On Wed, Jan 06, 2021 at 09:41:02AM -0800, Paul E. McKenney wrote:
> The "Timeout: Not all CPUs entered broadcast exception handler" message
> will appear from time to time given enough systems, but this message does
> not identify which CPUs failed to enter the broadcast exception handler.
> This information would be valuable if available, for example, in order to
> correlated with other hardware-oriented error messages.
Because you're expecting that the CPUs which have not entered the
exception handler might have stuck earlier and that's the correlation
there?
> This commit
That's a tautology. :)
> therefore maintains a cpumask_t of CPUs that have entered this handler,
> and prints out which ones failed to enter in the event of a timeout.
> Build-tested only.
>
> Cc: Tony Luck <tony.l...@intel.com>
> Cc: Borislav Petkov <b...@alien8.de>
> Cc: Thomas Gleixner <t...@linutronix.de>
> Cc: Ingo Molnar <mi...@redhat.com>
> Cc: "H. Peter Anvin" <h...@zytor.com>
> Cc: <x...@kernel.org>
> Cc: <linux-e...@vger.kernel.org>
> Reported-by: Jonathan Lemon <b...@fb.com>
> Signed-off-by: Paul E. McKenney <paul...@kernel.org>
>
> diff --git a/arch/x86/kernel/cpu/mce/core.c b/arch/x86/kernel/cpu/mce/core.c
> index 13d3f1c..44d2b99 100644
> --- a/arch/x86/kernel/cpu/mce/core.c
> +++ b/arch/x86/kernel/cpu/mce/core.c
> @@ -878,6 +878,12 @@ static atomic_t mce_executing;
> static atomic_t mce_callin;
>
> /*
> + * Track which CPUs entered and not in order to print holdouts.
> + */
> +static cpumask_t mce_present_cpus;
> +static cpumask_t mce_missing_cpus;
> +
> +/*
> * Check if a timeout waiting for other CPUs happened.
> */
> static int mce_timed_out(u64 *t, const char *msg)
> @@ -894,8 +900,12 @@ static int mce_timed_out(u64 *t, const char *msg)
> if (!mca_cfg.monarch_timeout)
> goto out;
> if ((s64)*t < SPINUNIT) {
> - if (mca_cfg.tolerant <= 1)
> + if (mca_cfg.tolerant <= 1) {
> + if (!cpumask_andnot(&mce_missing_cpus, cpu_online_mask,
> &mce_present_cpus))
> + pr_info("%s: MCE holdout CPUs: %*pbl\n",
> + __func__,
> cpumask_pr_args(&mce_missing_cpus));
> mce_panic(msg, NULL, NULL);
> + }
> cpu_missing = 1;
> return 1;
> }
> @@ -1006,6 +1016,7 @@ static int mce_start(int *no_way_out)
> * is updated before mce_callin.
> */
> order = atomic_inc_return(&mce_callin);
Doesn't a single mce_callin_mask suffice?
--
Regards/Gruss,
Boris.
https://people.kernel.org/tglx/notes-about-netiquette
