AioContext: acquire/release AioContext during aio_poll

This is the first step in pushing down acquire/release, and will let
rfifolock drop the contention callback feature.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Message-id: 1424449612-18215-3-git-send-email-pbonzini@redhat.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

1 files changed, 7 insertions, 6 deletions

diff --git a/include/block/aio.h b/include/block/aio.h
index 0dc7a258e2..d2bb423de1 100644
--- a/include/block/aio.h
+++ b/include/block/aio.h
@@ -118,13 +118,14 @@ void aio_context_ref(AioContext *ctx);
 void aio_context_unref(AioContext *ctx);
 
 /* Take ownership of the AioContext.  If the AioContext will be shared between
- * threads, a thread must have ownership when calling aio_poll().
+ * threads, and a thread does not want to be interrupted, it will have to
+ * take ownership around calls to aio_poll().  Otherwise, aio_poll()
+ * automatically takes care of calling aio_context_acquire and
+ * aio_context_release.
  *
- * Note that multiple threads calling aio_poll() means timers, BHs, and
- * callbacks may be invoked from a different thread than they were registered
- * from.  Therefore, code must use AioContext acquire/release or use
- * fine-grained synchronization to protect shared state if other threads will
- * be accessing it simultaneously.
+ * Access to timers and BHs from a thread that has not acquired AioContext
+ * is possible.  Access to callbacks for now must be done while the AioContext
+ * is owned by the thread (FIXME).
  */
 void aio_context_acquire(AioContext *ctx);