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[Qemu-block] [PATCH v2 2/6] docs: mark nested AioContext locking as a le
From: |
Stefan Hajnoczi |
Subject: |
[Qemu-block] [PATCH v2 2/6] docs: mark nested AioContext locking as a legacy API |
Date: |
Thu, 7 Dec 2017 20:13:16 +0000 |
See the patch for why nested AioContext locking is no longer allowed.
Signed-off-by: Stefan Hajnoczi <address@hidden>
---
docs/devel/multiple-iothreads.txt | 7 ++++---
1 file changed, 4 insertions(+), 3 deletions(-)
diff --git a/docs/devel/multiple-iothreads.txt
b/docs/devel/multiple-iothreads.txt
index e4d340bbb7..4f9012d154 100644
--- a/docs/devel/multiple-iothreads.txt
+++ b/docs/devel/multiple-iothreads.txt
@@ -1,4 +1,4 @@
-Copyright (c) 2014 Red Hat Inc.
+Copyright (c) 2014-2017 Red Hat Inc.
This work is licensed under the terms of the GNU GPL, version 2 or later. See
the COPYING file in the top-level directory.
@@ -92,8 +92,9 @@ aio_context_acquire()/aio_context_release() for mutual
exclusion. Once the
context is acquired no other thread can access it or run event loop iterations
in this AioContext.
-aio_context_acquire()/aio_context_release() calls may be nested. This
-means you can call them if you're not sure whether #2 applies.
+Legacy code sometimes nests aio_context_acquire()/aio_context_release() calls.
+Do not use nesting anymore, it is incompatible with the BDRV_POLL_WHILE() macro
+used in the block layer and can lead to hangs.
There is currently no lock ordering rule if a thread needs to acquire multiple
AioContexts simultaneously. Therefore, it is only safe for code holding the
--
2.14.3
- [Qemu-block] [PATCH v2 0/6] block: avoid recursive AioContext acquire in bdrv_inactivate_all(), Stefan Hajnoczi, 2017/12/07
- [Qemu-block] [PATCH v2 2/6] docs: mark nested AioContext locking as a legacy API,
Stefan Hajnoczi <=
- [Qemu-block] [PATCH v2 1/6] block: avoid recursive AioContext acquire in bdrv_inactivate_all(), Stefan Hajnoczi, 2017/12/07
- [Qemu-block] [PATCH v2 3/6] blockdev: add x-blockdev-set-iothread force boolean, Stefan Hajnoczi, 2017/12/07
- [Qemu-block] [PATCH v2 4/6] iotests: add VM.add_object(), Stefan Hajnoczi, 2017/12/07
- [Qemu-block] [PATCH v2 5/6] iothread: fix iothread_stop() race condition, Stefan Hajnoczi, 2017/12/07
- [Qemu-block] [PATCH v2 6/6] qemu-iotests: add 203 savevm with IOThreads test, Stefan Hajnoczi, 2017/12/07