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authorAlan Stern <stern@rowland.harvard.edu>2010-06-25 14:02:35 -0400
committerGreg Kroah-Hartman <gregkh@suse.de>2010-08-10 14:35:38 -0700
commitff2f07874362d34684296f2bd5547a099f33c6d4 (patch)
treef41b8c3fcdd0556f4542058433d82f260928727d /drivers/usb/core
parentee0b9be829803e3ff5adec7456bd59a08425ffa1 (diff)
downloadop-kernel-dev-ff2f07874362d34684296f2bd5547a099f33c6d4.zip
op-kernel-dev-ff2f07874362d34684296f2bd5547a099f33c6d4.tar.gz
USB: fix race between root-hub wakeup & controller suspend
This patch (as1395) adds code to hcd_pci_suspend() for handling wakeup races. This is another general race pattern, similar to the "open vs. unregister" race we're all familiar with. Here, the race is between suspending a device and receiving a wakeup request from one of the device's suspended children. In particular, if a root-hub wakeup is requested at about the same time as the corresponding USB controller is suspended, and if the controller is enabled for wakeup, then the controller should either fail to suspend or else wake right back up again. During system sleep this won't happen very much, especially since host controllers generally aren't enabled for wakeup during sleep. However it is definitely an issue for runtime PM. Something like this will be needed to prevent the controller from autosuspending while waiting for a root-hub resume to take place. (That is, in fact, the common case, for which there is an extra test.) Signed-off-by: Alan Stern <stern@rowland.harvard.edu> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Diffstat (limited to 'drivers/usb/core')
-rw-r--r--drivers/usb/core/hcd-pci.c12
-rw-r--r--drivers/usb/core/hcd.c5
2 files changed, 16 insertions, 1 deletions
diff --git a/drivers/usb/core/hcd-pci.c b/drivers/usb/core/hcd-pci.c
index e387e39..352577b 100644
--- a/drivers/usb/core/hcd-pci.c
+++ b/drivers/usb/core/hcd-pci.c
@@ -388,8 +388,20 @@ static int hcd_pci_suspend(struct device *dev)
if (hcd->driver->pci_suspend) {
bool do_wakeup = device_may_wakeup(dev);
+ /* Optimization: Don't suspend if a root-hub wakeup is
+ * pending and it would cause the HCD to wake up anyway.
+ */
+ if (do_wakeup && HCD_WAKEUP_PENDING(hcd))
+ return -EBUSY;
retval = hcd->driver->pci_suspend(hcd, do_wakeup);
suspend_report_result(hcd->driver->pci_suspend, retval);
+
+ /* Check again in case wakeup raced with pci_suspend */
+ if (retval == 0 && do_wakeup && HCD_WAKEUP_PENDING(hcd)) {
+ if (hcd->driver->pci_resume)
+ hcd->driver->pci_resume(hcd, false);
+ retval = -EBUSY;
+ }
if (retval)
return retval;
}
diff --git a/drivers/usb/core/hcd.c b/drivers/usb/core/hcd.c
index f2fe7c8..0358c05 100644
--- a/drivers/usb/core/hcd.c
+++ b/drivers/usb/core/hcd.c
@@ -1940,6 +1940,7 @@ int hcd_bus_resume(struct usb_device *rhdev, pm_message_t msg)
dev_dbg(&rhdev->dev, "usb %s%s\n",
(msg.event & PM_EVENT_AUTO ? "auto-" : ""), "resume");
+ clear_bit(HCD_FLAG_WAKEUP_PENDING, &hcd->flags);
if (!hcd->driver->bus_resume)
return -ENOENT;
if (hcd->state == HC_STATE_RUNNING)
@@ -1993,8 +1994,10 @@ void usb_hcd_resume_root_hub (struct usb_hcd *hcd)
unsigned long flags;
spin_lock_irqsave (&hcd_root_hub_lock, flags);
- if (hcd->rh_registered)
+ if (hcd->rh_registered) {
+ set_bit(HCD_FLAG_WAKEUP_PENDING, &hcd->flags);
queue_work(pm_wq, &hcd->wakeup_work);
+ }
spin_unlock_irqrestore (&hcd_root_hub_lock, flags);
}
EXPORT_SYMBOL_GPL(usb_hcd_resume_root_hub);
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