On 01/07/2015 16:59, Stefan Hajnoczi wrote: > I found it annoying to write it backwards too, but it's for consistency: > > if (s->buf_free_count < nb_chunks + added_chunks) { > trace_mirror_break_buf_busy(s, nb_chunks, s->in_flight); > break; > } > if (IOV_MAX < nb_chunks + added_chunks) { > trace_mirror_break_iov_max(s, nb_chunks, added_chunks); > break; > } > > It's the same type of check as s->buf_free_count (which isn't modified > by this loop either so it's a yoda conditional).
Hmm, right. The problem goes back to: while (nb_chunks == 0 && s->buf_free_count < added_chunks) { trace_mirror_yield_buf_busy(s, nb_chunks, s->in_flight); qemu_coroutine_yield(); } where s->buf_free_count _is_ modified by the loop. The if below: if (s->buf_free_count < nb_chunks + added_chunks) { trace_mirror_break_buf_busy(s, nb_chunks, s->in_flight); break; } is written as a < check for consistency, and the one you add exacerbates the problem. If you want you can change the < to > in the "while" loop as well; otherwise the patch is okay as is. Paolo