This is a note to let you know that I've just added the patch titled
xhci: Fix lost USB 2 remote wake
to my usb git tree which can be found at git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/usb.git in the usb-linus branch.
The patch will show up in the next release of the linux-next tree (usually sometime within the next 24 hours during the week.)
The patch will hopefully also be merged in Linus's tree for the next -rc kernel release.
If you have any questions about this process, please let me know.
From 72f68bf5c756f5ce1139b31daae2684501383ad5 Mon Sep 17 00:00:00 2001
From: Mathias Nyman mathias.nyman@linux.intel.com Date: Thu, 15 Jul 2021 18:06:51 +0300 Subject: xhci: Fix lost USB 2 remote wake
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; <Interrupt> 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: stable@vger.kernel.org Signed-off-by: Mathias Nyman mathias.nyman@linux.intel.com Link: https://lore.kernel.org/r/20210715150651.1996099-2-mathias.nyman@linux.intel... Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- 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 e9b18fc17617..151e93c4bd57 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);