From: "Emilio G. Cota" <cota@braap.org>
To: Peter Maydell <peter.maydell@linaro.org>
Cc: qemu-devel@nongnu.org, "Alex Bennée" <alex.bennee@linaro.org>,
"Richard Henderson" <rth@twiddle.net>
Subject: Re: [Qemu-devel] [PATCH v2] cpu-exec: Exit exclusive region on longjmp from step_atomic
Date: Thu, 2 Nov 2017 13:15:38 -0400 [thread overview]
Message-ID: <20171102171538.GA9433@flamenco> (raw)
In-Reply-To: <1509640536-32160-1-git-send-email-peter.maydell@linaro.org>
On Thu, Nov 02, 2017 at 16:35:36 +0000, Peter Maydell wrote:
> Commit ac03ee5331612e44be narrowed the scope of the exclusive
> region so it only covers when we're executing the TB, not when
> we're generating it. However it missed that there is more than
> one execution path out of cpu_tb_exec -- if the atomic insn
> causes an exception then the code will longjmp out, skipping
> the code to end the exclusive region. This causes QEMU to hang
> the next time the CPU calls start_exclusive(), waiting for
> itself to exit the region.
>
> Move the "end the region" code out to the end of the
> function so that it is run for both normal exit and also
> for exit-via-longjmp. We have to use a volatile bool flag
> to decide whether we need to end the region, because we
> can longjump out of the codegen as well as the execution.
>
> (For some reason this only reproduces for me with a clang
> optimized build, not a gcc debug build.)
>
> Fixes: ac03ee5331612e44beb393df2b578c951d27dc0d
> Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Emilio G. Cota <cota@braap.org>
Good catch, thanks for the fix!
E.
next prev parent reply other threads:[~2017-11-02 17:15 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-11-02 16:35 [Qemu-devel] [PATCH v2] cpu-exec: Exit exclusive region on longjmp from step_atomic Peter Maydell
2017-11-02 16:38 ` no-reply
2017-11-02 16:39 ` Peter Maydell
2017-11-02 17:15 ` Emilio G. Cota [this message]
2017-11-02 20:43 ` Richard Henderson
2017-11-03 7:40 ` Alex Bennée
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