudio_thread and tvaudio_thread_dep have
> been modified to use kthread_run instead of a combination
> of kernel_thread and daemonize.
> 
> The result is code that is slightly simpler and more
> maintainable.

Here's a refreshed attempt using kthread_should_stop(). 
Unfortunately, not tested bc we don't have the hardware. 

cheers,

C.

From: Sukadev Bhattiprolu <sukadev@xxxxxxxxxx>

Replace kernel_thread() with kthread_run() since kernel_thread()
is deprecated in drivers/modules. Also remove signalling code
as it is not needed in the driver.

Signed-off-by: Sukadev Bhattiprolu <sukadev@xxxxxxxxxx>
Signed-off-by: Cedric Le Goater <clg@xxxxxxxxxx>
Cc: Mauro Carvalho Chehab <mchehab@xxxxxxxxxxxxx>
Cc: Containers@xxxxxxxxxxxxxx
Cc: video4linux-list@xxxxxxxxxx
Cc: v4l-dvb-maintainer@xxxxxxxxxxx

---
 drivers/media/video/saa7134/saa7134-tvaudio.c |   45 +++++++++++++-------------
 drivers/media/video/saa7134/saa7134.h         |    4 --
 2 files changed, 24 insertions(+), 25 deletions(-)

Index: 2.6.21-rc6-mm1/drivers/media/video/saa7134/saa7134.h
===================================================================
--- 2.6.21-rc6-mm1.orig/drivers/media/video/saa7134/saa7134.h
+++ 2.6.21-rc6-mm1/drivers/media/video/saa7134/saa7134.h
@@ -324,10 +324,8 @@ struct saa7134_pgtable {
 
 /* tvaudio thread status */
 struct saa7134_thread {
-	pid_t                      pid;
-	struct completion          exit;
+	struct task_struct *       task;
 	wait_queue_head_t          wq;
-	unsigned int               shutdown;
 	unsigned int               scan1;
 	unsigned int               scan2;
 	unsigned int               mode;
Index: 2.6.21-rc6-mm1/drivers/media/video/saa7134/saa7134-tvaudio.c
===================================================================
--- 2.6.21-rc6-mm1.orig/drivers/media/video/saa7134/saa7134-tvaudio.c
+++ 2.6.21-rc6-mm1/drivers/media/video/saa7134/saa7134-tvaudio.c
@@ -27,6 +27,7 @@
 #include <linux/kernel.h>
 #include <linux/slab.h>
 #include <linux/delay.h>
+#include <linux/kthread.h>
 #include <asm/div64.h>
 
 #include "saa7134-reg.h"
@@ -344,16 +345,22 @@ static int tvaudio_sleep(struct saa7134_
 	DECLARE_WAITQUEUE(wait, current);
 
 	add_wait_queue(&dev->thread.wq, &wait);
-	if (dev->thread.scan1 == dev->thread.scan2 && !dev->thread.shutdown) {
+
+	set_current_state(TASK_INTERRUPTIBLE);
+
+	if (dev->thread.scan1 == dev->thread.scan2 && !kthread_should_stop()) {
 		if (timeout < 0) {
-			set_current_state(TASK_INTERRUPTIBLE);
 			schedule();
 		} else {
 			schedule_timeout_interruptible
 						(msecs_to_jiffies(timeout));
 		}
 	}
+
+	set_current_state(TASK_RUNNING);
+
 	remove_wait_queue(&dev->thread.wq, &wait);
+
 	return dev->thread.scan1 != dev->thread.scan2;
 }
 
@@ -505,11 +512,9 @@ static int tvaudio_thread(void *data)
 	unsigned int i, audio, nscan;
 	int max1,max2,carrier,rx,mode,lastmode,default_carrier;
 
-	daemonize("%s", dev->name);
-	allow_signal(SIGTERM);
 	for (;;) {
 		tvaudio_sleep(dev,-1);
-		if (dev->thread.shutdown || signal_pending(current))
+		if (kthread_should_stop())
 			goto done;
 
 	restart:
@@ -618,7 +623,7 @@ static int tvaudio_thread(void *data)
 		for (;;) {
 			if (tvaudio_sleep(dev,5000))
 				goto restart;
-			if (dev->thread.shutdown || signal_pending(current))
+			if (kthread_should_stop())
 				break;
 			if (UNSET == dev->thread.mode) {
 				rx = tvaudio_getstereo(dev,&tvaudio[i]);
@@ -634,7 +639,6 @@ static int tvaudio_thread(void *data)
 	}
 
  done:
-	complete_and_exit(&dev->thread.exit, 0);
 	return 0;
 }
 
@@ -782,9 +786,6 @@ static int tvaudio_thread_ddep(void *dat
 	struct saa7134_dev *dev = data;
 	u32 value, norms, clock;
 
-	daemonize("%s", dev->name);
-	allow_signal(SIGTERM);
-
 	clock = saa7134_boards[dev->board].audio_clock;
 	if (UNSET != audio_clock_override)
 		clock = audio_clock_override;
@@ -796,7 +797,7 @@ static int tvaudio_thread_ddep(void *dat
 
 	for (;;) {
 		tvaudio_sleep(dev,-1);
-		if (dev->thread.shutdown || signal_pending(current))
+		if (kthread_should_stop())
 			goto done;
 
 	restart:
@@ -876,7 +877,6 @@ static int tvaudio_thread_ddep(void *dat
 	}
 
  done:
-	complete_and_exit(&dev->thread.exit, 0);
 	return 0;
 }
 
@@ -986,15 +986,16 @@ int saa7134_tvaudio_init2(struct saa7134
 		break;
 	}
 
-	dev->thread.pid = -1;
+	dev->thread.task = NULL;
 	if (my_thread) {
 		/* start tvaudio thread */
 		init_waitqueue_head(&dev->thread.wq);
-		init_completion(&dev->thread.exit);
-		dev->thread.pid = kernel_thread(my_thread,dev,0);
-		if (dev->thread.pid < 0)
-			printk(KERN_WARNING "%s: kernel_thread() failed\n",
+		dev->thread.task = kthread_run(my_thread, dev, dev->name);
+		if (IS_ERR(dev->thread.task)) {
+			printk(KERN_WARNING "%s: failed to create kthread\n",
 			       dev->name);
+			dev->thread.task = NULL;
+		}
 		saa7134_tvaudio_do_scan(dev);
 	}
 
@@ -1005,10 +1006,10 @@ int saa7134_tvaudio_init2(struct saa7134
 int saa7134_tvaudio_fini(struct saa7134_dev *dev)
 {
 	/* shutdown tvaudio thread */
-	if (dev->thread.pid >= 0) {
-		dev->thread.shutdown = 1;
-		wake_up_interruptible(&dev->thread.wq);
-		wait_for_completion(&dev->thread.exit);
+	if (dev->thread.task) {
+		/* kthread_stop() wakes up the thread */
+		kthread_stop(dev->thread.task);
+		dev->thread.task = NULL;
 	}
 	saa_andorb(SAA7134_ANALOG_IO_SELECT, 0x07, 0x00); /* LINE1 */
 	return 0;
@@ -1020,7 +1021,7 @@ int saa7134_tvaudio_do_scan(struct saa71
 		dprintk("sound IF not in use, skipping scan\n");
 		dev->automute = 0;
 		saa7134_tvaudio_setmute(dev);
-	} else if (dev->thread.pid >= 0) {
+	} else if (dev->thread.task) {
 		dev->thread.mode = UNSET;
 		dev->thread.scan2++;
 		wake_up_interruptible(&dev->thread.wq);
-
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