USB: create new workqueue thread for USB autosuspend

This patch (as787) creates a new workqueue thread to handle delayed
USB autosuspend requests.  Previously the code used keventd.  However
it turns out that the hub driver's suspend routine calls
flush_scheduled_work(), making it a poor candidate for running in
keventd (the call immediately deadlocks).  The solution is to use a
new thread instead of keventd.

Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

3 files changed, 46 insertions, 8 deletions

diff --git a/drivers/usb/core/driver.c b/drivers/usb/core/driver.c
index c2aad6a4d49f..ee18d187ca17 100644
--- a/drivers/usb/core/driver.c
+++ b/drivers/usb/core/driver.c
@@ -24,6 +24,7 @@
 
 #include <linux/device.h>
 #include <linux/usb.h>
+#include <linux/workqueue.h>
 #include "hcd.h"
 #include "usb.h"
 
@@ -1131,7 +1132,7 @@ void usb_autosuspend_device(struct usb_device *udev, int dec_usage_cnt)
         mutex_lock_nested(&udev->pm_mutex, udev->level);
         udev->pm_usage_cnt -= dec_usage_cnt;
         if (udev->pm_usage_cnt <= 0)
-                schedule_delayed_work(&udev->autosuspend,
+                queue_delayed_work(ksuspend_usb_wq, &udev->autosuspend,
                                 USB_AUTOSUSPEND_DELAY);
         mutex_unlock(&udev->pm_mutex);
         // dev_dbg(&udev->dev, "%s: cnt %d\n",
@@ -1215,10 +1216,10 @@ void usb_autopm_put_interface(struct usb_interface *intf)
         struct usb_device       *udev = interface_to_usbdev(intf);
 
         mutex_lock_nested(&udev->pm_mutex, udev->level);
-        if (intf->condition != USB_INTERFACE_UNBOUND) {
-                if (--intf->pm_usage_cnt <= 0)
-                        schedule_delayed_work(&udev->autosuspend,
-                                        USB_AUTOSUSPEND_DELAY);
+        if (intf->condition != USB_INTERFACE_UNBOUND &&
+                        --intf->pm_usage_cnt <= 0) {
+                queue_delayed_work(ksuspend_usb_wq, &udev->autosuspend,
+                                USB_AUTOSUSPEND_DELAY);
         }
         mutex_unlock(&udev->pm_mutex);
         // dev_dbg(&intf->dev, "%s: cnt %d\n",
diff --git a/drivers/usb/core/usb.c b/drivers/usb/core/usb.c
index 60ef4ef0101a..239f8e5d247f 100644
--- a/drivers/usb/core/usb.c
+++ b/drivers/usb/core/usb.c
@@ -33,6 +33,7 @@
 #include <linux/smp_lock.h>
 #include <linux/usb.h>
 #include <linux/mutex.h>
+#include <linux/workqueue.h>
 
 #include <asm/io.h>
 #include <asm/scatterlist.h>
@@ -47,6 +48,8 @@ const char *usbcore_name = "usbcore";
 
 static int nousb;       /* Disable USB when built into kernel image */
 
+struct workqueue_struct *ksuspend_usb_wq;       /* For autosuspend */
+
 
 /**
  * usb_ifnum_to_if - get the interface object with a given interface number
@@ -170,9 +173,9 @@ static void usb_release_dev(struct device *dev)
 
         udev = to_usb_device(dev);
 
-#ifdef  CONFIG_PM
+#ifdef  CONFIG_USB_SUSPEND
         cancel_delayed_work(&udev->autosuspend);
-        flush_scheduled_work();
+        flush_workqueue(ksuspend_usb_wq);
 #endif
         usb_destroy_configuration(udev);
         usb_put_hcd(bus_to_hcd(udev->bus));
@@ -184,6 +187,28 @@ static void usb_release_dev(struct device *dev)
 
 #ifdef  CONFIG_PM
 
+static int ksuspend_usb_init(void)
+{
+        ksuspend_usb_wq = create_singlethread_workqueue("ksuspend_usbd");
+        if (!ksuspend_usb_wq)
+                return -ENOMEM;
+        return 0;
+}
+
+static void ksuspend_usb_cleanup(void)
+{
+        destroy_workqueue(ksuspend_usb_wq);
+}
+
+#else
+
+#define ksuspend_usb_init()     0
+#define ksuspend_usb_cleanup()  do {} while (0)
+
+#endif
+
+#ifdef  CONFIG_USB_SUSPEND
+
 /* usb_autosuspend_work - callback routine to autosuspend a USB device */
 static void usb_autosuspend_work(void *_udev)
 {
@@ -195,6 +220,11 @@ static void usb_autosuspend_work(void *_udev)
         mutex_unlock(&udev->pm_mutex);
 }
 
+#else
+
+static void usb_autosuspend_work(void *_udev)
+{}
+
 #endif
 
 /**
@@ -976,9 +1006,12 @@ static int __init usb_init(void)
                 return 0;
         }
 
+        retval = ksuspend_usb_init();
+        if (retval)
+                goto out;
         retval = bus_register(&usb_bus_type);
         if (retval) 
-                goto out;
+                goto bus_register_failed;
         retval = usb_host_init();
         if (retval)
                 goto host_init_failed;
@@ -1014,6 +1047,8 @@ major_init_failed:
         usb_host_cleanup();
 host_init_failed:
         bus_unregister(&usb_bus_type);
+bus_register_failed:
+        ksuspend_usb_cleanup();
 out:
         return retval;
 }
@@ -1035,6 +1070,7 @@ static void __exit usb_exit(void)
         usb_hub_cleanup();
         usb_host_cleanup();
         bus_unregister(&usb_bus_type);
+        ksuspend_usb_cleanup();
 }
 
 subsys_initcall(usb_init);
diff --git a/drivers/usb/core/usb.h b/drivers/usb/core/usb.h
index 0c09ecced6e1..fb6eb41c374f 100644
--- a/drivers/usb/core/usb.h
+++ b/drivers/usb/core/usb.h
@@ -62,6 +62,7 @@ extern int usb_autoresume_device(struct usb_device *udev, int inc_busy_cnt);
 
 #endif
 
+extern struct workqueue_struct *ksuspend_usb_wq;
 extern struct bus_type usb_bus_type;
 extern struct usb_device_driver usb_generic_driver;