From: Nick Desaulniers <ndesaulniers@google.com> To: Marco Elver <elver@google.com> Cc: Kan Liang <kan.liang@linux.intel.com>, clang-built-linux <clang-built-linux@googlegroups.com>, kasan-dev <kasan-dev@googlegroups.com>, kernel test robot <rong.a.chen@intel.com>, Peter Zijlstra <peterz@infradead.org>, 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 10:49:08 -0700 [thread overview] Message-ID: <CAKwvOd=Gi2z_NjRfpTigCCcV5kUWU7Bm7h1eHLeQ6DZCmrsR8w@mail.gmail.com> (raw) In-Reply-To: <CANpmjNPcOHAE5d=gaD327HqxTBegf75qeN_pjoszahdk6_i5=Q@mail.gmail.com> On Mon, May 18, 2020 at 7:34 AM Marco Elver <elver@google.com> wrote: > > 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. Thanks for the report, testing, and bisection. I don't see any smoking gun in the code. https://godbolt.org/z/qbK26r > > 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. Can you share the disassembly of icx_uncore_mmio_init() in the given configuration? -- Thanks, ~Nick Desaulniers
WARNING: multiple messages have this Message-ID (diff)
From: Nick Desaulniers <ndesaulniers@google.com> To: lkp@lists.01.org Subject: Re: [rcu] 2f08469563: BUG:kernel_reboot-without-warning_in_boot_stage Date: Mon, 18 May 2020 10:49:08 -0700 [thread overview] Message-ID: <CAKwvOd=Gi2z_NjRfpTigCCcV5kUWU7Bm7h1eHLeQ6DZCmrsR8w@mail.gmail.com> (raw) In-Reply-To: <CANpmjNPcOHAE5d=gaD327HqxTBegf75qeN_pjoszahdk6_i5=Q@mail.gmail.com> [-- Attachment #1: Type: text/plain, Size: 3320 bytes --] On Mon, May 18, 2020 at 7:34 AM Marco Elver <elver@google.com> wrote: > > 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. Thanks for the report, testing, and bisection. I don't see any smoking gun in the code. https://godbolt.org/z/qbK26r > > 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. Can you share the disassembly of icx_uncore_mmio_init() in the given configuration? -- Thanks, ~Nick Desaulniers
next prev parent reply other threads:[~2020-05-18 17:49 UTC|newest] Thread overview: 22+ 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 1:17 ` kernel test robot 2020-05-17 3:47 ` Paul E. McKenney 2020-05-17 3:47 ` Paul E. McKenney 2020-05-18 10:11 ` Marco Elver 2020-05-18 10:11 ` Marco Elver 2020-05-18 12:44 ` Marco Elver 2020-05-18 12:44 ` Marco Elver 2020-05-18 14:34 ` Marco Elver 2020-05-18 14:34 ` Marco Elver 2020-05-18 17:49 ` Nick Desaulniers [this message] 2020-05-18 17:49 ` Nick Desaulniers 2020-05-18 18:05 ` Marco Elver 2020-05-18 18:05 ` Marco Elver 2020-05-19 10:16 ` Marco Elver 2020-05-19 10:16 ` Marco Elver 2020-05-19 13:40 ` Marco Elver 2020-05-19 13:40 ` Marco Elver 2020-05-19 18:32 ` Marco Elver 2020-05-19 18:32 ` Marco Elver 2020-05-20 16:32 ` Nick Desaulniers 2020-05-20 16:32 ` Nick Desaulniers
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