From ff2f07874362d34684296f2bd5547a099f33c6d4 Mon Sep 17 00:00:00 2001 From: Alan Stern Date: Fri, 25 Jun 2010 14:02:35 -0400 Subject: 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 Signed-off-by: Greg Kroah-Hartman --- include/linux/usb/hcd.h | 2 ++ 1 file changed, 2 insertions(+) (limited to 'include/linux/usb') diff --git a/include/linux/usb/hcd.h b/include/linux/usb/hcd.h index ae10020b402..3b571f1ffbb 100644 --- a/include/linux/usb/hcd.h +++ b/include/linux/usb/hcd.h @@ -98,6 +98,7 @@ struct usb_hcd { #define HCD_FLAG_SAW_IRQ 1 #define HCD_FLAG_POLL_RH 2 /* poll for rh status? */ #define HCD_FLAG_POLL_PENDING 3 /* status has changed? */ +#define HCD_FLAG_WAKEUP_PENDING 4 /* root hub is resuming? */ /* The flags can be tested using these macros; they are likely to * be slightly faster than test_bit(). @@ -106,6 +107,7 @@ struct usb_hcd { #define HCD_SAW_IRQ(hcd) ((hcd)->flags & (1U << HCD_FLAG_SAW_IRQ)) #define HCD_POLL_RH(hcd) ((hcd)->flags & (1U << HCD_FLAG_POLL_RH)) #define HCD_POLL_PENDING(hcd) ((hcd)->flags & (1U << HCD_FLAG_POLL_PENDING)) +#define HCD_WAKEUP_PENDING(hcd) ((hcd)->flags & (1U << HCD_FLAG_WAKEUP_PENDING)) /* Flags that get set only during HCD registration or removal. */ unsigned rh_registered:1;/* is root hub registered? */ -- cgit v1.2.3-70-g09d2