[tip:x86/urgent] x86/topology: Update the 'cpu cores' field in /proc/cpuinfo correctly across CPU hotplug operations

[tip-bot for Samuel Neves]

Commit-ID:  4596749339e06dc7a424fc08a15eded850ed78b7
Gitweb: https://git.kernel.org/tip/4596749339e06dc7a424fc08a15eded850ed78b7
Author: Samuel Neves 
AuthorDate: Wed, 21 Feb 2018 20:50:36 +
Committer:  Ingo Molnar 
CommitDate: Fri, 23 Feb 2018 08:47:47 +0100

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: jgr...@suse.com
Cc: l...@kernel.org
Cc: pra...@redhat.com
Cc: vkuzn...@redhat.com
Link: http://lkml.kernel.org/r/20180221205036.5244-1-sne...@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 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();
 }

[tip:x86/urgent] x86/topology: Update the 'cpu cores' field in /proc/cpuinfo correctly across CPU hotplug operations

[tip-bot for Samuel Neves]

Commit-ID:  4596749339e06dc7a424fc08a15eded850ed78b7
Gitweb: https://git.kernel.org/tip/4596749339e06dc7a424fc08a15eded850ed78b7
Author: Samuel Neves 
AuthorDate: Wed, 21 Feb 2018 20:50:36 +
Committer:  Ingo Molnar 
CommitDate: Fri, 23 Feb 2018 08:47:47 +0100

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: jgr...@suse.com
Cc: l...@kernel.org
Cc: pra...@redhat.com
Cc: vkuzn...@redhat.com
Link: http://lkml.kernel.org/r/20180221205036.5244-1-sne...@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 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();
 }