From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:50074) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1aK6Fz-00026d-AZ for qemu-devel@nongnu.org; Fri, 15 Jan 2016 10:25:44 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1aK6Fu-0001In-VQ for qemu-devel@nongnu.org; Fri, 15 Jan 2016 10:25:42 -0500 Received: from mail-wm0-x22f.google.com ([2a00:1450:400c:c09::22f]:35557) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1aK6Fu-0001Id-Ok for qemu-devel@nongnu.org; Fri, 15 Jan 2016 10:25:38 -0500 Received: by mail-wm0-x22f.google.com with SMTP id f206so24674234wmf.0 for ; Fri, 15 Jan 2016 07:25:38 -0800 (PST) References: <87oacqd7v9.fsf@linaro.org> <87bn8nc5kb.fsf@linaro.org> <878u3qdhfw.fsf@linaro.org> From: Alex =?utf-8?Q?Benn=C3=A9e?= In-reply-to: Date: Fri, 15 Jan 2016 15:25:35 +0000 Message-ID: <877fjadfv4.fsf@linaro.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit Subject: Re: [Qemu-devel] Status of my hacks on the MTTCG WIP branch List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: alvise rigo Cc: MTTCG Devel , Paolo Bonzini , Pranith Kumar , QEMU Developers , KONRAD Frederic alvise rigo writes: > On Fri, Jan 15, 2016 at 3:51 PM, Alex Bennée wrote: >> >> alvise rigo writes: >> >>> This problem could be related to a missing multi-threaded aware >>> translation of the atomic instructions. >>> I'm working on this missing piece, probably the next week I will >>> publish something. >> >> Maybe. We still have Fred's: >> >> Use atomic cmpxchg to atomically check the exclusive value in a STREX >> >> Which I think papers over the cracks for both arm and aarch64 in MTTCG >> while not being as correct as your work. > > Keep in mind that Linux on arm64 uses the LDXP/STXP instructions that > exist solely in aarch64. > These instructions are purely emulated now and can potentially write > 128 bits of data in a non-atomic fashion. Sure, but I doubt they are the reason for this hang as the kernel doesn't use them. > > Regards, > alvise > >> >>> >>> Regards, >>> alvise >>> >>> On Fri, Jan 15, 2016 at 3:24 PM, Pranith Kumar wrote: >>>> Hi Alex, >>>> >>>> On Fri, Jan 15, 2016 at 8:53 AM, Alex Bennée wrote: >>>>> Can you try this branch: >>>>> >>>>> >>>>> https://github.com/stsquad/qemu/tree/mttcg/multi_tcg_v8_wip_ajb_fix_locks-r1 >>>>> >>>>> I think I've caught all the things likely to screw up addressing. >>>>> >>>> >>>> I tried this branch and the boot hangs like follows: >>>> >>>> [ 2.001083] random: systemd-udevd urandom read with 1 bits of entropy >>>> available >>>> main-loop: WARNING: I/O thread spun for 1000 iterations >>>> [ 23.778970] INFO: rcu_sched detected stalls on CPUs/tasks: {} (detected >>>> by 0, t=2102 jiffies, g=-165, c=-166, q=83) >> >> This is just saying the kernel has been waiting for a while and nothing >> has happened. >> >>>> I will try to debug and see where it is hanging. >> >> If we knew what the kernel was waiting for that would be useful to know. >> >>>> >>>> Thanks! >>>> -- >>>> Pranith >> >> >> -- >> Alex Bennée -- Alex Bennée