[Devel] Re: [PATCH] bluetooth rfcomm: Convert to kthread API.

[Cedric Le Goater]

Andrew Morton wrote:
> On Thu, 19 Apr 2007 01:58:54 -0600
> "Eric W. Biederman" <ebiederm at xmission.com> wrote:
> 
>> From: Eric W. Biederman <ebiederm at xmission.com>
>>
>> This patch starts krfcommd using kthread_run instead of a combination
>> of kernel_thread and daemonize making the code slightly simpler
>> and more maintainable.
> 
> gargh, the more I look at these things, the more I agree with Christoph.
> 
>> Cc: Marcel Holtmann <marcel at holtmann.org>
>> Signed-off-by: Eric W. Biederman <ebiederm at xmission.com>
>> ---
>>  net/bluetooth/rfcomm/core.c |    4 ++--
>>  1 files changed, 2 insertions(+), 2 deletions(-)
>>
>> diff --git a/net/bluetooth/rfcomm/core.c b/net/bluetooth/rfcomm/core.c
>> index 34f993a..baaad49 100644
>> --- a/net/bluetooth/rfcomm/core.c
>> +++ b/net/bluetooth/rfcomm/core.c
>> @@ -38,6 +38,7 @@
>>  #include <linux/net.h>
>>  #include <linux/mutex.h>
>>  #include <linux/freezer.h>
>> +#include <linux/kthread.h>
>>  
>>  #include <net/sock.h>
>>  #include <asm/uaccess.h>
>> @@ -1938,7 +1939,6 @@ static int rfcomm_run(void *unused)
>>  
>>  	atomic_inc(&running);
>>  
>> -	daemonize("krfcommd");
>>  	set_user_nice(current, -10);
>>  
>>  	BT_DBG("");
>> @@ -2058,7 +2058,7 @@ static int __init rfcomm_init(void)
>>  
>>  	hci_register_cb(&rfcomm_cb);
>>  
>> -	kernel_thread(rfcomm_run, NULL, CLONE_KERNEL);
>> +	kthread_run(rfcomm_run, NULL, "krfcommd");
>>  
>>  	if (class_create_file(bt_class, &class_attr_rfcomm_dlc) < 0)
>>  		BT_ERR("Failed to create RFCOMM info file");
> 
> We should remove the file-wide `terminate' and `running' and switch the
> thread management over to kthread_run(), kthread_stop() and
> kthread_should_stop().


here's an old refreshed one using kthread_stop() and fixing the racy 
wakeup.

C.

Signed-off-by: Cedric Le Goater <clg at fr.ibm.com>

---
 net/bluetooth/rfcomm/core.c |   61 +++++++++++++++-----------------------------
 1 file changed, 21 insertions(+), 40 deletions(-)

Index: 2.6.21-rc6-mm1/net/bluetooth/rfcomm/core.c
===================================================================
--- 2.6.21-rc6-mm1.orig/net/bluetooth/rfcomm/core.c
+++ 2.6.21-rc6-mm1/net/bluetooth/rfcomm/core.c
@@ -38,6 +38,7 @@
 #include <linux/net.h>
 #include <linux/mutex.h>
 #include <linux/freezer.h>
+#include <linux/kthread.h>
 
 #include <net/sock.h>
 #include <asm/uaccess.h>
@@ -68,7 +69,6 @@ static DEFINE_MUTEX(rfcomm_mutex);
 static unsigned long rfcomm_event;
 
 static LIST_HEAD(session_list);
-static atomic_t terminate, running;
 
 static int rfcomm_send_frame(struct rfcomm_session *s, u8 *data, int len);
 static int rfcomm_send_sabm(struct rfcomm_session *s, u8 dlci);
@@ -1847,28 +1847,6 @@ static inline void rfcomm_process_sessio
 	rfcomm_unlock();
 }
 
-static void rfcomm_worker(void)
-{
-	BT_DBG("");
-
-	while (!atomic_read(&terminate)) {
-		try_to_freeze();
-
-		if (!test_bit(RFCOMM_SCHED_WAKEUP, &rfcomm_event)) {
-			/* No pending events. Let's sleep.
-			 * Incoming connections and data will wake us up. */
-			set_current_state(TASK_INTERRUPTIBLE);
-			schedule();
-		}
-
-		/* Process stuff */
-		clear_bit(RFCOMM_SCHED_WAKEUP, &rfcomm_event);
-		rfcomm_process_sessions();
-	}
-	set_current_state(TASK_RUNNING);
-	return;
-}
-
 static int rfcomm_add_listener(bdaddr_t *ba)
 {
 	struct sockaddr_l2 addr;
@@ -1934,22 +1912,29 @@ static void rfcomm_kill_listener(void)
 
 static int rfcomm_run(void *unused)
 {
-	rfcomm_thread = current;
-
-	atomic_inc(&running);
-
-	daemonize("krfcommd");
 	set_user_nice(current, -10);
 
 	BT_DBG("");
 
 	rfcomm_add_listener(BDADDR_ANY);
 
-	rfcomm_worker();
+	while (!kthread_should_stop()) {
+		try_to_freeze();
 
-	rfcomm_kill_listener();
+		set_current_state(TASK_INTERRUPTIBLE);
+		if (!test_bit(RFCOMM_SCHED_WAKEUP, &rfcomm_event)) {
+			/* No pending events. Let's sleep.
+			 * Incoming connections and data will wake us up. */
+			schedule();
+		}
 
-	atomic_dec(&running);
+		/* Process stuff */
+		clear_bit(RFCOMM_SCHED_WAKEUP, &rfcomm_event);
+		rfcomm_process_sessions();
+	}
+	set_current_state(TASK_RUNNING);
+
+	rfcomm_kill_listener();
 	return 0;
 }
 
@@ -2058,7 +2043,9 @@ static int __init rfcomm_init(void)
 
 	hci_register_cb(&rfcomm_cb);
 
-	kernel_thread(rfcomm_run, NULL, CLONE_KERNEL);
+	rfcomm_thread = kthread_run(rfcomm_run, NULL, "krfcommd");
+	if (IS_ERR(rfcomm_thread))
+		return PTR_ERR(rfcomm_thread);
 
 	if (class_create_file(bt_class, &class_attr_rfcomm_dlc) < 0)
 		BT_ERR("Failed to create RFCOMM info file");
@@ -2080,14 +2067,8 @@ static void __exit rfcomm_exit(void)
 
 	hci_unregister_cb(&rfcomm_cb);
 
-	/* Terminate working thread.
-	 * ie. Set terminate flag and wake it up */
-	atomic_inc(&terminate);
-	rfcomm_schedule(RFCOMM_SCHED_STATE);
-
-	/* Wait until thread is running */
-	while (atomic_read(&running))
-		schedule();
+	/* Terminate working thread */
+	kthread_stop(rfcomm_thread);
 
 #ifdef CONFIG_BT_RFCOMM_TTY
 	rfcomm_cleanup_ttys();