Messages in this thread Patch in this message | | | Subject | Re: [LKP] Re: [rcuperf] 4e88ec4a9e: UBSAN:division-overflow_in_arch/x86/include/asm/div64.h | From | Rong Chen <> | Date | Tue, 1 Sep 2020 15:03:28 +0800 |
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On 8/31/20 11:50 PM, Paul E. McKenney wrote: > On Mon, Aug 31, 2020 at 08:01:22PM +0800, kernel test robot wrote: >> Greeting, >> >> FYI, we noticed the following commit (built with gcc-9): >> >> commit: 4e88ec4a9eb17527e640b063f79e5b875733eb53 ("rcuperf: Change rcuperf to rcuscale") >> https://git.kernel.org/cgit/linux/kernel/git/next/linux-next.git master >> >> >> in testcase: trinity >> with following parameters: >> >> runtime: 300s >> >> test-description: Trinity is a linux system call fuzz tester. >> test-url: http://codemonkey.org.uk/projects/trinity/ >> >> >> on test machine: qemu-system-i386 -enable-kvm -cpu SandyBridge -smp 2 -m 8G >> >> caused below changes (please refer to attached dmesg/kmsg for entire log/backtrace): >> >> >> +---------------------------------------------------------+------------+------------+ >> | | 65bd77f554 | 4e88ec4a9e | >> +---------------------------------------------------------+------------+------------+ >> | boot_successes | 13 | 0 | >> | boot_failures | 0 | 14 | >> | UBSAN:division-overflow_in_arch/x86/include/asm/div64.h | 0 | 14 | >> | error:#[##] | 0 | 14 | >> | EIP:main_func.cold | 0 | 14 | >> | Kernel_panic-not_syncing:Fatal_exception | 0 | 14 | >> +---------------------------------------------------------+------------+------------+ >> >> >> If you fix the issue, kindly add following tag >> Reported-by: kernel test robot <lkp@intel.com> > Does the patch below fix this for you?
Yes, this patch can fix the issue, and nreaders was adjusted to 1:
[ 5.953645] The force parameter has not been set to 1. The Iris poweroff handler will not be installed. [ 12.546587] rcu-ref-scale: --- Start of test: verbose=0 shutdown=1 holdoff=10 loops=10000 nreaders=-1 nruns=30 readdelay=0 [ 12.561495] ------------[ cut here ]------------ [ 12.562016] ref_scale_init: nreaders = 0, adjusted to 1 [ 12.562601] WARNING: CPU: 0 PID: 1 at kernel/rcu/refscale.c:684 ref_scale_init+0x653/0x80
Best Regards, Rong Chen
> > Thanx, Paul > > ------------------------------------------------------------------------ > > commit d301e320e952e2e604d83d9540e52510b0eb3d94 > Author: Paul E. McKenney <paulmck@kernel.org> > Date: Thu Aug 27 09:58:19 2020 -0700 > > refscale: Bounds-check module parameters > > The default value for refscale.nreaders is -1, which results in the code > setting the value to three-quarters of the number of CPUs. On single-CPU > systems, this results in three-quarters of the value one, which the C > language's integer arithmetic rounds to zero. This in turn results in > a divide-by-zero error. > > This commit therefore adds bounds checking to the refscale module > parameters, so that if they are less than one, they are set to the > value one. > > Reported-by: kernel test robot <lkp@intel.com> > Signed-off-by: Paul E. McKenney <paulmck@kernel.org> > > diff --git a/kernel/rcu/refscale.c b/kernel/rcu/refscale.c > index 952595c..fb5f20d 100644 > --- a/kernel/rcu/refscale.c > +++ b/kernel/rcu/refscale.c > @@ -681,6 +681,12 @@ ref_scale_init(void) > // Reader tasks (default to ~75% of online CPUs). > if (nreaders < 0) > nreaders = (num_online_cpus() >> 1) + (num_online_cpus() >> 2); > + if (WARN_ONCE(loops <= 0, "%s: loops = %ld, adjusted to 1\n", __func__, loops)) > + loops = 1; > + if (WARN_ONCE(nreaders <= 0, "%s: nreaders = %d, adjusted to 1\n", __func__, nreaders)) > + nreaders = 1; > + if (WARN_ONCE(nruns <= 0, "%s: nruns = %d, adjusted to 1\n", __func__, nruns)) > + nruns = 1; > reader_tasks = kcalloc(nreaders, sizeof(reader_tasks[0]), > GFP_KERNEL); > if (!reader_tasks) { > _______________________________________________ > LKP mailing list -- lkp@lists.01.org > To unsubscribe send an email to lkp-leave@lists.01.org
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