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Diffstat (limited to 'docs/devel/multiple-iothreads.txt')
| -rw-r--r-- | docs/devel/multiple-iothreads.txt | 7 |
1 files 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 |