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[68.160.135.240]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-72d40658c4bsm11140160b3a.100.2025.01.16.05.10.46 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 16 Jan 2025 05:10:48 -0800 (PST) Message-ID: Date: Thu, 16 Jan 2025 08:10:44 -0500 Precedence: bulk X-Mailing-List: linux-kselftest@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.15.1 Content-Language: en-US To: Petr Mladek , Madhavan Srinivasan Cc: jikos@kernel.org, mbenes@suse.cz, shuah@kernel.org, mpe@ellerman.id.au, npiggin@gmail.com, christophe.leroy@csgroup.eu, naveen@kernel.org, live-patching@vger.kernel.org, linux-kselftest@vger.kernel.org, linuxppc-dev@lists.ozlabs.org References: <20250114143144.164250-1-maddy@linux.ibm.com> From: Joe Lawrence Subject: Re: [PATCH] selftests: livepatch: handle PRINTK_CALLER in check_result() In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 1/16/25 04:29, Petr Mladek wrote: > On Tue 2025-01-14 20:01:44, Madhavan Srinivasan wrote: >> Some arch configs (like ppc64) enable CONFIG_PRINTK_CALLER, which >> adds the caller id as part of the dmesg. Due to this, even though >> the expected vs observed are same, end testcase results are failed. > > CONFIG_PRINTK_CALLER is not the only culprit. We (SUSE) have it enabled > as well and the selftests pass without this patch. > > The difference might be in dmesg. It shows the caller only when > the messages are read via the syslog syscall (-S) option. It should > not show the caller when the messages are read via /dev/kmsg > which should be the default. > > I wonder if you define an alias to dmesg which adds the "-S" option > or if /dev/kmsg is not usable from some reason. > Hi Petr, To see the thread markers on a RHEL-9.6 machine, I built and installed the latest dmesg from: https://github.com/util-linux/util-linux and ran Madhavan's tests. I don't think there was any alias involved: $ alias | grep dmesg (nothing) $ ~/util-linux/dmesg | tail -n1 [ 4361.322790] [ T98877] % rmmod test_klp_livepatch >From util-linux's 467a5b3192f1 ("dmesg: add caller_id support"): The dmesg -S using the old syslog interface supports printing the PRINTK_CALLER field but currently standard dmesg does not support printing the field if present. There are utilities that use dmesg and so it would be optimal if dmesg supported PRINTK_CALLER as well. does that imply that printing the thread IDs is now a (util-linux's) dmesg default? Regards, -- Joe