[PATCH 3/9] perf: Introduce perf_pmu_migrate_context

Yan, Zheng
2012-05-02T02:07:52Z

From: "Yan, Zheng" <zheng.z.yan@intel.com>

Originally from Peter Zijlstra. The helper migrates perf events
from one cpu to another cpu.

Signed-off-by: Zheng Yan <zheng.z.yan@intel.com>
---
include/linux/perf_event.h | 2 ++
kernel/events/core.c | 36 ++++++++++++++++++++++++++++++++++++
2 files changed, 38 insertions(+), 0 deletions(-)

diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
index ddbb6a9..13b7b2d 100644
--- a/include/linux/perf_event.h
+++ b/include/linux/perf_event.h
@@ -1106,6 +1106,8 @@ perf_event_create_kernel_counter(struct perf_event_attr *attr,
struct task_struct *task,
perf_overflow_handler_t callback,
void *context);
+extern void perf_pmu_migrate_context(struct pmu *pmu,
+ int src_cpu, int dst_cpu);
extern u64 perf_event_read_value(struct perf_event *event,
u64 *enabled, u64 *running);

diff --git a/kernel/events/core.c b/kernel/events/core.c
index 84911de..1fc7000 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -1641,6 +1641,8 @@ perf_install_in_context(struct perf_event_context *ctx,
lockdep_assert_held(&ctx->mutex);

event->ctx = ctx;
+ if (event->cpu != -1)
+ event->cpu = cpu;

if (!task) {
/*
@@ -6377,6 +6379,7 @@ SYSCALL_DEFINE5(perf_event_open,
mutex_lock(&ctx->mutex);

if (move_group) {
+ synchronize_rcu();
perf_install_in_context(ctx, group_leader, event->cpu);
get_ctx(ctx);
list_for_each_entry(sibling, &group_leader->sibling_list,
@@ -6482,6 +6485,39 @@ perf_event_create_kernel_counter(struct perf_event_attr *attr, int cpu,
}
EXPORT_SYMBOL_GPL(perf_event_create_kernel_counter);

+void perf_pmu_migrate_context(struct pmu *pmu, int src_cpu, int dst_cpu)
+{
+ struct perf_event_context *src_ctx;
+ struct perf_event_context *dst_ctx;
+ struct perf_event *event, *tmp;
+ LIST_HEAD(events);
+
+ src_ctx = &per_cpu_ptr(pmu->pmu_cpu_context, src_cpu)->ctx;
+ dst_ctx = &per_cpu_ptr(pmu->pmu_cpu_context, dst_cpu)->ctx;
+
+ mutex_lock(&src_ctx->mutex);
+ list_for_each_entry_safe(event, tmp, &src_ctx->event_list,
+ event_entry) {
+ perf_remove_from_context(event);
+ put_ctx(src_ctx);
+ list_add(&event->event_entry, &events);
+ }
+ mutex_unlock(&src_ctx->mutex);
+
+ synchronize_rcu();
+
+ mutex_lock(&dst_ctx->mutex);
+ list_for_each_entry_safe(event, tmp, &events, event_entry) {
+ list_del(&event->event_entry);
+ if (event->state >= PERF_EVENT_STATE_OFF)
+ event->state = PERF_EVENT_STATE_INACTIVE;
+ perf_install_in_context(dst_ctx, event, dst_cpu);
+ get_ctx(dst_ctx);
+ }
+ mutex_unlock(&dst_ctx->mutex);
+}
+EXPORT_SYMBOL_GPL(perf_pmu_migrate_context);
+
static void sync_child_event(struct perf_event *child_event,
struct task_struct *child)
{
--
1.7.7.6