From 4596749339e06dc7a424fc08a15eded850ed78b7 Mon Sep 17 00:00:00 2001 From: Samuel Neves Date: Wed, 21 Feb 2018 20:50:36 +0000 Subject: [PATCH] x86/topology: Update the 'cpu cores' field in /proc/cpuinfo correctly across CPU hotplug operations Without this fix, /proc/cpuinfo will display an incorrect amount of CPU cores, after bringing them offline and online again, as exemplified below: $ cat /proc/cpuinfo | grep cores cpu cores : 4 cpu cores : 8 cpu cores : 8 cpu cores : 20 cpu cores : 4 cpu cores : 3 cpu cores : 2 cpu cores : 2 This patch fixes this by always zeroing the booted_cores variable upon turning off a logical CPU. Tested-by: Dou Liyang Signed-off-by: Samuel Neves Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: jgross@suse.com Cc: luto@kernel.org Cc: prarit@redhat.com Cc: vkuznets@redhat.com Link: http://lkml.kernel.org/r/20180221205036.5244-1-sneves@dei.uc.pt Signed-off-by: Ingo Molnar --- arch/x86/kernel/smpboot.c | 1 + 1 file changed, 1 insertion(+) diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c index 9eee25d..ff99e2b 100644 --- a/arch/x86/kernel/smpboot.c +++ b/arch/x86/kernel/smpboot.c @@ -1437,6 +1437,7 @@ static void remove_siblinginfo(int cpu) cpumask_clear(topology_sibling_cpumask(cpu)); cpumask_clear(topology_core_cpumask(cpu)); c->cpu_core_id = 0; + c->booted_cores = 0; cpumask_clear_cpu(cpu, cpu_sibling_setup_mask); recompute_smt_state(); } -- 2.7.4