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>

diff --git a/drivers/usb/core/driver.c b/drivers/usb/core/driver.c
index c2aad6a..ee18d18 100644 (file)
--- 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 60ef4ef..239f8e5 100644 (file)
--- 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 0c09ecc..fb6eb41 100644 (file)
--- 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;