On Sat, May 16, 2020 at 06:11:20AM +0800, kbuild test robot wrote: > tree: https://git.kernel.org/pub/scm/linux/kernel/git/peterz/queue.git sched/core > head: 073d35d51f30267ccb43479be42d382f9b03fd9a > commit: df24fd8a5838c3e24dc7a41b37c5812cce80dd43 [4/9] x86, sched: Prevent divisions by zero in frequency invariant accounting > config: i386-randconfig-a011-20200515 (attached as .config) > compiler: gcc-4.9 (Ubuntu 4.9.3-13ubuntu2) 4.9.3 > reproduce: > git checkout df24fd8a5838c3e24dc7a41b37c5812cce80dd43 > # save the attached .config to linux build tree > make ARCH=i386 > > If you fix the issue, kindly add following tag as appropriate > Reported-by: kbuild test robot <lkp(a)intel.com&gt; > > All errors (new ones prefixed by >>, old ones prefixed by <<): > > ld: arch/x86/kernel/smpboot.o: in function `arch_scale_freq_tick': > > > arch/x86/kernel/smpboot.c:2083: undefined reference to `__udivdi3' > > vim +2083 arch/x86/kernel/smpboot.c > > 2061 > 2062 void arch_scale_freq_tick(void) > 2063 { > 2064 u64 freq_scale = SCHED_CAPACITY_SCALE; > 2065 u64 aperf, mperf; > 2066 u64 acnt, mcnt; > 2067 > 2068 if (!arch_scale_freq_invariant()) > 2069 return; > 2070 > 2071 rdmsrl(MSR_IA32_APERF, aperf); > 2072 rdmsrl(MSR_IA32_MPERF, mperf); > 2073 > 2074 acnt = aperf - this_cpu_read(arch_prev_aperf); > 2075 mcnt = mperf - this_cpu_read(arch_prev_mperf); > 2076 > 2077 this_cpu_write(arch_prev_aperf, aperf); > 2078 this_cpu_write(arch_prev_mperf, mperf); > 2079 > 2080 if (check_shl_overflow(acnt, 2*SCHED_CAPACITY_SHIFT, &acnt)) > 2081 goto error; > 2082 > > 2083 if (check_mul_overflow(mcnt, arch_max_freq_ratio, &mcnt) || !mcnt) *sigh*,.. I hate computers. I'll try and have a look later, but if if you have a nice solution Giovanni, don't hessitate to tell me ;-)

On Mon, May 18, 2020 at 12:56:18PM +0200, Giovanni Gherdovich wrote: > On Mon, 2020-05-18 at 11:35 +0200, Peter Zijlstra wrote: > > On Sat, May 16, 2020 at 06:11:20AM +0800, kbuild test robot wrote: > > > tree: https://git.kernel.org/pub/scm/linux/kernel/git/peterz/queue.git sched/core > > > head: 073d35d51f30267ccb43479be42d382f9b03fd9a > > > commit: df24fd8a5838c3e24dc7a41b37c5812cce80dd43 [4/9] x86, sched: Prevent divisions by zero in frequency invariant accounting > > > config: i386-randconfig-a011-20200515 (attached as .config) > > > compiler: gcc-4.9 (Ubuntu 4.9.3-13ubuntu2) 4.9.3 > > > reproduce: > > > git checkout df24fd8a5838c3e24dc7a41b37c5812cce80dd43 > > > # save the attached .config to linux build tree > > > make ARCH=i386 > > > > > > If you fix the issue, kindly add following tag as appropriate > > > Reported-by: kbuild test robot <lkp(a)intel.com&gt; > > > > > > All errors (new ones prefixed by >>, old ones prefixed by <<): > > > > > > ld: arch/x86/kernel/smpboot.o: in function `arch_scale_freq_tick': > > > > > arch/x86/kernel/smpboot.c:2083: undefined reference to `__udivdi3' > > > > > > vim +2083 arch/x86/kernel/smpboot.c > > > > > > 2061 > > > 2062 void arch_scale_freq_tick(void) > > > 2063 { > > > 2064 u64 freq_scale = SCHED_CAPACITY_SCALE; > > > 2065 u64 aperf, mperf; > > > 2066 u64 acnt, mcnt; > > > 2067 > > > 2068 if (!arch_scale_freq_invariant()) > > > 2069 return; > > > 2070 > > > 2071 rdmsrl(MSR_IA32_APERF, aperf); > > > 2072 rdmsrl(MSR_IA32_MPERF, mperf); > > > 2073 > > > 2074 acnt = aperf - this_cpu_read(arch_prev_aperf); > > > 2075 mcnt = mperf - this_cpu_read(arch_prev_mperf); > > > 2076 > > > 2077 this_cpu_write(arch_prev_aperf, aperf); > > > 2078 this_cpu_write(arch_prev_mperf, mperf); > > > 2079 > > > 2080 if (check_shl_overflow(acnt, 2*SCHED_CAPACITY_SHIFT, &acnt)) > > > 2081 goto error; > > > 2082 > > > > 2083 if (check_mul_overflow(mcnt, arch_max_freq_ratio, &mcnt) || !mcnt) > > > > *sigh*,.. I hate computers. I'll try and have a look later, but if if > > you have a nice solution Giovanni, don't hessitate to tell me ;-) > > Hello Peter, > > today I'm speaking at OSPM but tomorrow I'll see how to fix this. Ha!, yes, I'll be there, listening.. :-) So far the easiest fix I've come up with is simply limiting all this to 64bit.. like who cares about 32bit anyway :-))))