From ff2f07874362d34684296f2bd5547a099f33c6d4 Mon Sep 17 00:00:00 2001 From: Alan Stern Date: Fri, 25 Jun 2010 14:02:35 -0400 Subject: [PATCH] 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 --- drivers/usb/core/hcd-pci.c | 12 ++++++++++++ drivers/usb/core/hcd.c | 5 ++++- include/linux/usb/hcd.h | 2 ++ 3 files changed, 18 insertions(+), 1 deletion(-) diff --git a/drivers/usb/core/hcd-pci.c b/drivers/usb/core/hcd-pci.c index e387e394f876..352577baa53d 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 f2fe7c8e991d..0358c05e6e8a 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); diff --git a/include/linux/usb/hcd.h b/include/linux/usb/hcd.h index ae10020b4023..3b571f1ffbb3 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? */ -- 2.11.0