On Fri, 2018-07-27 at 10:46 -0600, Keith Busch wrote:
+AD4- On Fri, Jul 27, 2018 at 09:20:42AM -0700, Bart Van Assche wrote:
+AD4- +AD4- +- ret +AD0- req-+AD4-q-+AD4-mq+AF8-ops-+AD4-timeout(req, reserved)+ADs-
+AD4- +AD4- +- /+ACo-
+AD4- +AD4- +- +ACo- BLK+AF8-EH+AF8-DONT+AF8-RESET+AF8-TIMER means that the block driver either
+AD4- +AD4- +- +ACo- completed the request or still owns the request and will
+AD4- +AD4- +- +ACo- continue processing the timeout asynchronously. In the
+AD4- +AD4- +- +ACo- latter case, if blk+AF8-mq+AF8-complete+AF8-request() was called while
+AD4- +AD4- +- +ACo- the timeout handler was in progress, ignore that call.
+AD4- +AD4- +- +ACo-/
+AD4- +AD4- +- if (ret +AD0APQ- BLK+AF8-EH+AF8-DONT+AF8-RESET+AF8-TIMER)
+AD4- +AD4- +- return+ADs-
+AD4-
+AD4- This is how completions get lost.
The new approach for handling completions that occur while the .timeout()
callback in progress is as follows:
+ACo- blk+AF8-mq+AF8-complete+AF8-request() executes the following code:
if (blk+AF8-mq+AF8-change+AF8-rq+AF8-state(rq, MQ+AF8-RQ+AF8-TIMED+AF8-OUT, MQ+AF8-RQ+AF8-COMPLETE))
return+ADs-
+ACo- blk+AF8-mq+AF8-rq+AF8-timed+AF8-out() executes the following code:
if (blk+AF8-mq+AF8-rq+AF8-state(req) +AD0APQ- MQ+AF8-RQ+AF8-COMPLETE) +AHs-
+AF8AXw-blk+AF8-mq+AF8-complete+AF8-request(req)+ADs-
return+ADs-
+AH0-
As one can see +AF8AXw-blk+AF8-mq+AF8-complete+AF8-request() gets called if this race occurs.
Bart.
