From 2c476bab281843c1f2eb8bc37622f27580b506ef Mon Sep 17 00:00:00 2001 From: Mathias Nyman Date: Thu, 15 Jul 2021 18:06:51 +0300 Subject: [PATCH] xhci: Fix lost USB 2 remote wake commit 72f68bf5c756f5ce1139b31daae2684501383ad5 upstream. There's a small window where a USB 2 remote wake may be left unhandled due to a race between hub thread and xhci port event interrupt handler. When the resume event is detected in the xhci interrupt handler it kicks the hub timer, which should move the port from resume to U0 once resume has been signalled for long enough. To keep the hub "thread" running we set a bus_state->resuming_ports flag. This flag makes sure hub timer function kicks itself. checking this flag was not properly protected by the spinlock. Flag was copied to a local variable before lock was taken. The local variable was then checked later with spinlock held. If interrupt is handled right after copying the flag to the local variable we end up stopping the hub thread before it can handle the USB 2 resume. CPU0 CPU1 (hub thread) (xhci event handler) xhci_hub_status_data() status = bus_state->resuming_ports; handle_port_status() spin_lock() bus_state->resuming_ports = 1 set_flag(HCD_FLAG_POLL_RH) spin_unlock() spin_lock() if (!status) clear_flag(HCD_FLAG_POLL_RH) spin_unlock() Fix this by taking the lock a bit earlier so that it covers the resuming_ports flag copy in the hub thread Cc: Signed-off-by: Mathias Nyman Link: https://lore.kernel.org/r/20210715150651.1996099-2-mathias.nyman@linux.intel.com Signed-off-by: Greg Kroah-Hartman --- drivers/usb/host/xhci-hub.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/drivers/usb/host/xhci-hub.c b/drivers/usb/host/xhci-hub.c index e9b18fc176172..151e93c4bd574 100644 --- a/drivers/usb/host/xhci-hub.c +++ b/drivers/usb/host/xhci-hub.c @@ -1638,11 +1638,12 @@ int xhci_hub_status_data(struct usb_hcd *hcd, char *buf) * Inform the usbcore about resume-in-progress by returning * a non-zero value even if there are no status changes. */ + spin_lock_irqsave(&xhci->lock, flags); + status = bus_state->resuming_ports; mask = PORT_CSC | PORT_PEC | PORT_OCC | PORT_PLC | PORT_WRC | PORT_CEC; - spin_lock_irqsave(&xhci->lock, flags); /* For each port, did anything change? If so, set that bit in buf. */ for (i = 0; i < max_ports; i++) { temp = readl(ports[i]->addr);