USB: usb-storage: use kthread_stop() for the control thread

This patch (as923) makes usb-storage's control thread use
kthread_should_stop()/kthread_stop().  The scanning thread can't be
similarly converted until the core kthread implementation allows
threads to call do_exit().

The advantage of this change is that we can now be certain the control
thread has terminated before storage_disconnect() returns.  This will
simplify the locking requirements when autosuspend support is added.

Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Matthew Dharm <mdharm-usb@one-eyed-alien.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

2 files changed, 14 insertions, 25 deletions

diff --git a/drivers/usb/storage/usb.c b/drivers/usb/storage/usb.c
index 00521f1d6a6b..cf3fc91234e7 100644
--- a/drivers/usb/storage/usb.c
+++ b/drivers/usb/storage/usb.c
@@ -425,23 +425,15 @@ SkipForAbort:
                 mutex_unlock(&us->dev_mutex);
         } /* for (;;) */
 
-        scsi_host_put(host);
-
-        /* notify the exit routine that we're actually exiting now 
-         *
-         * complete()/wait_for_completion() is similar to up()/down(),
-         * except that complete() is safe in the case where the structure
-         * is getting deleted in a parallel mode of execution (i.e. just
-         * after the down() -- that's necessary for the thread-shutdown
-         * case.
-         *
-         * complete_and_exit() goes even further than this -- it is safe in
-         * the case that the thread of the caller is going away (not just
-         * the structure) -- this is necessary for the module-remove case.
-         * This is important in preemption kernels, which transfer the flow
-         * of execution immediately upon a complete().
-         */
-        complete_and_exit(&threads_gone, 0);
+        /* Wait until we are told to stop */
+        for (;;) {
+                set_current_state(TASK_INTERRUPTIBLE);
+                if (kthread_should_stop())
+                        break;
+                schedule();
+        }
+        __set_current_state(TASK_RUNNING);
+        return 0;
 }       
 
 /***********************************************************************
@@ -809,19 +801,13 @@ static int usb_stor_acquire_resources(struct us_data *us)
         }
 
         /* Start up our control thread */
-        th = kthread_create(usb_stor_control_thread, us, "usb-storage");
+        th = kthread_run(usb_stor_control_thread, us, "usb-storage");
         if (IS_ERR(th)) {
                 printk(KERN_WARNING USB_STORAGE 
                        "Unable to start control thread\n");
                 return PTR_ERR(th);
         }
-
-        /* Take a reference to the host for the control thread and
-         * count it among all the threads we have launched.  Then
-         * start it up. */
-        scsi_host_get(us_to_host(us));
-        atomic_inc(&total_threads);
-        wake_up_process(th);
+        us->ctl_thread = th;
 
         return 0;
 }
@@ -838,6 +824,8 @@ static void usb_stor_release_resources(struct us_data *us)
         US_DEBUGP("-- sending exit command to thread\n");
         set_bit(US_FLIDX_DISCONNECTING, &us->flags);
         up(&us->sema);
+        if (us->ctl_thread)
+                kthread_stop(us->ctl_thread);
 
         /* Call the destructor routine, if it exists */
         if (us->extra_destructor) {
diff --git a/drivers/usb/storage/usb.h b/drivers/usb/storage/usb.h
index 6dac1ffdde86..6445665b1577 100644
--- a/drivers/usb/storage/usb.h
+++ b/drivers/usb/storage/usb.h
@@ -144,6 +144,7 @@ struct us_data {
         unsigned char           *sensebuf;       /* sense data buffer    */
         dma_addr_t              cr_dma;          /* buffer DMA addresses */
         dma_addr_t              iobuf_dma;
+        struct task_struct      *ctl_thread;     /* the control thread   */
 
         /* mutual exclusion and synchronization structures */
         struct semaphore        sema;            /* to sleep thread on      */