[PATCH v1 2/2] x86, perf,cqm: handle CPU hotplug

Kanaka Juvva
2015-06-18T18:48:24Z

Added lock in event reader function. The cqm_pick_event_reader() function
accesses cqm_cpumask and it is critical section between this and
cqm_stable().

This situation is true when a CPU is hotplugged. Mutex is used to protect
the critical section.

Signed-off-by: Kanaka Juvva <kanaka.d.juvva@linux.intel.com>
---
arch/x86/kernel/cpu/perf_event_intel_cqm.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kernel/cpu/perf_event_intel_cqm.c b/arch/x86/kernel/cpu/perf_event_intel_cqm.c
index 1880761..e17e37f 100644
--- a/arch/x86/kernel/cpu/perf_event_intel_cqm.c
+++ b/arch/x86/kernel/cpu/perf_event_intel_cqm.c
@@ -1239,12 +1239,15 @@ static inline void cqm_pick_event_reader(int cpu)
int phys_id = topology_physical_package_id(cpu);
int i;

+ mutex_lock(&cache_mutex);
for_each_cpu(i, &cqm_cpumask) {
if (phys_id == topology_physical_package_id(i))
- return; /* already got reader for this socket */
+ goto out; /* already got reader for this socket */
}

cpumask_set_cpu(cpu, &cqm_cpumask);
+out:
+ mutex_unlock(&cache_mutex);
}

static void intel_cqm_cpu_prepare(unsigned int cpu)
--
2.1.0