The system can hit a deadlock if 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")
Signed-off-by: Bill Kuzeja <william.kuzeja@xxxxxxxxxxx>
---
drivers/usb/host/xhci.c | 22 +++++++++++++++++++---
1 file changed, 19 insertions(+), 3 deletions(-)
diff --git a/drivers/usb/host/xhci.c b/drivers/usb/host/xhci.c
index 248cd7a..835708d 100644
--- a/drivers/usb/host/xhci.c
+++ b/drivers/usb/host/xhci.c
@@ -3132,7 +3132,16 @@ 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);
+
+ if (xhci_queue_stop_endpoint(xhci, stop_cmd, udev->slot_id,
+ ep_index, 0) < 0) {
+ spin_unlock_irqrestore(&xhci->lock, flags);
+ xhci_free_command(xhci, cfg_cmd);
+ xhci_warn(xhci, "%s: stop_cmd xhci_queue_stop_endpoint "
+ "returns error, exiting\n", __func__);
+ goto cleanup;
+ }
+
xhci_ring_cmd_db(xhci);
spin_unlock_irqrestore(&xhci->lock, flags);
@@ -3146,8 +3155,15 @@ 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,
- udev->slot_id, false);
+ if (xhci_queue_configure_endpoint(xhci, cfg_cmd, cfg_cmd->in_ctx->dma,
+ udev->slot_id, false) < 0) {
+ spin_unlock_irqrestore(&xhci->lock, flags);
+ xhci_free_command(xhci, cfg_cmd);
+ xhci_warn(xhci, "%s: cfg_cmd xhci_queue_configure_endpoint "
+ "returns error, exiting\n", __func__);
+ goto cleanup;
+ }
+
xhci_ring_cmd_db(xhci);
spin_unlock_irqrestore(&xhci->lock, flags);
--
1.8.3.1
