On Tue, Sep 01, 2020 at 03:03:28PM +0800, Rong Chen wrote:
>
>
> 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 <l...@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
Thank you! May I add your Tested-by?
Thanx, Paul
> Best Regards,
> Rong Chen
>
> >
> > Thanx, Paul
> >
> > ------------------------------------------------------------------------
> >
> > commit d301e320e952e2e604d83d9540e52510b0eb3d94
> > Author: Paul E. McKenney <paul...@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 <l...@intel.com>
> > Signed-off-by: Paul E. McKenney <paul...@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 -- l...@lists.01.org
> > To unsubscribe send an email to lkp-le...@lists.01.org
>
