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From: Samuel Neves <sneves@dei.uc.pt>
To: tglx@linutronix.de, mingo@redhat.com, hpa@zytor.com,
	x86@kernel.org, jgross@suse.com, douly.fnst@cn.fujitsu.com,
	luto@kernel.org, prarit@redhat.com, ak@linux.intel.com,
	vkuznets@redhat.com, linux-kernel@vger.kernel.org
Cc: Samuel Neves <sneves@dei.uc.pt>
Subject: [PATCH] smpboot: correctly update number of booted cores
Date: Wed, 21 Feb 2018 20:50:36 +0000	[thread overview]
Message-ID: <20180221205036.5244-1-sneves@dei.uc.pt> (raw)

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.

Signed-off-by: Samuel Neves <sneves@dei.uc.pt>
---
 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 9eee25d07586..ff99e2b6fc54 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();
 }
-- 
2.14.3

             reply	other threads:[~2018-02-21 20:59 UTC|newest]

Thread overview: 3+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-02-21 20:50 Samuel Neves [this message]
2018-02-22  8:07 ` Dou Liyang
2018-02-23  8:29 ` [tip:x86/urgent] x86/topology: Update the 'cpu cores' field in /proc/cpuinfo correctly across CPU hotplug operations tip-bot for Samuel Neves

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