Gitweb:     
http://git.kernel.org/git/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=2f67cd5b1d5066d11761aebb0bf4b76bc253cc99
Commit:     2f67cd5b1d5066d11761aebb0bf4b76bc253cc99
Parent:     fa0de2b614ca89d14d046e6756ba020fd386ff71
Author:     Alan Stern <[EMAIL PROTECTED]>
AuthorDate: Thu Aug 16 16:16:00 2007 -0400
Committer:  Greg Kroah-Hartman <[EMAIL PROTECTED]>
CommitDate: Wed Aug 22 14:27:52 2007 -0700

    usb-storage: fix bugs in the disconnect pathway
    
    This patch (as961) fixes a couple of bugs in the disconnect pathway of
    usb-storage.
    
    The first problem, which apparently has been around for a while
    although nobody noticed it, shows up when an aborted command is still
    pending when a disconnect occurs.  The SCSI error-handler will
    continue to wait in command_abort() until the us->notify completion is
    signalled.  Thus quiesce_and_remove_host() needs to signal it.
    
    The second problem was introduced recently along with autosuspend
    support.  Since usb_stor_scan_thread() now calls
    usb_autopm_put_interface() before exiting, we can't simply leave the
    scanning thread running after a disconnect; we must wait until the
    thread exits.  This is solved by adding a new struct completion to the
    private data structure.  Fortuitously, it allows the removal of the
    rather clunky mechanism used in the past to insure that all threads
    have finished before the module is unloaded.
    
    Signed-off-by: Alan Stern <[EMAIL PROTECTED]>
    CC: Matthew Dharm <[EMAIL PROTECTED]>
    Signed-off-by: Greg Kroah-Hartman <[EMAIL PROTECTED]>
---
 drivers/usb/storage/usb.c |   33 ++++++---------------------------
 drivers/usb/storage/usb.h |    1 +
 2 files changed, 7 insertions(+), 27 deletions(-)

diff --git a/drivers/usb/storage/usb.c b/drivers/usb/storage/usb.c
index 28842d2..25e557d 100644
--- a/drivers/usb/storage/usb.c
+++ b/drivers/usb/storage/usb.c
@@ -112,13 +112,6 @@ module_param(delay_use, uint, S_IRUGO | S_IWUSR);
 MODULE_PARM_DESC(delay_use, "seconds to delay before using a new device");
 
 
-/* These are used to make sure the module doesn't unload before all the
- * threads have exited.
- */
-static atomic_t total_threads = ATOMIC_INIT(0);
-static DECLARE_COMPLETION(threads_gone);
-
-
 /*
  * The entries in this table correspond, line for line,
  * with the entries of us_unusual_dev_list[].
@@ -879,9 +872,6 @@ static void quiesce_and_remove_host(struct us_data *us)
        usb_stor_stop_transport(us);
        wake_up(&us->delay_wait);
 
-       /* It doesn't matter if the SCSI-scanning thread is still running.
-        * The thread will exit when it sees the DISCONNECTING flag. */
-
        /* queuecommand won't accept any new commands and the control
         * thread won't execute a previously-queued command.  If there
         * is such a command pending, complete it with an error. */
@@ -891,12 +881,16 @@ static void quiesce_and_remove_host(struct us_data *us)
                scsi_lock(host);
                us->srb->scsi_done(us->srb);
                us->srb = NULL;
+               complete(&us->notify);          /* in case of an abort */
                scsi_unlock(host);
        }
        mutex_unlock(&us->dev_mutex);
 
        /* Now we own no commands so it's safe to remove the SCSI host */
        scsi_remove_host(host);
+
+       /* Wait for the SCSI-scanning thread to stop */
+       wait_for_completion(&us->scanning_done);
 }
 
 /* Second stage of disconnect processing: deallocate all resources */
@@ -947,9 +941,8 @@ retry:
                /* Should we unbind if no devices were detected? */
        }
 
-       scsi_host_put(us_to_host(us));
        usb_autopm_put_interface(us->pusb_intf);
-       complete_and_exit(&threads_gone, 0);
+       complete_and_exit(&us->scanning_done, 0);
 }
 
 
@@ -984,6 +977,7 @@ static int storage_probe(struct usb_interface *intf,
        init_MUTEX_LOCKED(&(us->sema));
        init_completion(&(us->notify));
        init_waitqueue_head(&us->delay_wait);
+       init_completion(&us->scanning_done);
 
        /* Associate the us_data structure with the USB device */
        result = associate_dev(us, intf);
@@ -1033,11 +1027,6 @@ static int storage_probe(struct usb_interface *intf,
                goto BadDevice;
        }
 
-       /* Take a reference to the host for the scanning 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);
        usb_autopm_get_interface(intf); /* dropped in the scanning thread */
        wake_up_process(th);
 
@@ -1104,16 +1093,6 @@ static void __exit usb_stor_exit(void)
        US_DEBUGP("-- calling usb_deregister()\n");
        usb_deregister(&usb_storage_driver) ;
 
-       /* Don't return until all of our control and scanning threads
-        * have exited.  Since each thread signals threads_gone as its
-        * last act, we have to call wait_for_completion the right number
-        * of times.
-        */
-       while (atomic_read(&total_threads) > 0) {
-               wait_for_completion(&threads_gone);
-               atomic_dec(&total_threads);
-       }
-
        usb_usual_clear_present(USB_US_TYPE_STOR);
 }
 
diff --git a/drivers/usb/storage/usb.h b/drivers/usb/storage/usb.h
index 6445665..8d87503 100644
--- a/drivers/usb/storage/usb.h
+++ b/drivers/usb/storage/usb.h
@@ -150,6 +150,7 @@ struct us_data {
        struct semaphore        sema;            /* to sleep thread on      */
        struct completion       notify;          /* thread begin/end        */
        wait_queue_head_t       delay_wait;      /* wait during scan, reset */
+       struct completion       scanning_done;   /* wait for scan thread    */
 
        /* subdriver information */
        void                    *extra;          /* Any extra data          */
-
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