From: Bill Kuzeja William.Kuzeja@stratus.com

The system can hit a deadlock if an xhci adapter breaks while initializing. The deadlock is between two threads: thread 1 is tearing down the adapter and is stuck in usb_unlocked_disable_lpm waiting to lock the hcd->handwidth_mutex. Thread 2 is holding this mutex (while still trying to add a usb device), but is stuck in xhci_endpoint_reset waiting for a stop or config command to complete. A reboot is required to resolve.

It turns out when calling xhci_queue_stop_endpoint and xhci_queue_configure_endpoint in xhci_endpoint_reset, the return code is not checked for errors. If the timing is right and the adapter dies just before either of these commands get issued, we hang indefinitely waiting for a completion on a command that didn't get issued.

This wasn't a problem before the following fix because we didn't send commands in xhci_endpoint_reset:

commit f5249461b504 ("xhci: Clear the host side toggle manually when endpoint is soft reset")

With the patch I am submitting, a duration test which breaks adapters during initialization (and which deadlocks with the standard kernel) runs without issue.

Fixes: f5249461b504 ("xhci: Clear the host side toggle manually when endpoint is soft reset") Cc: stable@vger.kernel.org # v4.17+ Cc: Torez Smith torez@redhat.com Signed-off-by: Bill Kuzeja william.kuzeja@stratus.com Signed-off-by: Torez Smith torez@redhat.com Signed-off-by: Mathias Nyman mathias.nyman@linux.intel.com --- drivers/usb/host/xhci.c | 23 +++++++++++++++++++++-- 1 file changed, 21 insertions(+), 2 deletions(-)

diff --git a/drivers/usb/host/xhci.c b/drivers/usb/host/xhci.c index fe8f9ff58015..8c068d0cc7c1 100644 --- a/drivers/usb/host/xhci.c +++ b/drivers/usb/host/xhci.c @@ -3095,6 +3095,7 @@ static void xhci_endpoint_reset(struct usb_hcd *hcd, unsigned int ep_index; unsigned long flags; u32 ep_flag; + int err;

xhci = hcd_to_xhci(hcd); if (!host_ep->hcpriv) @@ -3154,7 +3155,17 @@ static void xhci_endpoint_reset(struct usb_hcd *hcd, xhci_free_command(xhci, cfg_cmd); goto cleanup; } - xhci_queue_stop_endpoint(xhci, stop_cmd, udev->slot_id, ep_index, 0); + + err = xhci_queue_stop_endpoint(xhci, stop_cmd, udev->slot_id, + ep_index, 0); + if (err < 0) { + spin_unlock_irqrestore(&xhci->lock, flags); + xhci_free_command(xhci, cfg_cmd); + xhci_dbg(xhci, "%s: Failed to queue stop ep command, %d ", + __func__, err); + goto cleanup; + } + xhci_ring_cmd_db(xhci); spin_unlock_irqrestore(&xhci->lock, flags);

@@ -3168,8 +3179,16 @@ static void xhci_endpoint_reset(struct usb_hcd *hcd, ctrl_ctx, ep_flag, ep_flag); xhci_endpoint_copy(xhci, cfg_cmd->in_ctx, vdev->out_ctx, ep_index);

- xhci_queue_configure_endpoint(xhci, cfg_cmd, cfg_cmd->in_ctx->dma, + err = xhci_queue_configure_endpoint(xhci, cfg_cmd, cfg_cmd->in_ctx->dma, udev->slot_id, false); + if (err < 0) { + spin_unlock_irqrestore(&xhci->lock, flags); + xhci_free_command(xhci, cfg_cmd); + xhci_dbg(xhci, "%s: Failed to queue config ep command, %d ", + __func__, err); + goto cleanup; + } + xhci_ring_cmd_db(xhci); spin_unlock_irqrestore(&xhci->lock, flags);