Re: [PATCH 14/19] util/async: Fixed tsan warnings

[Stefan Hajnoczi]

On Fri, May 22, 2020 at 12:07:50PM -0400, Robert Foley wrote:
> For example:
>   Atomic write of size 8 at 0x7b4800113c28 by main thread (mutexes: write 
> M30):
>     #0 __tsan_atomic64_exchange <null> (qemu-system-aarch64+0x386f85)
>     #1 aio_bh_poll util/async.c:146:5 (qemu-system-aarch64+0xcd1f61)
>     #2 aio_dispatch util/aio-posix.c:380:5 (qemu-system-aarch64+0xcd8abb)
>     #3 aio_ctx_dispatch util/async.c:298:5 (qemu-system-aarch64+0xcd31b0)
>     #4 g_main_context_dispatch <null> (libglib-2.0.so.0+0x4c416)
>     #5 qemu_main_loop softmmu/vl.c:1664:9 (qemu-system-aarch64+0x5cc6d6)
>     #6 main softmmu/main.c:49:5 (qemu-system-aarch64+0xc62857)
> 
>   Previous read of size 8 at 0x7b4800113c28 by thread T3 (mutexes: write M81):
>     #0 aio_bh_enqueue util/async.c:81:9 (qemu-system-aarch64+0xcd2267)
>     #1 qemu_bh_schedule util/async.c:181:5 (qemu-system-aarch64+0xcd2267)
>     #2 worker_thread util/thread-pool.c:113:9 (qemu-system-aarch64+0xcd473c)
>     #3 qemu_thread_start util/qemu-thread-posix.c:519:9 
> (qemu-system-aarch64+0xcde280)
> 
> Cc: Stefan Hajnoczi <address@hidden>
> Cc: Fam Zheng <address@hidden>
> Signed-off-by: Robert Foley <address@hidden>
> ---
>  util/async.c | 11 +++++++++--
>  1 file changed, 9 insertions(+), 2 deletions(-)

Please explain why these warnings should be ignored in the commit
description. I have been CCed on this patch, am unfamiliar with TSAN
annotations, and now need to figure out:
1. Is ignoring the warning safe or should async.c be fixed somehow?
2. How do the annotation macros work and are they being used correectly?

It's likely that people coming across this commit in the future would
also benefit from information in the commit description that makes these
things clear.

Thanks,
Stefan

signature.asc
Description: PGP signature