On 28/10/25 17:25, Frederic Weisbecker wrote: > +Cc Phil Auld > > Le Fri, Oct 10, 2025 at 05:38:10PM +0200, Valentin Schneider a écrit : >> Patches >> ======= >> >> o Patches 1-2 are standalone objtool cleanups. > > Would be nice to get these merged. > >> o Patches 3-4 add an RCU testing feature. > > I'm taking this one. >
Thanks! >> >> o Patches 5-6 add infrastructure for annotating static keys and static calls >> that may be used in noinstr code (courtesy of Josh). >> o Patches 7-20 use said annotations on relevant keys / calls. >> o Patch 21 enforces proper usage of said annotations (courtesy of Josh). >> >> o Patch 22 deals with detecting NOINSTR text in modules > > Not sure how to route those. If we wait for each individual subsystem, > this may take a while. > At least the __ro_after_init ones could go as their own thing since they're standalone, but yeah they're the ones touching all sorts of subsystems :/ >> o Patches 23-24 deal with kernel text sync IPIs > > I would be fine taking those (the concerns I had are just details) > but they depend on all the annotations. Alternatively I can take the whole > thing but then we'll need some acks. > >> o Patches 25-29 deal with kernel range TLB flush IPIs > > I'll leave these more time for now ;o) > And if they ever go somewhere, it should be through x86 tree. > > Also, here is another candidate usecase for this deferral thing. > I remember Phil Auld complaining that stop_machine() on CPU offlining was > a big problem for nohz_full. Especially while we are working on > a cpuset interface to toggle nohz_full but this will require the CPUs > to be offline. > Yeah that does ring a bell... > So my point is that when a CPU goes offline, stop_machine() puts all > CPUs into a loop with IRQs disabled. CPUs in userspace could possibly > escape that since they don't touch the kernel anyway. But as soon as > they enter the kernel, they should either acquire the final state of > stop_machine if completed or join the global loop if in the middle. > I need to have a think about that one; one pain point I see is the context tracking work has to be NMI safe since e.g. an NMI can take us out of userspace. Another is that NOHZ-full CPUs need to be special cased in the stop machine queueing / completion. /me goes fetch a new notebook > Thanks. > > -- > Frederic Weisbecker > SUSE Labs
