From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:59733) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1bNdH7-0000Kh-3U for qemu-devel@nongnu.org; Thu, 14 Jul 2016 05:49:46 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1bNdH2-0003tI-VW for qemu-devel@nongnu.org; Thu, 14 Jul 2016 05:49:44 -0400 Received: from mail-wm0-x231.google.com ([2a00:1450:400c:c09::231]:37562) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1bNdH2-0003t2-Bm for qemu-devel@nongnu.org; Thu, 14 Jul 2016 05:49:40 -0400 Received: by mail-wm0-x231.google.com with SMTP id i5so106095629wmg.0 for ; Thu, 14 Jul 2016 02:49:39 -0700 (PDT) References: <1467839703-11733-1-git-send-email-sergey.fedorov@linaro.org> <1467839703-11733-12-git-send-email-sergey.fedorov@linaro.org> <8737nc627d.fsf@linaro.org> <57875345.8020501@gmail.com> From: Alex =?utf-8?Q?Benn=C3=A9e?= In-reply-to: <57875345.8020501@gmail.com> Date: Thu, 14 Jul 2016 10:49:41 +0100 Message-ID: <871t2w5z2i.fsf@linaro.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit Subject: Re: [Qemu-devel] [RFC v2 11/11] tcg: Make tb_flush() thread safe List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Sergey Fedorov Cc: Sergey Fedorov , qemu-devel@nongnu.org, MTTCG Devel , KONRAD =?utf-8?B?RnLDqWTDqXJpYw==?= , Alvise Rigo , "Emilio G. Cota" , Paolo Bonzini , Richard Henderson , Peter Maydell , Peter Crosthwaite Sergey Fedorov writes: > On 14/07/16 11:41, Alex Bennée wrote: >> Sergey Fedorov writes: >> >>> From: Sergey Fedorov >>> >>> Use async_safe_run_on_cpu() to make tb_flush() thread safe. >>> >>> Signed-off-by: Sergey Fedorov >>> Signed-off-by: Sergey Fedorov >>> --- >>> >>> Changes in v2: >>> - stale comment about unsafe tb_flush() removed >>> --- >>> translate-all.c | 13 ++++++++----- >>> 1 file changed, 8 insertions(+), 5 deletions(-) >>> >>> diff --git a/translate-all.c b/translate-all.c >>> index eaa95e4cd7dc..e69b5d4e889e 100644 >>> --- a/translate-all.c >>> +++ b/translate-all.c >>> @@ -831,8 +831,7 @@ static void page_flush_tb(void) >>> } >>> >>> /* flush all the translation blocks */ >>> -/* XXX: tb_flush is currently not thread safe */ >>> -void tb_flush(CPUState *cpu) >>> +static void do_tb_flush(CPUState *cpu, void *data) >>> { >>> #if defined(DEBUG_FLUSH) >>> printf("qemu: flush code_size=%ld nb_tbs=%d avg_tb_size=%ld\n", >>> @@ -861,6 +860,11 @@ void tb_flush(CPUState *cpu) >>> tcg_ctx.tb_ctx.tb_flush_count++; >>> } >>> >>> +void tb_flush(CPUState *cpu) >>> +{ >>> + async_safe_run_on_cpu(cpu, do_tb_flush, NULL); >>> +} >>> + >>> #ifdef DEBUG_TB_CHECK >>> >>> static void >>> @@ -1163,9 +1167,8 @@ TranslationBlock *tb_gen_code(CPUState *cpu, >>> buffer_overflow: >>> /* flush must be done */ >>> tb_flush(cpu); >>> - /* cannot fail at this point */ >>> - tb = tb_alloc(pc); >>> - assert(tb != NULL); >>> + mmap_unlock(); >>> + cpu_loop_exit(cpu); >> Given our other discussions about lock resetting I wonder if this is >> another case where mmap_reset() could be called on cpu_loop_exit? > > As I can see, this is the only place mmap_unlock() have to be called > right before cpu_loop_exit(). As I remember, all the other cased in > user-mode emulation were restructured by Peter M. in his syscall/signal > handling series. However, I like the idea to ensure that 'mmap_lock' is > released on any cpu_loop_exit(). What do maintainers think? > > Kind regards, > Sergey > >> >>> } >>> >>> gen_code_buf = tcg_ctx.code_gen_ptr; >> Otherwise so far the testing is looking pretty positive in linux-user: >> >> Tested-by: Alex Bennée >> Reviewed-by: Alex Bennée I should add for the testing to fail without this series I had to apply the hot-path fixes otherwise lock contention has a serialising affect on the flushes anyway. >> >> >> -- >> Alex Bennée -- Alex Bennée