Skip to contentSkip to conversation

aio-posix: Fix return value of aio_poll()

PATCH Applied Kevin Wolf 2 participants 3 messages Jan 16, 2013 – Jan 17, 2013

lore
Share & tools
lore

Kevin Wolf

author
#0 lore raw

PATCH v2 1/1 aio-posix: Fix return value of aio_poll()

aio_poll() must return true if any work is still pending, even if it didn't make progress, so that bdrv_drain_all() doesn't stop waiting too early. The possibility of stopping early occasionally lead to a failed assertion in bdrv_drain_all(), when some in-flight request was missed and the function didn't really drain all requests.

In order to make that change, the return value as specified in the function comment must change for blocking = false; fortunately, the return value of blocking = false callers is only used in test cases, so this change shouldn't cause any trouble.

Cc [email protected]
Signed-off-by Kevin Wolf <[email protected]>
---
 aio-posix.c         |    3 ++-
 aio-win32.c         |    3 ++-
 include/block/aio.h |    6 ++----
 tests/test-aio.c    |    4 ++--
 4 files changed, 8 insertions(+), 8 deletions(-)
aio-posix.c +2 -1
index 88d09e1..fe4dbb4 100644
@@ -264,5 +264,6 @@ bool aio_poll(AioContext *ctx, bool blocking)
         }
     }
 
-    return progress;
+    assert(progress || busy);
+    return true;
 }
aio-win32.c +2 -1
index f5ea027..38723bf 100644
@@ -214,5 +214,6 @@ bool aio_poll(AioContext *ctx, bool blocking)
         events[ret - WAIT_OBJECT_0] = events[--count];
     }
 
-    return progress;
+    assert(progress || busy);
+    return true;
 }
include/block/aio.h +2 -4
index 0933f05..8eda924 100644
@@ -173,16 +173,14 @@ bool aio_pending(AioContext *ctx);
  * aio as a result of executing I/O completion or bh callbacks.
  *
  * If there is no pending AIO operation or completion (bottom half),
- * return false.  If there are pending bottom halves, return true.
+ * return false.  If there are pending AIO operations of bottom halves,
+ * return true.
  *
  * If there are no pending bottom halves, but there are pending AIO
  * operations, it may not be possible to make any progress without
  * blocking.  If @blocking is true, this function will wait until one
  * or more AIO events have completed, to ensure something has moved
  * before returning.
- *
- * If @blocking is false, this function will also return false if the
- * function cannot make any progress without blocking.
  */
 bool aio_poll(AioContext *ctx, bool blocking);
tests/test-aio.c +2 -2
index e4ebef7..c173870 100644
@@ -315,13 +315,13 @@ static void test_wait_event_notifier_noflush(void)
     event_notifier_set(&data.e);
     g_assert(aio_poll(ctx, false));
     g_assert_cmpint(data.n, ==, 1);
-    g_assert(!aio_poll(ctx, false));
+    g_assert(aio_poll(ctx, false));
     g_assert_cmpint(data.n, ==, 1);
 
     event_notifier_set(&data.e);
     g_assert(aio_poll(ctx, false));
     g_assert_cmpint(data.n, ==, 2);
-    g_assert(!aio_poll(ctx, false));
+    g_assert(aio_poll(ctx, false));
     g_assert_cmpint(data.n, ==, 2);
 
     event_notifier_set(&dummy.e);
Signature · 1 line
1.7.6.5
author
#1 lore raw

Am 16.01.2013 19:25, schrieb Kevin Wolf:

Quoted 6 lines

aio_poll() must return true if any work is still pending, even if it didn't make progress, so that bdrv_drain_all() doesn't stop waiting too early. The possibility of stopping early occasionally lead to a failed assertion in bdrv_drain_all(), when some in-flight request was missed and the function didn't really drain all requests.

Quoted 7 lines

In order to make that change, the return value as specified in the function comment must change for blocking = false; fortunately, the return value of blocking = false callers is only used in test cases, so this change shouldn't cause any trouble.

Cc [email protected]
Signed-off-by Kevin Wolf <[email protected]>

Argh, sent the wrong file. Stefan, can you please replace "aio-posix" by "aio" in the subject line before applying?

Kevin

Applied
#2 lore raw
In reply to Kevin Wolf
Quoted 11 lines · Kevin Wolf

aio_poll() must return true if any work is still pending, even if it didn't make progress, so that bdrv_drain_all() doesn't stop waiting too early. The possibility of stopping early occasionally lead to a failed assertion in bdrv_drain_all(), when some in-flight request was missed and the function didn't really drain all requests.

In order to make that change, the return value as specified in the function comment must change for blocking = false; fortunately, the return value of blocking = false callers is only used in test cases, so this change shouldn't cause any trouble.

Quoted 8 lines
Cc [email protected]
Signed-off-by Kevin Wolf <[email protected]>
---
 aio-posix.c         |    3 ++-
 aio-win32.c         |    3 ++-
 include/block/aio.h |    6 ++----
 tests/test-aio.c    |    4 ++--
 4 files changed, 8 insertions(+), 8 deletions(-)

Changed "aio-posix" to "aio" in commit message.

Thanks, applied to my block tree:
https://github.com/stefanha/qemu/commits/block

Stefan