+ // one immediately and kick it started.
+ // NOTE: Possible race condition between blkio_commit and pwait.
+ // Consider: what if scheduler complete the request before pwait even get
+ // called?
+ // Two possible work around:
+ // #1. we disable the interrupt before schedule the request.
+ // #2. we do scheduling within interrupt context (e.g., attach a timer)
+ // As we don't want to overwhelming the interrupt context and also keep the
+ // request RTT as small as possible, hence #1 is preferred.
+