From d1aa3e6aa8edfeb864af7c930523d9e588b28bea Mon Sep 17 00:00:00 2001 From: Alan Stern Date: Thu, 11 Oct 2007 16:47:36 -0400 Subject: USB: fix race in autosuspend reschedule This patch (as1002) fixes a small race which can occur when a driver expects usbcore to reschedule an autosuspend request. If the request arrives too late, it won't be rescheduled. The patch adds an extra argument to autosuspend_check(), indicating that a reschedule is needed no matter how much time has elapsed. It also tries to avoid letting asynchronous changes to the value of jiffies cause a delay to become negative, by caching a local copy of the current time. Signed-off-by: Alan Stern Signed-off-by: Greg Kroah-Hartman --- drivers/usb/core/driver.c | 32 ++++++++++++++++---------------- 1 file changed, 16 insertions(+), 16 deletions(-) (limited to 'drivers/usb') diff --git a/drivers/usb/core/driver.c b/drivers/usb/core/driver.c index 8c1eac27f2de..c27bc080d84e 100644 --- a/drivers/usb/core/driver.c +++ b/drivers/usb/core/driver.c @@ -950,11 +950,11 @@ done: #ifdef CONFIG_USB_SUSPEND /* Internal routine to check whether we may autosuspend a device. */ -static int autosuspend_check(struct usb_device *udev) +static int autosuspend_check(struct usb_device *udev, int reschedule) { int i; struct usb_interface *intf; - unsigned long suspend_time; + unsigned long suspend_time, j; /* For autosuspend, fail fast if anything is in use or autosuspend * is disabled. Also fail if any interfaces require remote wakeup @@ -996,20 +996,20 @@ static int autosuspend_check(struct usb_device *udev) } /* If everything is okay but the device hasn't been idle for long - * enough, queue a delayed autosuspend request. + * enough, queue a delayed autosuspend request. If the device + * _has_ been idle for long enough and the reschedule flag is set, + * likewise queue a delayed (1 second) autosuspend request. */ - if (time_after(suspend_time, jiffies)) { + j = jiffies; + if (time_before(j, suspend_time)) + reschedule = 1; + else + suspend_time = j + HZ; + if (reschedule) { if (!timer_pending(&udev->autosuspend.timer)) { - - /* The value of jiffies may change between the - * time_after() comparison above and the subtraction - * below. That's okay; the system behaves sanely - * when a timer is registered for the present moment - * or for the past. - */ queue_delayed_work(ksuspend_usb_wq, &udev->autosuspend, - round_jiffies_relative(suspend_time - jiffies)); - } + round_jiffies_relative(suspend_time - j)); + } return -EAGAIN; } return 0; @@ -1017,7 +1017,7 @@ static int autosuspend_check(struct usb_device *udev) #else -static inline int autosuspend_check(struct usb_device *udev) +static inline int autosuspend_check(struct usb_device *udev, int reschedule) { return 0; } @@ -1074,7 +1074,7 @@ static int usb_suspend_both(struct usb_device *udev, pm_message_t msg) udev->do_remote_wakeup = device_may_wakeup(&udev->dev); if (udev->auto_pm) { - status = autosuspend_check(udev); + status = autosuspend_check(udev, 0); if (status < 0) goto done; } @@ -1100,7 +1100,7 @@ static int usb_suspend_both(struct usb_device *udev, pm_message_t msg) /* Try another autosuspend when the interfaces aren't busy */ if (udev->auto_pm) - autosuspend_check(udev); + autosuspend_check(udev, status == -EBUSY); /* If the suspend succeeded then prevent any more URB submissions, * flush any outstanding URBs, and propagate the suspend up the tree. -- cgit v1.2.3