Re: [PATCH] ibmphp: Convert to use the kthreads API

[Christoph Hellwig <hch@infradead.org>]

On Thu, Apr 19, 2007 at 12:55:30AM -0600, Eric W. Biederman wrote:
> From: Eric W. Biederman <ebiederm@xmission.com> - unquoted
> 
> kthread_run replaces kernel_thread and dameonize.
> 
> allow_signal is unnecessary and has been removed.
> tid_poll was unused and has been removed.

Thread handling in this driver is quite interesting. Greg has his name
in there, so we can blame everything on him ;-)

Below is my take at cleaning at least the thread-related bits up:

 - full switch to kthread infrastructure
 - switch semOperations to a mutex, and give it a proper name
 - remove the useless hpc_poll_thread wrapper
 - remove ibmphp_hpc_initvars - everything left can easily be
   initialized statically


Signed-off-by: Christoph Hellwig <hch@lst.de>

Index: linux-2.6/drivers/pci/hotplug/ibmphp.h
===================================================================
--- linux-2.6.orig/drivers/pci/hotplug/ibmphp.h	2007-04-22 12:44:04.000000000 +0200
+++ linux-2.6/drivers/pci/hotplug/ibmphp.h	2007-04-22 12:44:07.000000000 +0200
@@ -392,7 +392,6 @@ extern int ibmphp_add_pfmem_from_mem (st
 extern struct bus_node *ibmphp_find_res_bus (u8);
 extern void ibmphp_print_test (void);	/* for debugging purposes */
 
-extern void ibmphp_hpc_initvars (void);
 extern int ibmphp_hpc_readslot (struct slot *, u8, u8 *);
 extern int ibmphp_hpc_writeslot (struct slot *, u8);
 extern void ibmphp_lock_operations (void);
Index: linux-2.6/drivers/pci/hotplug/ibmphp_core.c
===================================================================
--- linux-2.6.orig/drivers/pci/hotplug/ibmphp_core.c	2007-04-22 12:44:11.000000000 +0200
+++ linux-2.6/drivers/pci/hotplug/ibmphp_core.c	2007-04-22 12:44:16.000000000 +0200
@@ -1368,8 +1368,6 @@ static int __init ibmphp_init(void)
 
 	ibmphp_debug = debug;
 
-	ibmphp_hpc_initvars();
-
 	for (i = 0; i < 16; i++)
 		irqs[i] = 0;
 
Index: linux-2.6/drivers/pci/hotplug/ibmphp_hpc.c
===================================================================
--- linux-2.6.orig/drivers/pci/hotplug/ibmphp_hpc.c	2007-04-22 12:31:23.000000000 +0200
+++ linux-2.6/drivers/pci/hotplug/ibmphp_hpc.c	2007-04-22 12:45:51.000000000 +0200
@@ -35,6 +35,7 @@
 #include <linux/smp_lock.h>
 #include <linux/init.h>
 #include <linux/mutex.h>
+#include <linux/kthread.h>
 
 #include "ibmphp.h"
 
@@ -101,12 +102,10 @@ static int to_debug = 0;
 //----------------------------------------------------------------------------
 // global variables
 //----------------------------------------------------------------------------
-static int ibmphp_shutdown;
-static int tid_poll;
-static struct mutex sem_hpcaccess;	// lock access to HPC
-static struct semaphore semOperations;	// lock all operations and
+static struct task_struct *ibmphp_poll_thread;
+static DEFINE_MUTEX(sem_hpcaccess);	// lock access to HPC
+static DEFINE_MUTEX(ibmphp_op_sem);	// lock all operations and
 					// access to data structures
-static struct semaphore sem_exit;	// make sure polling thread goes away
 //----------------------------------------------------------------------------
 // local function prototypes
 //----------------------------------------------------------------------------
@@ -116,33 +115,11 @@ static u8 hpc_writecmdtoindex (u8, u8);
 static u8 hpc_readcmdtoindex (u8, u8);
 static void get_hpc_access (void);
 static void free_hpc_access (void);
-static void poll_hpc (void);
 static int process_changeinstatus (struct slot *, struct slot *);
 static int process_changeinlatch (u8, u8, struct controller *);
-static int hpc_poll_thread (void *);
 static int hpc_wait_ctlr_notworking (int, struct controller *, void __iomem *, u8 *);
 //----------------------------------------------------------------------------
 
-
-/*----------------------------------------------------------------------
-* Name:    ibmphp_hpc_initvars
-*
-* Action:  initialize semaphores and variables
-*---------------------------------------------------------------------*/
-void __init ibmphp_hpc_initvars (void)
-{
-	debug ("%s - Entry\n", __FUNCTION__);
-
-	mutex_init(&sem_hpcaccess);
-	init_MUTEX (&semOperations);
-	init_MUTEX_LOCKED (&sem_exit);
-	to_debug = 0;
-	ibmphp_shutdown = 0;
-	tid_poll = 0;
-
-	debug ("%s - Exit\n", __FUNCTION__);
-}
-
 /*----------------------------------------------------------------------
 * Name:    i2c_ctrl_read
 *
@@ -798,7 +775,7 @@ void free_hpc_access (void)
 *---------------------------------------------------------------------*/
 void ibmphp_lock_operations (void)
 {
-	down (&semOperations);
+	mutex_lock(&ibmphp_op_sem);
 	to_debug = 1;
 }
 
