On 12/20/2016 02:34 AM, Paolo Valente wrote:

quoted

Il giorno 17 dic 2016, alle ore 01:12, Jens Axboe [off-list ref] ha scritto:

This is basically identical to deadline-iosched, except it registers
as a MQ capable scheduler. This is still a single queue design.

Signed-off-by: Jens Axboe <axboe@fb.com>
...
+
+static bool dd_has_work(struct blk_mq_hw_ctx *hctx)
+{
+	struct deadline_data *dd = hctx->queue->elevator->elevator_data;
+
+	return !list_empty_careful(&dd->dispatch) ||
+		!list_empty_careful(&dd->fifo_list[0]) ||
+		!list_empty_careful(&dd->fifo_list[1]);

Just a request for clarification: if I'm not mistaken,
list_empty_careful can be used safely only if the only possible other
concurrent access is a delete.  Or am I missing something?

We can "solve" that with memory barriers. For now, it's safe to ignore
on your end.


-- 
Jens Axboe