Re: [RFC PATCH 0/4] async: fix hangs on weakly-ordered architectures

[Ying Fang]

On 2020/4/7 22:07, Paolo Bonzini wrote:
> ARM machines and other weakly-ordered architectures have been suffering
> for a long time from hangs in qemu-img and qemu-io.  For QEMU binaries
> these are mitigated by the timers that sooner or later fire in the main
> loop, but these will not happen for the tools and probably not with I/O
> threads either.
yes, we occasionally see qemu main thread hangs and VM stuck in in-shutdown
state on aarch64 platform. So this could happen with I/O threads.
> The fix is in patch 5.  Patch 1-3 are docs updates that explain the bug,
> and patch 4 is a bugfix exposed by the new patch.
>
> Paolo
>
> Paolo Bonzini (5):
>    atomics: convert to reStructuredText
>    atomics: update documentation
>    rcu: do not mention atomic_mb_read/set in documentation
>    aio-wait: delegate polling of main AioContext if BQL not held
>    async: use explicit memory barriers
>
>   docs/devel/atomics.rst   | 501 +++++++++++++++++++++++++++++++++++++++
>   docs/devel/atomics.txt   | 403 -------------------------------
>   docs/devel/index.rst     |   1 +
>   docs/devel/rcu.txt       |   4 +-
>   include/block/aio-wait.h |  22 ++
>   include/block/aio.h      |  29 +--
>   util/aio-posix.c         |  16 +-
>   util/aio-win32.c         |  17 +-
>   util/async.c             |  16 +-
>   9 files changed, 576 insertions(+), 433 deletions(-)
>   create mode 100644 docs/devel/atomics.rst
>   delete mode 100644 docs/devel/atomics.txt