[tip:perf/urgent] perf/x86/intel: Handle exclusive threadid correctly on CPU hotplug

[tip-bot for Zhou Chengming <tipbot@zytor.com>]

Commit-ID:  4e71de7986386d5fd3765458f27d612931f27f5e
Gitweb:     http://git.kernel.org/tip/4e71de7986386d5fd3765458f27d612931f27f5e
Author:     Zhou Chengming <zhouchengming1@huawei.com>
AuthorDate: Mon, 16 Jan 2017 11:21:11 +0800
Committer:  Thomas Gleixner <tglx@linutronix.de>
CommitDate: Tue, 17 Jan 2017 11:08:36 +0100

perf/x86/intel: Handle exclusive threadid correctly on CPU hotplug

The CPU hotplug function intel_pmu_cpu_starting() sets
cpu_hw_events.excl_thread_id unconditionally to 1 when the shared exclusive
counters data structure is already availabe for the sibling thread.

This works during the boot process because the first sibling gets threadid
0 assigned and the second sibling which shares the data structure gets 1.

But when the first thread of the core is offlined and onlined again it
shares the data structure with the second thread and gets exclusive thread
id 1 assigned as well.

Prevent this by checking the threadid of the already online thread.

[ tglx: Rewrote changelog ]

Signed-off-by: Zhou Chengming <zhouchengming1@huawei.com>
Cc: NuoHan Qiao <qiaonuohan@huawei.com>
Cc: ak@linux.intel.com
Cc: peterz@infradead.org
Cc: kan.liang@intel.com
Cc: dave.hansen@linux.intel.com
Cc: eranian@google.com
Cc: qiaonuohan@huawei.com
Cc: davidcc@google.com
Cc: guohanjun@huawei.com
Link: http://lkml.kernel.org/r/1484536871-3131-1-git-send-email-zhouchengming1@huawei.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
---					---
 arch/x86/events/intel/core.c |    7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

---
 arch/x86/events/intel/core.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/arch/x86/events/intel/core.c b/arch/x86/events/intel/core.c
index d611cab..eb1484c 100644
--- a/arch/x86/events/intel/core.c
+++ b/arch/x86/events/intel/core.c
@@ -3176,13 +3176,16 @@ static void intel_pmu_cpu_starting(int cpu)
 
 	if (x86_pmu.flags & PMU_FL_EXCL_CNTRS) {
 		for_each_cpu(i, topology_sibling_cpumask(cpu)) {
+			struct cpu_hw_events *sibling;
 			struct intel_excl_cntrs *c;
 
-			c = per_cpu(cpu_hw_events, i).excl_cntrs;
+			sibling = &per_cpu(cpu_hw_events, i);
+			c = sibling->excl_cntrs;
 			if (c && c->core_id == core_id) {
 				cpuc->kfree_on_online[1] = cpuc->excl_cntrs;
 				cpuc->excl_cntrs = c;
-				cpuc->excl_thread_id = 1;
+				if (!sibling->excl_thread_id)
+					cpuc->excl_thread_id = 1;
 				break;
 			}
 		}