@@ -808,7 +785,7 @@ void ibmphp_lock_operations (void)
 void ibmphp_unlock_operations (void)
 {
 	debug ("%s - Entry\n", __FUNCTION__);
-	up (&semOperations);
+	mutex_unlock(&ibmphp_op_sem);
 	to_debug = 0;
 	debug ("%s - Exit\n", __FUNCTION__);
 }
@@ -819,7 +796,7 @@ void ibmphp_unlock_operations (void)
 #define POLL_LATCH_REGISTER	0
 #define POLL_SLOTS		1
 #define POLL_SLEEP		2
-static void poll_hpc (void)
+static int poll_hpc(void *data)
 {
 	struct slot myslot;
 	struct slot *pslot = NULL;
@@ -833,12 +810,9 @@ static void poll_hpc (void)
 
 	debug ("%s - Entry\n", __FUNCTION__);
 
-	while (!ibmphp_shutdown) {
-		if (ibmphp_shutdown) 
-			break;
-		
+	while (!kthread_should_stop()) {
 		/* try to get the lock to do some kind of hardware access */
-		down (&semOperations);
+		mutex_lock(&ibmphp_op_sem);
 
 		switch (poll_state) {
 		case POLL_LATCH_REGISTER: 
@@ -893,14 +867,13 @@ static void poll_hpc (void)
 			break;
 		case POLL_SLEEP:
 			/* don't sleep with a lock on the hardware */
-			up (&semOperations);
+			mutex_unlock(&ibmphp_op_sem);
 			msleep(POLL_INTERVAL_SEC * 1000);
 
-			if (ibmphp_shutdown) 
+			if (kthread_should_stop())
 				break;
 			
-			down (&semOperations);
-			
+			mutex_lock(&ibmphp_op_sem);
 			if (poll_count >= POLL_LATCH_CNT) {
 				poll_count = 0;
 				poll_state = POLL_SLOTS;
@@ -909,12 +882,13 @@ static void poll_hpc (void)
 			break;
 		}	
 		/* give up the hardware semaphore */
-		up (&semOperations);
+		mutex_unlock(&ibmphp_op_sem);
 		/* sleep for a short time just for good measure */
 		msleep(100);
 	}
-	up (&sem_exit);
 	debug ("%s - Exit\n", __FUNCTION__);
+
+	return 0;
 }
 
 
@@ -1050,47 +1024,19 @@ static int process_changeinlatch (u8 old
 }
 
 /*----------------------------------------------------------------------
-* Name:    hpc_poll_thread
-*
-* Action:  polling
-*
-* Return   0
-* Value:
-*---------------------------------------------------------------------*/
-static int hpc_poll_thread (void *data)
-{
-	debug ("%s - Entry\n", __FUNCTION__);
-
-	daemonize("hpc_poll");
-	allow_signal(SIGKILL);
-
-	poll_hpc ();
-
-	tid_poll = 0;
-	debug ("%s - Exit\n", __FUNCTION__);
-	return 0;
-}
-
-
-/*----------------------------------------------------------------------
 * Name:    ibmphp_hpc_start_poll_thread
 *
 * Action:  start polling thread
 *---------------------------------------------------------------------*/
 int __init ibmphp_hpc_start_poll_thread (void)
 {
-	int rc = 0;
-
-	debug ("%s - Entry\n", __FUNCTION__);
-
-	tid_poll = kernel_thread (hpc_poll_thread, NULL, 0);
-	if (tid_poll < 0) {
+	ibmphp_poll_thread = kthread_run(poll_hpc, NULL, "hpc_poll");
+	if (IS_ERR(ibmphp_poll_thread)) {
 		err ("%s - Error, thread not started\n", __FUNCTION__);
-		rc = -1;
+		return PTR_ERR(ibmphp_poll_thread);
 	}
 
-	debug ("%s - Exit tid_poll[%d] rc[%d]\n", __FUNCTION__, tid_poll, rc);
-	return rc;
+	return 0;
 }
 
 /*----------------------------------------------------------------------
@@ -1100,28 +1046,11 @@ int __init ibmphp_hpc_start_poll_thread 
 *---------------------------------------------------------------------*/
 void __exit ibmphp_hpc_stop_poll_thread (void)
 {
-	debug ("%s - Entry\n", __FUNCTION__);
+	kthread_stop(ibmphp_poll_thread);
 
-	ibmphp_shutdown = 1;
-	debug ("before locking operations \n");
 	ibmphp_lock_operations ();
-	debug ("after locking operations \n");
-	
-	// wait for poll thread to exit
-	debug ("before sem_exit down \n");
-	down (&sem_exit);
-	debug ("after sem_exit down \n");
-
-	// cleanup
-	debug ("before free_hpc_access \n");
 	free_hpc_access ();
-	debug ("after free_hpc_access \n");
 	ibmphp_unlock_operations ();
-	debug ("after unlock operations \n");
-	up (&sem_exit);
-	debug ("after sem exit up\n");
-
-	debug ("%s - Exit\n", __FUNCTION__);
 }
 
 /*----------------------------------------------------------------------