From 7bb39313cd6239e7eb95198950a02b4ad2a08316 Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Wed, 23 Dec 2020 17:04:19 -0800 Subject: [PATCH] x86/mce: Make mce_timed_out() identify holdout CPUs 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 correlate with other hardware-oriented error messages. Add a cpumask of CPUs which maintains which CPUs have entered this handler, and print out which ones failed to enter in the event of a timeout. [ bp: Massage. ] Reported-by: Jonathan Lemon Signed-off-by: Paul E. McKenney Signed-off-by: Borislav Petkov Tested-by: Tony Luck Link: https://lkml.kernel.org/r/20210106174102.GA23874@paulmck-ThinkPad-P72 --- arch/x86/kernel/cpu/mce/core.c | 15 ++++++++++++++- 1 file changed, 14 insertions(+), 1 deletion(-) diff --git a/arch/x86/kernel/cpu/mce/core.c b/arch/x86/kernel/cpu/mce/core.c index 13d3f1cbda176..6c81d0998e0a3 100644 --- a/arch/x86/kernel/cpu/mce/core.c +++ b/arch/x86/kernel/cpu/mce/core.c @@ -877,6 +877,12 @@ static atomic_t mce_executing; */ static atomic_t mce_callin; +/* + * Track which CPUs entered the MCA broadcast synchronization and which not in + * order to print holdouts. + */ +static cpumask_t mce_missing_cpus = CPU_MASK_ALL; + /* * Check if a timeout waiting for other CPUs happened. */ @@ -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_and(&mce_missing_cpus, cpu_online_mask, &mce_missing_cpus)) + pr_emerg("CPUs not responding to MCE broadcast (may include false positives): %*pbl\n", + 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); + cpumask_clear_cpu(smp_processor_id(), &mce_missing_cpus); /* * Wait for everyone. @@ -1114,6 +1125,7 @@ static int mce_end(int order) reset: atomic_set(&global_nwo, 0); atomic_set(&mce_callin, 0); + cpumask_setall(&mce_missing_cpus); barrier(); /* @@ -2712,6 +2724,7 @@ static void mce_reset(void) atomic_set(&mce_executing, 0); atomic_set(&mce_callin, 0); atomic_set(&global_nwo, 0); + cpumask_setall(&mce_missing_cpus); } static int fake_panic_get(void *data, u64 *val) -- 2.39.5