xhci: Fix race related to abort operation
commit 1c111b6c3844a142e03bcfc2fa17bfbdea08e9dc upstream.
Current abort operation has race.
xhci_handle_command_timeout()
xhci_abort_cmd_ring()
xhci_write_64(CMD_RING_ABORT)
xhci_handshake(5s)
do {
check CMD_RING_RUNNING
udelay(1)
...
COMP_CMD_ABORT event
COMP_CMD_STOP event
xhci_handle_stopped_cmd_ring()
restart cmd_ring
CMD_RING_RUNNING become 1 again
} while ()
return -ETIMEDOUT
xhci_write_64(CMD_RING_ABORT)
/* can abort random command */
To do abort operation correctly, we have to wait both of COMP_CMD_STOP
event and negation of CMD_RING_RUNNING.
But like above, while timeout handler is waiting negation of
CMD_RING_RUNNING, event handler can restart cmd_ring. So timeout
handler never be notice negation of CMD_RING_RUNNING, and retry of
CMD_RING_ABORT can abort random command (BTW, I guess retry of
CMD_RING_ABORT was workaround of this race).
To fix this race, this moves xhci_handle_stopped_cmd_ring() to
xhci_abort_cmd_ring(). And timeout handler waits COMP_CMD_STOP event.
At this point, timeout handler is owner of cmd_ring, and safely
restart cmd_ring by using xhci_handle_stopped_cmd_ring().
[FWIW, as bonus, this way would be easily extend to add CMD_RING_PAUSE
operation]
[locks edited as patch is rebased on other locking fixes -Mathias]
Signed-off-by: OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>
Signed-off-by: Mathias Nyman <mathias.nyman@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
diff --git a/drivers/usb/host/xhci-mem.c b/drivers/usb/host/xhci-mem.c
index baba11b..7064892 100644
--- a/drivers/usb/host/xhci-mem.c
+++ b/drivers/usb/host/xhci-mem.c
@@ -2379,6 +2379,7 @@
/* init command timeout work */
INIT_DELAYED_WORK(&xhci->cmd_timer, xhci_handle_command_timeout);
+ init_completion(&xhci->cmd_ring_stop_completion);
page_size = readl(&xhci->op_regs->page_size);
xhci_dbg_trace(xhci, trace_xhci_dbg_init,