linux-kernel - Re: [LKP] [rcutorture] 3b745c8969: WARNING:at_mm/slab_common.c:#kmalloc

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Date:   Thu, 26 Jul 2018 10:39:27 -0700
From:   Joel Fernandes <joel@...lfernandes.org>
To:     "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
Cc:     kernel test robot <rong.a.chen@...el.com>,
        LKML <linux-kernel@...r.kernel.org>,
        Stephen Rothwell <sfr@...b.auug.org.au>, lkp@...org
Subject: Re: [LKP] [rcutorture]  3b745c8969:
 WARNING:at_mm/slab_common.c:#kmalloc_slab

On Thu, Jul 26, 2018 at 04:53:25AM -0700, Paul E. McKenney wrote:
> On Thu, Jul 26, 2018 at 04:50:15PM +0800, kernel test robot wrote:
> > 
> > FYI, we noticed the following commit (built with gcc-5):
> > 
> > commit: 3b745c8969c752601cb68c82a06735363563ab42 ("rcutorture: Make boost test more robust")
> > https://git.kernel.org/cgit/linux/kernel/git/next/linux-next.git master
> > 
> > in testcase: boot
> > 
> > on test machine: qemu-system-x86_64 -enable-kvm -smp 2 -m 512M
> > 
> > caused below changes (please refer to attached dmesg/kmsg for entire log/backtrace):
> 
> Is this fixed by 4babd855fd61 ("rcutorture: Add support to detect
> if boost kthread prio is too low")?  That could address the
> rcu_torture_stats_print() failures, depending on exactly what they were.
> (Yes, I should have reversed these two commits, but they are in -tip
> now, so that ship has sailed.)
> 
> Joel, any other thoughts?

Last I tried to reproduce this issue on my setup, I wasn't able to. I can try
again to reproduct it in LKP today if you feel its a real issue triggered by
the rcutorture boost patches.

> That aside, the 450efca718 column has zeroes all the way down, so I do
> have some questions about that.  ;-)

Yes me too ;-) It seems quite odd all those columns show failures. Especially
the Kmalloc test failure and the warning in the enclosed dmesg log seems
nothing to do with the RCU boost patches.

Could it be a cascading effect of the failures where one failure triggers
another?

thanks!

 - Joel