On 19/07/2022 17:33, Arjan van de Ven wrote: > On 7/19/2022 12:53 PM, Guilherme G. Piccoli wrote: >> Currently we have a debug infrastructure in the notifiers file, but >> it's very simple/limited. Extend it by: >> >> (a) Showing all registered/unregistered notifiers' callback names; > > > I'm not yet convinced that this is the right direction. > The original intent for this "debug" feature was to be lightweight enough > that it could run in production, since at the time, rootkits > liked to clobber/hijack notifiers and there were also some other signs of > corruption at the time. > > By making something print (even at pr_info) for what are probably frequent > non-error operations, you turn something that is light > into something that's a lot more heavy and generally that's not a great > idea... it'll be a performance surprise. > >
Is registering/un-registering notifiers a hot path, or performance sensitive usually? For me, this patch proved to be very useful, and once enabled, shows relatively few entries in dmesg, these operations aren't so common thing it seems. Also, if this Kconfig option was meant to run in production, maybe the first thing would be have some sysfs tuning or anything able to turn it on - I've worked with a variety of customers and the most terrifying thing in servers is to install a new kernel and reboot heh My understanding is that this debug infrastructure would be useful for notifiers writers and people playing with the core notifiers code...tracing would be much more useful in the context of checking if some specific notifier got registered/executed in production environment I guess. Cheers, Guilherme _______________________________________________ kexec mailing list kexec@lists.infradead.org http://lists.infradead.org/mailman/listinfo/kexec
