USB: make intf.pm_usage an atomic_t

This patch (as1260) changes the pm_usage_cnt field in struct
usb_interface from an int to an atomic_t.  This is so that drivers can
invoke the usb_autopm_get_interface_async() and
usb_autopm_put_interface_async() routines without locking and without
fear of corrupting the pm_usage_cnt value.

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

3 files changed, 28 insertions, 21 deletions

diff --git a/drivers/usb/core/driver.c b/drivers/usb/core/driver.c
index 1bad4e5a6abb..1c976c141f33 100644
--- a/drivers/usb/core/driver.c
+++ b/drivers/usb/core/driver.c
@@ -235,7 +235,7 @@ static int usb_probe_interface(struct device *dev)
                 /* The interface should always appear to be in use
                  * unless the driver suports autosuspend.
                  */
-                intf->pm_usage_cnt = !(driver->supports_autosuspend);
+                atomic_set(&intf->pm_usage_cnt, !driver->supports_autosuspend);
 
                 /* Carry out a deferred switch to altsetting 0 */
                 if (intf->needs_altsetting0) {
@@ -347,7 +347,7 @@ int usb_driver_claim_interface(struct usb_driver *driver,
         usb_pm_lock(udev);
         iface->condition = USB_INTERFACE_BOUND;
         mark_active(iface);
-        iface->pm_usage_cnt = !(driver->supports_autosuspend);
+        atomic_set(&iface->pm_usage_cnt, !driver->supports_autosuspend);
         usb_pm_unlock(udev);
 
         /* if interface was already added, bind now; else let
@@ -1068,7 +1068,7 @@ static int autosuspend_check(struct usb_device *udev, int reschedule)
                         intf = udev->actconfig->interface[i];
                         if (!is_active(intf))
                                 continue;
-                        if (intf->pm_usage_cnt > 0)
+                        if (atomic_read(&intf->pm_usage_cnt) > 0)
                                 return -EBUSY;
                         if (intf->needs_remote_wakeup &&
                                         !udev->do_remote_wakeup) {
@@ -1464,17 +1464,19 @@ static int usb_autopm_do_interface(struct usb_interface *intf,
                 status = -ENODEV;
         else {
                 udev->auto_pm = 1;
-                intf->pm_usage_cnt += inc_usage_cnt;
+                atomic_add(inc_usage_cnt, &intf->pm_usage_cnt);
                 udev->last_busy = jiffies;
-                if (inc_usage_cnt >= 0 && intf->pm_usage_cnt > 0) {
+                if (inc_usage_cnt >= 0 &&
+                                atomic_read(&intf->pm_usage_cnt) > 0) {
                         if (udev->state == USB_STATE_SUSPENDED)
                                 status = usb_resume_both(udev,
                                                 PMSG_AUTO_RESUME);
                         if (status != 0)
-                                intf->pm_usage_cnt -= inc_usage_cnt;
+                                atomic_sub(inc_usage_cnt, &intf->pm_usage_cnt);
                         else
                                 udev->last_busy = jiffies;
-                } else if (inc_usage_cnt <= 0 && intf->pm_usage_cnt <= 0) {
+                } else if (inc_usage_cnt <= 0 &&
+                                atomic_read(&intf->pm_usage_cnt) <= 0) {
                         status = usb_suspend_both(udev, PMSG_AUTO_SUSPEND);
                 }
         }
@@ -1519,7 +1521,7 @@ void usb_autopm_put_interface(struct usb_interface *intf)
 
         status = usb_autopm_do_interface(intf, -1);
         dev_vdbg(&intf->dev, "%s: status %d cnt %d\n",
-                        __func__, status, intf->pm_usage_cnt);
+                        __func__, status, atomic_read(&intf->pm_usage_cnt));
 }
 EXPORT_SYMBOL_GPL(usb_autopm_put_interface);
 
@@ -1547,10 +1549,10 @@ void usb_autopm_put_interface_async(struct usb_interface *intf)
                 status = -ENODEV;
         } else {
                 udev->last_busy = jiffies;
-                --intf->pm_usage_cnt;
+                atomic_dec(&intf->pm_usage_cnt);
                 if (udev->autosuspend_disabled || udev->autosuspend_delay < 0)
                         status = -EPERM;
-                else if (intf->pm_usage_cnt <= 0 &&
+                else if (atomic_read(&intf->pm_usage_cnt) <= 0 &&
                                 !timer_pending(&udev->autosuspend.timer)) {
                         queue_delayed_work(ksuspend_usb_wq, &udev->autosuspend,
                                         round_jiffies_up_relative(
@@ -1558,7 +1560,7 @@ void usb_autopm_put_interface_async(struct usb_interface *intf)
                 }
         }
         dev_vdbg(&intf->dev, "%s: status %d cnt %d\n",
-                        __func__, status, intf->pm_usage_cnt);
+                        __func__, status, atomic_read(&intf->pm_usage_cnt));
 }
 EXPORT_SYMBOL_GPL(usb_autopm_put_interface_async);
 
