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Date:   Fri, 26 May 2023 15:59:48 +0800
From:   Yujie Liu <yujie.liu@intel.com>
To:     "Paul E. McKenney" <paulmck@kernel.org>
CC:     <oe-lkp@lists.linux.dev>, <lkp@intel.com>,
        <linux-kernel@vger.kernel.org>, <rcu@vger.kernel.org>
Subject: Re: [paulmck-rcu:dev.2023.05.20a] [rcuscale] 812195e4f7:
 BUG:kernel_NULL_pointer_dereference,address
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References: <202305241757.57c30887-yujie.liu@intel.com>
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Hi Paul,

On Thu, May 25, 2023 at 09:45:11AM -0700, Paul E. McKenney wrote:
> On Thu, May 25, 2023 at 01:37:13AM +0800, kernel test robot wrote:
> > Hello,
> > 
> > kernel test robot noticed "BUG:kernel_NULL_pointer_dereference,address" on:
> > 
> > commit: 812195e4f70ef0e9fc68127355c553c537749546 ("rcuscale: Measure grace-period kthread CPU time")
> > https://git.kernel.org/cgit/linux/kernel/git/paulmck/linux-rcu.git dev.2023.05.20a
> > 
> > in testcase: boot
> > 
> > compiler: clang-14
> > test machine: qemu-system-x86_64 -enable-kvm -cpu SandyBridge -smp 2 -m 16G
> > 
> > (please refer to attached dmesg/kmsg for entire log/backtrace)
> > 
> > 
> > +---------------------------------------------+------------+------------+
> > |                                             | 2393139b67 | 812195e4f7 |
> > +---------------------------------------------+------------+------------+
> > | boot_successes                              | 8          | 0          |
> > | boot_failures                               | 0          | 8          |
> > | BUG:kernel_NULL_pointer_dereference,address | 0          | 8          |
> > | Oops:#[##]                                  | 0          | 8          |
> > | Kernel_panic-not_syncing:Fatal_exception    | 0          | 8          |
> > +---------------------------------------------+------------+------------+
> > 
> > 
> > If you fix the issue, kindly add following tag
> > | Reported-by: kernel test robot <yujie.liu@intel.com>
> > | Closes: https://lore.kernel.org/oe-lkp/202305241757.57c30887-yujie.liu@intel.com
> 
> This commmit has since been replaced by this one, which should fix this
> problem:
> 
> 60901dadfadc ("rcuscale: Measure grace-period kthread CPU time")
> 
> Please let me know if the problem still exists with that commit.

The problem is gone on commit 60901dadfadc. Thanks.

Tested-by: Yujie Liu <yujie.liu@intel.com>

=========================================================================================
compiler/kconfig/rootfs/sleep/tbox_group/testcase:
  clang-14/x86_64-randconfig-a015-20230522/debian-11.1-i386-20220923.cgz/300/vm-snb/boot

commit:
  812195e4f70e ("rcuscale: Measure grace-period kthread CPU time")  <-- old commit from dev.2023.05.20a branch
  60901dadfadc ("rcuscale: Measure grace-period kthread CPU time")  <-- new commit from rcu/next branch

812195e4f70ef0e9 60901dadfadcc152ae5cad7ebae
---------------- ---------------------------
       fail:runs  %reproduction    fail:runs
           |             |             |
          6:6         -100%            :7     dmesg.BUG:kernel_NULL_pointer_dereference,address
          6:6         -100%            :7     dmesg.Kernel_panic-not_syncing:Fatal_exception
          6:6         -100%            :7     dmesg.Oops:#[##]
          6:6         -100%            :7     dmesg.boot_failures

--
Best Regards,
Yujie