Commit 8de66b0e authored Oct 04, 2019 by Bill Kuzeja Committed by Greg Kroah-Hartman Oct 04, 2019

xhci: Prevent deadlock when xhci adapter breaks during init



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 f5249461 ("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: f5249461 ("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>
Link: https://lore.kernel.org/r/1570190373-30684-7-git-send-email-mathias.nyman@linux.intel.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

parent a70bcbc3

drivers/usb/host/xhci.c

+21 −2

Original line number	Diff line number	Diff line
		@@ -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);

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