From: Marco Elver <elver@google.com>
To: kan.liang@linux.intel.com,
clang-built-linux <clang-built-linux@googlegroups.com>,
kasan-dev <kasan-dev@googlegroups.com>
Cc: kernel test robot <rong.a.chen@intel.com>,
Peter Zijlstra <peterz@infradead.org>,
Nick Desaulniers <ndesaulniers@google.com>,
LKML <linux-kernel@vger.kernel.org>, LKP <lkp@lists.01.org>,
"Paul E. McKenney" <paulmck@kernel.org>,
Dmitry Vyukov <dvyukov@google.com>,
Alexander Potapenko <glider@google.com>,
Andrey Konovalov <andreyknvl@google.com>
Subject: Re: [rcu] 2f08469563: BUG:kernel_reboot-without-warning_in_boot_stage
Date: Mon, 18 May 2020 16:34:07 +0200 [thread overview]
Message-ID: <CANpmjNPcOHAE5d=gaD327HqxTBegf75qeN_pjoszahdk6_i5=Q@mail.gmail.com> (raw)
In-Reply-To: <CANpmjNMx0+=Cac=WvHuzKb2zJvgNVvVxjo_W1wYWztywxDKeCQ@mail.gmail.com>
On Mon, 18 May 2020 at 14:44, Marco Elver <elver@google.com> wrote:
>
> [+Cc clang-built-linux FYI]
>
> On Mon, 18 May 2020 at 12:11, Marco Elver <elver@google.com> wrote:
> >
> > On Sun, 17 May 2020 at 05:47, Paul E. McKenney <paulmck@kernel.org> wrote:
> > >
> > > On Sun, May 17, 2020 at 09:17:32AM +0800, kernel test robot wrote:
> > > > Greeting,
> > > >
> > > > FYI, we noticed the following commit (built with clang-11):
> > > >
> > > > commit: 2f08469563550d15cb08a60898d3549720600eee ("rcu: Mark rcu_state.ncpus to detect concurrent writes")
> > > > https://git.kernel.org/cgit/linux/kernel/git/paulmck/linux-rcu.git dev.2020.05.14c
> > > >
> > > > in testcase: boot
> > > >
> > > > on test machine: qemu-system-x86_64 -enable-kvm -cpu SandyBridge -smp 2 -m 8G
> > > >
> > > > caused below changes (please refer to attached dmesg/kmsg for entire log/backtrace):
> > > >
> > > >
> > > >
> > > >
> > > > If you fix the issue, kindly add following tag
> > > > Reported-by: kernel test robot <rong.a.chen@intel.com>
> > > >
> > > >
> > > > [ 0.054943] BRK [0x05204000, 0x05204fff] PGTABLE
> > > > [ 0.061181] BRK [0x05205000, 0x05205fff] PGTABLE
> > > > [ 0.062403] BRK [0x05206000, 0x05206fff] PGTABLE
> > > > [ 0.065200] RAMDISK: [mem 0x7a247000-0x7fffffff]
> > > > [ 0.067344] ACPI: Early table checksum verification disabled
> > > > BUG: kernel reboot-without-warning in boot stage
> > >
> > > I am having some difficulty believing that this commit is at fault given
> > > that the .config does not list CONFIG_KCSAN=y, but CCing Marco Elver
> > > for his thoughts. Especially given that I have never built with clang-11.
> > >
> > > But this does invoke ASSERT_EXCLUSIVE_WRITER() in early boot from
> > > rcu_init(). Might clang-11 have objections to early use of this macro?
> >
> > The macro is a noop without KCSAN. I think the bisection went wrong.
> >
> > I am able to reproduce a reboot-without-warning when building with
> > Clang 11 and the provided config. I did a bisect, starting with v5.6
> > (good), and found this:
> > - Since v5.6, first bad commit is
> > 20e2aa812620439d010a3f78ba4e05bc0b3e2861 (Merge tag
> > 'perf-urgent-2020-04-12' of
> > git://git.kernel.org/pub/scm/linux/kernel//git/tip/tip)
> > - The actual commit that introduced the problem is
> > 2b3b76b5ec67568da4bb475d3ce8a92ef494b5de (perf/x86/intel/uncore: Add
> > Ice Lake server uncore support) -- reverting it fixes the problem.
Some more clues:
1. I should have noticed that this uses CONFIG_KASAN=y.
2. Something about function icx_uncore_mmio_init(). Making it a noop
also makes the issue go away.
3. Leaving icx_uncore_mmio_init() a noop but removing the 'static'
from icx_mmio_uncores also presents the issue. So this seems to be
something about how/where icx_mmio_uncores is allocated.
Thanks,
-- Marco
next prev parent reply other threads:[~2020-05-18 14:34 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-05-17 1:17 [rcu] 2f08469563: BUG:kernel_reboot-without-warning_in_boot_stage kernel test robot
2020-05-17 3:47 ` Paul E. McKenney
2020-05-18 10:11 ` Marco Elver
2020-05-18 12:44 ` Marco Elver
2020-05-18 14:34 ` Marco Elver [this message]
2020-05-18 17:49 ` Nick Desaulniers
2020-05-18 18:05 ` Marco Elver
2020-05-19 10:16 ` Marco Elver
2020-05-19 13:40 ` Marco Elver
2020-05-19 18:32 ` Marco Elver
2020-05-20 16:32 ` Nick Desaulniers
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