@@ -1602,7 +1604,7 @@ int usb_autopm_get_interface(struct usb_interface *intf)
 
         status = usb_autopm_do_interface(intf, 1);
         dev_vdbg(&intf->dev, "%s: status %d cnt %d\n",
-                        __func__, status, intf->pm_usage_cnt);
+                        __func__, status, atomic_read(&intf->pm_usage_cnt));
         return status;
 }
 EXPORT_SYMBOL_GPL(usb_autopm_get_interface);
@@ -1630,10 +1632,14 @@ int usb_autopm_get_interface_async(struct usb_interface *intf)
                 status = -ENODEV;
         else if (udev->autoresume_disabled)
                 status = -EPERM;
-        else if (++intf->pm_usage_cnt > 0 && udev->state == USB_STATE_SUSPENDED)
-                queue_work(ksuspend_usb_wq, &udev->autoresume);
+        else {
+                atomic_inc(&intf->pm_usage_cnt);
+                if (atomic_read(&intf->pm_usage_cnt) > 0 &&
+                                udev->state == USB_STATE_SUSPENDED)
+                        queue_work(ksuspend_usb_wq, &udev->autoresume);
+        }
         dev_vdbg(&intf->dev, "%s: status %d cnt %d\n",
-                        __func__, status, intf->pm_usage_cnt);
+                        __func__, status, atomic_read(&intf->pm_usage_cnt));
         return status;
 }
 EXPORT_SYMBOL_GPL(usb_autopm_get_interface_async);
@@ -1655,7 +1661,7 @@ int usb_autopm_set_interface(struct usb_interface *intf)
 
         status = usb_autopm_do_interface(intf, 0);
         dev_vdbg(&intf->dev, "%s: status %d cnt %d\n",
-                        __func__, status, intf->pm_usage_cnt);
+                        __func__, status, atomic_read(&intf->pm_usage_cnt));
         return status;
 }
 EXPORT_SYMBOL_GPL(usb_autopm_set_interface);
diff --git a/drivers/usb/core/hub.c b/drivers/usb/core/hub.c
index cb54420ed583..69e3a966a4b7 100644
--- a/drivers/usb/core/hub.c
+++ b/drivers/usb/core/hub.c
@@ -373,7 +373,7 @@ static void kick_khubd(struct usb_hub *hub)
         unsigned long   flags;
 
         /* Suppress autosuspend until khubd runs */
-        to_usb_interface(hub->intfdev)->pm_usage_cnt = 1;
+        atomic_set(&to_usb_interface(hub->intfdev)->pm_usage_cnt, 1);
 
         spin_lock_irqsave(&hub_event_lock, flags);
         if (!hub->disconnected && list_empty(&hub->event_list)) {
@@ -678,7 +678,8 @@ static void hub_activate(struct usb_hub *hub, enum hub_activation_type type)
                                         msecs_to_jiffies(delay));
 
                         /* Suppress autosuspend until init is done */
-                        to_usb_interface(hub->intfdev)->pm_usage_cnt = 1;
+                        atomic_set(&to_usb_interface(hub->intfdev)->
+                                        pm_usage_cnt, 1);
                         return;         /* Continues at init2: below */
                 } else {
                         hub_power_on(hub, true);
diff --git a/include/linux/usb.h b/include/linux/usb.h
index 3b45a0d27b80..a34fa89f1474 100644
--- a/include/linux/usb.h
+++ b/include/linux/usb.h
@@ -195,7 +195,7 @@ struct usb_interface {
 
         struct device dev;              /* interface specific device info */
         struct device *usb_dev;
-        int pm_usage_cnt;               /* usage counter for autosuspend */
+        atomic_t pm_usage_cnt;          /* usage counter for autosuspend */
         struct work_struct reset_ws;    /* for resets in atomic context */
 };
 #define to_usb_interface(d) container_of(d, struct usb_interface, dev)
@@ -551,13 +551,13 @@ extern void usb_autopm_put_interface_async(struct usb_interface *intf);
 
 static inline void usb_autopm_enable(struct usb_interface *intf)
 {
-        intf->pm_usage_cnt = 0;
+        atomic_set(&intf->pm_usage_cnt, 0);
         usb_autopm_set_interface(intf);
 }
 
 static inline void usb_autopm_disable(struct usb_interface *intf)
 {
-        intf->pm_usage_cnt = 1;
+        atomic_set(&intf->pm_usage_cnt, 1);
         usb_autopm_set_interface(intf);
 }