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Date: Mon, 26 Mar 2012 18:23:58 +0100
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From: Peter Maydell <peter.maydell@linaro.org>
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Subject: Re: [Qemu-devel] [PATCH] sh4-linux-user: fix multi-threading
	regression.
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To: =?UTF-8?Q?C=C3=A9dric_VINCENT?= <cedric.vincent@st.com>
Cc: Riku Voipio <riku.voipio@iki.fi>, qemu-devel <qemu-devel@nongnu.org>, Aurelien Jarno <aurelien@aurel32.net>

2012/3/26 C=C3=A9dric VINCENT <cedric.vincent@st.com>:
> This reverts commit fd4bab10 "target-sh4: optimize exceptions":

[cc'ing Aurelien as the author of that commit]

> the function cpu_restore_state() isn't expected to be called in user-mode=
,

Is this really true? host_signal_handler() calls cpu_signal_handler()
calls handle_cpu_signala) calls cpu_restore_state() so hopefully
it's OK to be called in at least *some* situations...

> as a consequence it isn't protected from race conditions. =C2=A0For
> information, syscalls are exceptions on Linux/SH4.
>
> There were two possible fixes: either "tb_lock" is acquired/released
> around the call to cpu_restore_state() [1] or the commit that
> introduced this regression is reverted [2].

Can you explain a bit further what the race condition is that occurs
here?

NB the whole tb_lock thing is broken anyway.

thanks
-- PMM