Hi, On Thu, 16 Jan 2025, Petr Mladek wrote: > On Thu 2025-01-16 08:10:44, Joe Lawrence wrote: > > 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 > > Good to know. I havn't seen this yet. > > > >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? > > It looks like. The caller ID information is available also via > /dev/kmsg but the older dmesg version did not show it. I guess that > they just added support to parse and show it. It actually makes > sense to show the same output independently on whether the messages > are read via syslog or /dev/kmsg. > > So, we need this patch, definitely ;-) Yes. Madhavan, could you add the above findings to the commit log when you submit a new version, please? Thank you, Miroslav
