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From: Richard Henderson <rth@twiddle.net>
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Date: Mon, 25 Apr 2016 21:48:16 -0700
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Subject: Re: [Qemu-devel] [RFC v3] translate-all: protect code_gen_buffer
 with RCU
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To: "Emilio G. Cota" <cota@braap.org>, QEMU Developers <qemu-devel@nongnu.org>, MTTCG Devel <mttcg@greensocs.com>
Cc: =?UTF-8?Q?Alex_Benn=c3=a9e?= <alex.bennee@linaro.org>, Paolo Bonzini <pbonzini@redhat.com>, Peter Crosthwaite <crosthwaite.peter@gmail.com>, Sergey Fedorov <serge.fdrv@gmail.com>

On 04/25/2016 04:46 PM, Emilio G. Cota wrote:
> +    /*
> +     * write the prologue into buf2. This is safe because we'll later call
> +     * tcg_prologue_init on buf1, from which we'll start execution.
> +     */
> +    tcg_ctx.code_gen_buffer = code_gen_buf2;
> +    tcg_prologue_init(&tcg_ctx);
> +

Ah, no.  Write only one prologue, not one per buffer.

If they're sufficiently close (i.e. one allocation under the max size),
then the same one can be used for both halves.

The global variables that you didn't see in this revision are:

aarch64/tcg-target.inc.c:static tcg_insn_unit *tb_ret_addr;
arm/tcg-target.inc.c:static tcg_insn_unit *tb_ret_addr;
i386/tcg-target.inc.c:static tcg_insn_unit *tb_ret_addr;
ia64/tcg-target.inc.c:static tcg_insn_unit *tb_ret_addr;
ia64/tcg-target.inc.c:    tcg_insn_unit *thunks[8] = { };
mips/tcg-target.inc.c:static tcg_insn_unit *tb_ret_addr;
ppc/tcg-target.inc.c:static tcg_insn_unit *tb_ret_addr;
s390/tcg-target.inc.c:static tcg_insn_unit *tb_ret_addr;
sparc/tcg-target.inc.c:static tcg_insn_unit *qemu_ld_trampoline[16];
sparc/tcg-target.inc.c:static tcg_insn_unit *qemu_st_trampoline[16];


r~