On 07/03/2022 00:42, bhe@xxxxxxxxxx wrote: > [...] >> Let me know your thoughts Petr / Baoquan - it would add slightly more >> code / complexity, but in my opinion the payback is very good. >> Cheers, > > The ideal situation is each panic notifier has an order or index to > indicate its priority. Wondering how to make it. What I think of is > copying initcall. We have several priorities, at the same priority, > execution sequence is not important. Not sure if I get your point. > > ~~~~~~~ > #define core_initcall(fn) __define_initcall(fn, 1) > #define core_initcall_sync(fn) __define_initcall(fn, 1s) > ...... > #define late_initcall(fn) __define_initcall(fn, 7) > #define late_initcall_sync(fn) __define_initcall(fn, 7s) > Hi Baoquan, thanks for you consideration! In fact, the notifiers infrastructure already have a mechanism of ordering, my idea is to make use of that. It's not that different from the initcall system... For instance, the code in the notifier register function checks for the priority field in the notifier block: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/kernel/notifier.c#n31 . For example, the Xen panic notifier is one of the few blocks that make use of that, currently: static struct notifier_block xen_panic_block = { .notifier_call = xen_panic_event, .priority = INT_MIN }; (see https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/arch/x86/xen/enlighten.c#n286) In this case, xen_panic_event() will be the latest one to run. My idea is to make use of that in *all* panic notifiers, having a table/list on panic_notifier.h (defines or enum, I'll think about that when writing this part) so all notifiers are documented and the ordering is clear and enforced. Makes sense to you? Cheers, Guilherme
