On Fri, May 21, 2021 at 12:05:27AM +0200, J Mårtensson wrote: > Hi, > I have been trying to add a new scheduler to the Linux kernel. I have > found that to add a sched_class, I need to add it to SCHED_DATA in > vmlinux.lds.h. instead of editing the now removed .next variable. I'm assuming that you are referring to this patch from Steven Rostedt, right? https://lore.kernel.org/lkml/20191219214451.340746474@xxxxxxxxxxx/ > Depending on what order I put into the priority list, it will crash > the kernel during the booting process after rebooting. Any tips on > what could be causing this would be appreciated! I am not sure if I that would help, but if I were you I would try to isolate the problem with available debugging mechanisms available in the kernel. Have you tried compiling the kernel with CONFIG_SCHED_DEBUG=y and make use of Early Print K ? https://www.kernel.org/doc/html/latest/x86/earlyprintk.html Since it's rebooting due to the error, you won't be able the see the logs... so if you enable early printk and get those messages across a piece of hardware that's not rebooting then at least you will be able to read those messages and add/rem statements to help you figure out what's going wrong. there is no silver-bullet solution for that, but I'm sure that you will have a lot of fun trying to debug this. Once you find the solution, please share with us. I'm sure this will be benefitial for future developers with similar questions. > > Currently this works > > #define SCHED_DATA \ > STRUCT_ALIGN(); \ > __begin_sched_classes = .; \ > *(__idle_sched_class) \ > *(__my_sched_class) \ > *(__fair_sched_class) \ > *(__rt_sched_class) \ > *(__dl_sched_class) \ > *(__stop_sched_class) \ > __end_sched_classes = .; > This most likely works because during the OS booting, all processes executed have their scheduling needs sorted out from the dl_sched_class to the fair_sched_class. So either there is no moment when the CPU is idle throughout the process (unlikely) or the bug on your _my_sched_class isn't triggered when there is nothing in the CPU run queue. I can be wrong though, so if anyone has a better explanation, please chime in. > While this does not > > #define SCHED_DATA \ > STRUCT_ALIGN(); \ > __begin_sched_classes = .; \ > *(__idle_sched_class) \ > *(__fair_sched_class) \ > *(__my_sched_class) \ > *(__rt_sched_class) \ > *(__dl_sched_class) \ > *(__stop_sched_class) \ > __end_sched_classes = .; > It's hard to speculate about the reason why it's failing but if I was a gambling man I would say that *given the fact* that __my_sched_class has a higher-priority than the __fair_sched_class, it breaks when trying to execute the __my_sched_class methods defined in the DEFINE_SCHED_CLASS macro. Example from the fair.c sched class: https://github.com/torvalds/linux/blob/02dbb7246c5bbbbe1607ebdc546ba5c454a664b1/kernel/sched/fair.c#L11261-L11304 Paulo Miguel Almeida > > Regards > Jacob > > _______________________________________________ > Kernelnewbies mailing list > Kernelnewbies@xxxxxxxxxxxxxxxxx > https://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies _______________________________________________ Kernelnewbies mailing list Kernelnewbies@xxxxxxxxxxxxxxxxx https://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
