linux-kernel - Re: [paulmck-rcu:dev.2023.05.20a] [rcuscale] 812195e4f7: BUG:kernel_NULL_pointer

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Date:   Fri, 26 May 2023 02:49:44 -0700
From:   "Paul E. McKenney" <paulmck@...nel.org>
To:     Yujie Liu <yujie.liu@...el.com>
Cc:     oe-lkp@...ts.linux.dev, lkp@...el.com,
        linux-kernel@...r.kernel.org, rcu@...r.kernel.org
Subject: Re: [paulmck-rcu:dev.2023.05.20a] [rcuscale] 812195e4f7:
 BUG:kernel_NULL_pointer_dereference,address

On Fri, May 26, 2023 at 03:59:48PM +0800, Yujie Liu wrote:
> 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@...el.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 This commmit has since been replaced by this one, which should fix this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@...el.com>

And thank you again for your testing efforts!

							Thanx, Paul

> =========================================================================================
> 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
>