Re: BUG #16990: Random PANIC in qemu user context

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Paul Guyot <pguyot(at)kallisys(dot)net>
Cc: pgsql-bugs(at)lists(dot)postgresql(dot)org
Subject: Re: BUG #16990: Random PANIC in qemu user context
Date: 2021-05-02 22:19:58
Message-ID: 3723542.1619993998@sss.pgh.pa.us
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Paul Guyot <pguyot(at)kallisys(dot)net> writes:
> QEMU user emulation documentation mentions something specific to threading on ARM.
> https://qemu.readthedocs.io/en/latest/user/main.html
>> Threading:
>> On Linux, QEMU can emulate the clone syscall and create a real host thread (with a separate virtual CPU) for each emulated thread. Note that not all targets currently emulate atomic operations correctly. x86 and Arm use a global lock in order to preserve their semantics.

Oooh, that's pretty suggestive. I wonder just when that "global lock" is
taken or released. Maybe the timing of it is such that it interferes
with ever seeing our lock as free?

regards, tom lane

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