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[189.47.87.73]) by smtp.gmail.com with ESMTPSA id f203sm4830714qke.100.2020.03.16.07.01.35 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 16 Mar 2020 07:01:37 -0700 (PDT) Subject: Re: [PATCH] kernel/hung_task.c: Introduce sysctl to print all traces when a hung task is detected To: Tetsuo Handa , Kees Cook Cc: linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-doc@vger.kernel.org, mcgrof@kernel.org, yzaikin@google.com, tglx@linutronix.de, kernel@gpiccoli.net References: <20200310155650.17968-1-gpiccoli@canonical.com> <202003132011.8143A71FE@keescook> From: "Guilherme G. Piccoli" Openpgp: preference=signencrypt Autocrypt: addr=gpiccoli@canonical.com; prefer-encrypt=mutual; keydata= mQENBFpVBxcBCADPNKmu2iNKLepiv8+Ssx7+fVR8lrL7cvakMNFPXsXk+f0Bgq9NazNKWJIn Qxpa1iEWTZcLS8ikjatHMECJJqWlt2YcjU5MGbH1mZh+bT3RxrJRhxONz5e5YILyNp7jX+Vh 30rhj3J0vdrlIhPS8/bAt5tvTb3ceWEic9mWZMsosPavsKVcLIO6iZFlzXVu2WJ9cov8eQM/ irIgzvmFEcRyiQ4K+XUhuA0ccGwgvoJv4/GWVPJFHfMX9+dat0Ev8HQEbN/mko/bUS4Wprdv 7HR5tP9efSLucnsVzay0O6niZ61e5c97oUa9bdqHyApkCnGgKCpg7OZqLMM9Y3EcdMIJABEB AAG0LUd1aWxoZXJtZSBHLiBQaWNjb2xpIDxncGljY29saUBjYW5vbmljYWwuY29tPokBNwQT AQgAIQUCWmClvQIbAwULCQgHAgYVCAkKCwIEFgIDAQIeAQIXgAAKCRDOR5EF9K/7Gza3B/9d 5yczvEwvlh6ksYq+juyuElLvNwMFuyMPsvMfP38UslU8S3lf+ETukN1S8XVdeq9yscwtsRW/ 4YoUwHinJGRovqy8gFlm3SAtjfdqysgJqUJwBmOtcsHkmvFXJmPPGVoH9rMCUr9s6VDPox8f q2W5M7XE9YpsfchS/0fMn+DenhQpV3W6pbLtuDvH/81GKrhxO8whSEkByZbbc+mqRhUSTdN3 iMpRL0sULKPVYbVMbQEAnfJJ1LDkPqlTikAgt3peP7AaSpGs1e3pFzSEEW1VD2jIUmmDku0D LmTHRl4t9KpbU/H2/OPZkrm7809QovJGRAxjLLPcYOAP7DUeltveuQENBFpVBxcBCADbxD6J aNw/KgiSsbx5Sv8nNqO1ObTjhDR1wJw+02Bar9DGuFvx5/qs3ArSZkl8qX0X9Vhptk8rYnkn pfcrtPBYLoux8zmrGPA5vRgK2ItvSc0WN31YR/6nqnMfeC4CumFa/yLl26uzHJa5RYYQ47jg kZPehpc7IqEQ5IKy6cCKjgAkuvM1rDP1kWQ9noVhTUFr2SYVTT/WBHqUWorjhu57/OREo+Tl nxI1KrnmW0DbF52tYoHLt85dK10HQrV35OEFXuz0QPSNrYJT0CZHpUprkUxrupDgkM+2F5LI bIcaIQ4uDMWRyHpDbczQtmTke0x41AeIND3GUc+PQ4hWGp9XABEBAAGJAR8EGAEIAAkFAlpV BxcCGwwACgkQzkeRBfSv+xv1wwgAj39/45O3eHN5pK0XMyiRF4ihH9p1+8JVfBoSQw7AJ6oU 1Hoa+sZnlag/l2GTjC8dfEGNoZd3aRxqfkTrpu2TcfT6jIAsxGjnu+fUCoRNZzmjvRziw3T8 egSPz+GbNXrTXB8g/nc9mqHPPprOiVHDSK8aGoBqkQAPZDjUtRwVx112wtaQwArT2+bDbb/Y Yh6gTrYoRYHo6FuQl5YsHop/fmTahpTx11IMjuh6IJQ+lvdpdfYJ6hmAZ9kiVszDF6pGFVkY kHWtnE2Aa5qkxnA2HoFpqFifNWn5TyvJFpyqwVhVI8XYtXyVHub/WbXLWQwSJA4OHmqU8gDl X18zwLgdiQ== Message-ID: <627a34c6-6ccd-d6c9-ae91-fd7cb4087e96@canonical.com> Date: Mon, 16 Mar 2020 11:01:34 -0300 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.9.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 14/03/2020 01:27, Tetsuo Handa wrote: > On 2020/03/14 12:12, Kees Cook wrote: >> On Fri, Mar 13, 2020 at 02:23:37PM -0300, Guilherme G. Piccoli wrote: >>> Kees / Testsuo, are you OK with this patch once I resend with the >>> suggestions you gave me? >> >> I think so, yes. Send a v2 (to akpm with us in CC). >> >>> Is there anybody else I should loop in the patch that should take a >>> look? Never sent sysctl stuff before, sorry if I forgot somebody heheh >> >> akpm usually takes these kinds of things. >> > > Well, maybe sysctl_hung_task_all_cpu_backtrace = 1 by default is better for > compatibility? Please CC or BCC kernel-testing people so that they can add > hung_task_all_cpu_backtrace=1 kernel command line parameter to their testing > environments if sysctl_hung_task_all_cpu_backtrace = 0 by default. > Thanks a lot Kees and Tetsuo, I'll implement the suggestions and loop the kernel-testing and akpm in V2. About being default, I personally think it's better / more reasonable to have this parameter defaults to 0, to keep consistency with all other *_all_cpu_backtrace parameters. Right now kernel shows the backtraces only when hung_task_panic is set, so the idea of this patch is to decouple the toggles and allow the user to decide about this policy. Nevertheless, if people consider that would be good to have it as enabled by default, I can change it in a potential V3. Cheers, Guilherme