xhci: Fix race related to abort operation
commit 1c111b6c 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>
Showing
Please register or sign in to comment