On Fri, 25 Aug 2017, Thomas Gleixner wrote: CC + Rostedt
> On Fri, 25 Aug 2017, kbuild test robot wrote: > > > Hi Thomas, > > > > It's probably a bug fix that unveils the link errors. > > > > tree: https://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git > > WIP.x86/apic > > head: 395b2c62edea5a2bb8a8786392feb12fae5917a7 > > commit: 902f1bb88397dd6769c98b2177bbda134b3a1ef2 [40/43] x86/idt: Deinline > > setup functions > > config: i386-randconfig-s0-201734 (attached as .config) > > compiler: gcc-6 (Debian 6.2.0-3) 6.2.0 20160901 > > reproduce: > > git checkout 902f1bb88397dd6769c98b2177bbda134b3a1ef2 > > # save the attached .config to linux build tree > > make ARCH=i386 > > > > All errors (new ones prefixed by >>): > > > > >> arch/x86/kernel/irq.o:(__tracepoints+0x170): undefined reference to > > >> `trace_resched_ipi_reg' > > >> arch/x86/kernel/irq.o:(__tracepoints+0x174): undefined reference to > > >> `trace_resched_ipi_unreg' > > arch/x86/kernel/irq.o:(__tracepoints+0x184): undefined reference to > > `trace_resched_ipi_reg' > > arch/x86/kernel/irq.o:(__tracepoints+0x188): undefined reference to > > `trace_resched_ipi_unreg' > > > > That link error is caused by the tracepoint code being stupid enough to > generate tracepoint stuff in an object file whether they are used or not. > > The issue here is that the reschedule ipi tracepoint has an initializer > function which is only compiled in when CONFIG_SMP=y. > > That tracepoint is not used in irq.o at all, but still the tracepoint macro > hell generates something for it: > > objdump -t ../build-386/arch/x86/kernel/irq.o | grep resched > 00000048 l O _ftrace_events 00000004 __event_reschedule_exit > 00000a00 l O .data 0000004c event_reschedule_exit > 0000004c l O _ftrace_events 00000004 __event_reschedule_entry > 00000a60 l O .data 0000004c event_reschedule_entry > 00000048 l O __tracepoints_ptrs 00000004 > __tracepoint_ptr_reschedule_exit > 00000188 l O __tracepoints_strings 00000010 > __tpstrtab_reschedule_exit > 0000004c l O __tracepoints_ptrs 00000004 > __tracepoint_ptr_reschedule_entry > 00000198 l O __tracepoints_strings 00000011 > __tpstrtab_reschedule_entry > 0000017c g O __tracepoints 00000014 __tracepoint_reschedule_entry > 00000000 *UND* 00000000 trace_resched_ipi_reg > 00000168 g O __tracepoints 00000014 __tracepoint_reschedule_exit > 00000000 *UND* 00000000 trace_resched_ipi_unreg > > Brilliant stuff that. I'll hide the tracepoint behind a CONFIG_SMP ifdef > for now. > > Thanks, > > tglx >
