Messages in this thread | | | From | Marco Elver <> | Date | Mon, 18 May 2020 12:11:06 +0200 | Subject | Re: [rcu] 2f08469563: BUG:kernel_reboot-without-warning_in_boot_stage |
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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.
Thanks, -- Marco
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