linux-kernel - Re: [tip:WIP.x86/apic 40/43] arch/x86/kernel/irq.o:(__tracepoints+0x170): undefined reference to `trace_resched_ipi

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Message-ID: <alpine.DEB.2.20.1708251426050.1883@nanos>
Date:   Fri, 25 Aug 2017 14:26:18 +0200 (CEST)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     kbuild test robot <fengguang.wu@...el.com>
cc:     kbuild-all@...org, LKML <linux-kernel@...r.kernel.org>,
        tipbuild@...or.com, Steven Rostedt <rostedt@...dmis.org>
Subject: Re: [tip:WIP.x86/apic 40/43] arch/x86/kernel/irq.o:(__tracepoints+0x170):
 undefined reference to `trace_resched_ipi_reg'

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
>