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[24.9.64.241]) by smtp.gmail.com with ESMTPSA id o7sm3502364iop.51.2021.01.07.10.13.55 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 07 Jan 2021 10:13:56 -0800 (PST) Subject: Re: [PATCH] kunit: tool: Force the use of the 'tty' console for UML To: Petr Mladek , David Gow Cc: Andy Shevchenko , Brendan Higgins , Senozhatsky , Sergey Senozhatsky , "open list:KERNEL SELFTEST FRAMEWORK" , KUnit Development , Linux Kernel Mailing List , Shuah Khan References: <20201222073900.3490607-1-davidgow@google.com> <20201222111102.GC4077@smile.fi.intel.com> <4ae7779c-15c5-0474-5840-44531dcf1d94@linuxfoundation.org> <3828c7ee-52b0-42f9-5771-74ef9386756c@linuxfoundation.org> <20210105185731.GT4077@smile.fi.intel.com> <918b2d05-f51b-0866-89b3-19a016abdaa3@linuxfoundation.org> From: Shuah Khan Message-ID: <578de82c-5119-78e4-4497-c8a8d642388d@linuxfoundation.org> Date: Thu, 7 Jan 2021 11:13:54 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.5.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 1/7/21 9:53 AM, Petr Mladek wrote: > On Wed 2021-01-06 12:29:12, David Gow wrote: >> On Wed, Jan 6, 2021 at 3:52 AM Shuah Khan wrote: >>> >>> On 1/5/21 11:57 AM, Andy Shevchenko wrote: >>>> On Tue, Jan 05, 2021 at 09:34:33AM -0700, Shuah Khan wrote: >>>>> On 1/5/21 9:21 AM, Petr Mladek wrote: >>>>>> On Mon 2021-01-04 09:23:57, Shuah Khan wrote: >>>>>>> On 12/22/20 4:11 AM, Andy Shevchenko wrote: >>>>>>>> On Mon, Dec 21, 2020 at 11:39:00PM -0800, David Gow wrote: >>>>>>>>> kunit_tool relies on the UML console outputting printk() output to the >>>>>>>>> tty in order to get results. Since the default console driver could >>>>>>>>> change, pass 'console=tty' to the kernel. >>>>>>>>> >>>>>>>>> This is triggered by a change[1] to use ttynull as a fallback console >>>>>>>>> driver which -- by chance or by design -- seems to have changed the >>>>>>>>> default console output on UML, breaking kunit_tool. While this may be >>>>>>>>> fixed, we should be less fragile to such changes in the default. >>>>>>>>> >>>>>>>>> [1]: >>>>>>>>> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=757055ae8dedf5333af17b3b5b4b70ba9bc9da4e >>>>>>>> >>>>>>>> Reported-by: Andy Shevchenko >>>>>>>> Tested-by: Andy Shevchenko >>>>>>>> >>>>>>> >>>>>>> Thank you all. Now in linux-kselftest kunit-fixes branch. >>>>>>> >>>>>>> Will send this up for rc3. >>>>>>> >>>>>>> Sorry for the delay - have been away from the keyboard for a >>>>>>> bit. >>>>>> >>>>>> JFYI, I am not sure that this is the right solution. I am >>>>>> looking into it, see >>>>>> https://lore.kernel.org/linux-kselftest/X%2FSRA1P8t+ONZFKb@alley/ >>>>>> for more details. >>>>>> >>>>> >>>>> Thanks Petr. I will hold off on sending the patch up to Linus and >>>>> let you find a the right solution. >>>> >>>> Please. leave it in Linux Next at least. Otherwise kunit will be broken for a >>>> long time which is not good. >>>> >>>> >>> >>> Yes. That is the plan. It will be in there until real fix comes in. > > The real fix would be too complicated for 5.11-rc3. Instead, I > proposed to revert the problematic commit, see > https://lore.kernel.org/lkml/20210107164400.17904-2-pmladek@suse.com/ > I would like to push it for 5.11-rc3. > >> Personally, I think that this patch makes some sense to keep even if >> the underlying issue with ttynull is resolved. Given that kunit.py >> requires the console output, explicitly stating we want console=tty >> set is probably worth doing rather than relying on it being the >> default. > > I agree that the patch makes sense on its own. kunit depends on the > particular console. Note that "tty" is actually the UML-specific > stdio console implemented in arch/um/drivers/stdio_console.c. > The proposal sounds like revert the problem commit https://lore.kernel.org/lkml/20210107164400.17904-2-pmladek@suse.com/ and also send kunit fix up. Sounds reasonable to me. I will send it for 5.11-rc3 thanks, -- Shuah