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Commit b8421da4 authored by Samuel Neves's avatar Samuel Neves Committed by Greg Kroah-Hartman
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x86/topology: Update the 'cpu cores' field in /proc/cpuinfo correctly across CPU hotplug operations 



[ Upstream commit 4596749339e06dc7a424fc08a15eded850ed78b7 ]

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: default avatarDou Liyang <douly.fnst@cn.fujitsu.com>
Signed-off-by: default avatarSamuel Neves <sneves@dei.uc.pt>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
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: default avatarIngo Molnar <mingo@kernel.org>
Signed-off-by: default avatarSasha Levin <alexander.levin@microsoft.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent afc5883b

arch/x86/kernel/smpboot.c

+1 −0
Original line number Diff line number Diff line
@@ -1497,6 +1497,7 @@ static void remove_siblinginfo(int cpu) 
	cpumask_clear(topology_core_cpumask(cpu));

	c->phys_proc_id = 0;

	c->cpu_core_id = 0;

	c->booted_cores = 0;

	cpumask_clear_cpu(cpu, cpu_sibling_setup_mask);

	recompute_smt_state();

}