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| author | Alan Stern <stern@rowland.harvard.edu> | 2007-10-11 16:47:36 -0400 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@suse.de> | 2007-10-12 14:55:35 -0700 |
| commit | d1aa3e6aa8edfeb864af7c930523d9e588b28bea (patch) | |
| tree | 1ad0e6ead73cccc43dd1c1997aabb25acb4970d2 /drivers | |
| parent | 58ed7b94d98245fbad54a0af7ea3317ab1dd6876 (diff) | |
| download | linux-d1aa3e6aa8edfeb864af7c930523d9e588b28bea.tar.bz2 | |
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 <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Diffstat (limited to 'drivers')
| -rw-r--r-- | drivers/usb/core/driver.c | 32 |
1 files changed, 16 insertions, 16 deletions
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. |