coroutine: simplify co_aio_sleep_ns() prototype

The AioContext pointer argument to co_aio_sleep_ns() is only used for
the sleep timer.  It does not affect where the caller coroutine is
resumed.

Due to changes to coroutine and AIO APIs it is now possible to drop the
AioContext pointer argument.  This is safe to do since no caller has
specific requirements for which AioContext the timer must run in.

This patch drops the AioContext pointer argument and renames the
function to simplify the API.
Reported-by: NPaolo Bonzini <pbonzini@redhat.com>
Reported-by: NEric Blake <eblake@redhat.com>
Signed-off-by: NStefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: NEric Blake <eblake@redhat.com>
Message-id: 20171109102652.6360-1-stefanha@redhat.com
Signed-off-by: NStefan Hajnoczi <stefanha@redhat.com>

block/null.c

@@ -110,8 +110,7 @@ static coroutine_fn int null_co_common(BlockDriverState *bs)
     BDRVNullState *s = bs->opaque;
 
     if (s->latency_ns) {
-        co_aio_sleep_ns(bdrv_get_aio_context(bs), QEMU_CLOCK_REALTIME,
-                        s->latency_ns);
+        qemu_co_sleep_ns(QEMU_CLOCK_REALTIME, s->latency_ns);
     }
     return 0;
 }

block/sheepdog.c

@@ -776,8 +776,7 @@ static coroutine_fn void reconnect_to_sdog(void *opaque)
         if (s->fd < 0) {
             DPRINTF("Wait for connection to be established\n");
             error_report_err(local_err);
-            co_aio_sleep_ns(bdrv_get_aio_context(s->bs), QEMU_CLOCK_REALTIME,
-                            1000000000ULL);
+            qemu_co_sleep_ns(QEMU_CLOCK_REALTIME, 1000000000ULL);
         }
     };
 

include/qemu/coroutine.h

@@ -261,12 +261,8 @@ void qemu_co_rwlock_unlock(CoRwlock *lock);
 
 /**
  * Yield the coroutine for a given duration
- *
- * Behaves similarly to co_sleep_ns(), but the sleeping coroutine will be
- * resumed when using aio_poll().
  */
-void coroutine_fn co_aio_sleep_ns(AioContext *ctx, QEMUClockType type,
-                                  int64_t ns);
+void coroutine_fn qemu_co_sleep_ns(QEMUClockType type, int64_t ns);
 
 /**
  * Yield until a file descriptor becomes readable

util/qemu-coroutine-sleep.c

@@ -31,9 +31,9 @@ static void co_sleep_cb(void *opaque)
     aio_co_wake(sleep_cb->co);
 }
 
-void coroutine_fn co_aio_sleep_ns(AioContext *ctx, QEMUClockType type,
-                                  int64_t ns)
+void coroutine_fn qemu_co_sleep_ns(QEMUClockType type, int64_t ns)
 {
+    AioContext *ctx = qemu_get_current_aio_context();
     CoSleepCB sleep_cb = {
         .co = qemu_coroutine_self(),
     };