From: Eric W. Biederman <ebiederm@xmission.com>

This patch modifies the startup of kadbprobe to use kthread_run instead of
scheduling a work event which later calls kernel_thread and in the thread
calls daemonize and blocks signals.  kthread_run is simpler and more
maintainable.

The variable pid_t adb_probe_task_pid is replaced by a struct task_struct
variable named adb_probe_task.  Which works equally well with for testing
if the current process is the adb_probe thread, does not get confused in
the presence of a pid namespace and is easier to compare against current as
it is the same type.

The result is code that is slightly simpler and easier to maintain.

Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mackerras <paulus@samba.org>
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 drivers/macintosh/adb.c |   32 +++++++-------------------------
 1 files changed, 7 insertions(+), 25 deletions(-)

diff -puN drivers/macintosh/adb.c~macintosh-adb-convert-to-the-kthread-api drivers/macintosh/adb.c
--- a/drivers/macintosh/adb.c~macintosh-adb-convert-to-the-kthread-api
+++ a/drivers/macintosh/adb.c
@@ -35,6 +35,7 @@
 #include <linux/spinlock.h>
 #include <linux/completion.h>
 #include <linux/device.h>
+#include <linux/kthread.h>
 
 #include <asm/uaccess.h>
 #include <asm/semaphore.h>
@@ -82,7 +83,7 @@ struct adb_driver *adb_controller;
 BLOCKING_NOTIFIER_HEAD(adb_client_list);
 static int adb_got_sleep;
 static int adb_inited;
-static pid_t adb_probe_task_pid;
+static struct task_struct *adb_probe_task;
 static DECLARE_MUTEX(adb_probe_mutex);
 static struct completion adb_probe_task_comp;
 static int sleepy_trackpad;
@@ -137,8 +138,7 @@ static void printADBreply(struct adb_req
 
 static __inline__ void adb_wait_ms(unsigned int ms)
 {
-	if (current->pid && adb_probe_task_pid &&
-	  adb_probe_task_pid == current->pid)
+	if (adb_probe_task == current)
 		msleep(ms);
 	else
 		mdelay(ms);
@@ -245,35 +245,19 @@ static int adb_scan_bus(void)
  * This kernel task handles ADB probing. It dies once probing is
  * completed.
  */
-static int
-adb_probe_task(void *x)
+static int adb_probe(void *x)
 {
-	sigset_t blocked;
-
-	strcpy(current->comm, "kadbprobe");
-
-	sigfillset(&blocked);
-	sigprocmask(SIG_BLOCK, &blocked, NULL);
-	flush_signals(current);
 
 	printk(KERN_INFO "adb: starting probe task...\n");
 	do_adb_reset_bus();
 	printk(KERN_INFO "adb: finished probe task...\n");
 	
-	adb_probe_task_pid = 0;
+	adb_probe_task = NULL;
 	up(&adb_probe_mutex);
 	
 	return 0;
 }
 
-static void
-__adb_probe_task(struct work_struct *bullshit)
-{
-	adb_probe_task_pid = kernel_thread(adb_probe_task, NULL, SIGCHLD | CLONE_KERNEL);
-}
-
-static DECLARE_WORK(adb_reset_work, __adb_probe_task);
-
 int
 adb_reset_bus(void)
 {
@@ -283,7 +267,7 @@ adb_reset_bus(void)
 	}
 
 	down(&adb_probe_mutex);
-	schedule_work(&adb_reset_work);
+	adb_probe_task = kthread_run(adb_probe, NULL, "kadbprobe");
 	return 0;
 }
 
@@ -469,9 +453,7 @@ adb_request(struct adb_request *req, voi
 	/* Synchronous requests send from the probe thread cause it to
 	 * block. Beware that the "done" callback will be overriden !
 	 */
-	if ((flags & ADBREQ_SYNC) &&
-	    (current->pid && adb_probe_task_pid &&
-	    adb_probe_task_pid == current->pid)) {
+	if ((flags & ADBREQ_SYNC) && (current == adb_probe_task)) {
 		req->done = adb_probe_wakeup;
 		rc = adb_controller->send_request(req, 0);
 		if (rc || req->complete)
_