[RFC 3/5] perf: adds a new pmu-initialization-call

[Hans Rosenfeld <hans.rosenfeld@amd.com>]

From: Benjamin Block <benjamin.block@amd.com>

Adds a new call to the PMU-functions, which can be used by PMUs who
need information about the task and/or CPU for which the event shall
be initialized.

Signed-off-by: Benjamin Block <benjamin.block@amd.com>
Signed-off-by: Hans Rosenfeld <hans.rosenfeld@amd.com>
---
 include/linux/perf_event.h |    2 ++
 kernel/events/core.c       |   17 +++++++++++++----
 2 files changed, 15 insertions(+), 4 deletions(-)

diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
index 81807bd..0c6fae6 100644
--- a/include/linux/perf_event.h
+++ b/include/linux/perf_event.h
@@ -630,6 +630,8 @@ struct pmu {
 	 * Should return -ENOENT when the @event doesn't match this PMU.
 	 */
 	int (*event_init)		(struct perf_event *event);
+	int (*event_init_for)		(struct perf_event *event, int cpu,
+					 struct task_struct *task);
 
 #define PERF_EF_START	0x01		/* start the counter when adding    */
 #define PERF_EF_RELOAD	0x02		/* reload the counter when starting */
diff --git a/kernel/events/core.c b/kernel/events/core.c
index faf52f7..fd18d70 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -5746,7 +5746,8 @@ void perf_pmu_unregister(struct pmu *pmu)
 	free_pmu_context(pmu);
 }
 
-struct pmu *perf_init_event(struct perf_event *event)
+struct pmu *perf_init_event(struct perf_event *event, int cpu,
+			    struct task_struct *task)
 {
 	struct pmu *pmu = NULL;
 	int idx;
@@ -5758,14 +5759,22 @@ struct pmu *perf_init_event(struct perf_event *event)
 	pmu = idr_find(&pmu_idr, event->attr.type);
 	rcu_read_unlock();
 	if (pmu) {
-		ret = pmu->event_init(event);
+		if (pmu->event_init_for)
+			ret = pmu->event_init_for(event, cpu, task);
+		else
+			ret = pmu->event_init(event);
+
 		if (ret)
 			pmu = ERR_PTR(ret);
 		goto unlock;
 	}
 
 	list_for_each_entry_rcu(pmu, &pmus, entry) {
-		ret = pmu->event_init(event);
+		if (pmu->event_init_for)
+			ret = pmu->event_init_for(event, cpu, task);
+		else
+			ret = pmu->event_init(event);
+
 		if (!ret)
 			goto unlock;
 
@@ -5875,7 +5884,7 @@ perf_event_alloc(struct perf_event_attr *attr, int cpu,
 	if (attr->inherit && (attr->read_format & PERF_FORMAT_GROUP))
 		goto done;
 
-	pmu = perf_init_event(event);
+	pmu = perf_init_event(event, cpu, task);
 
 done:
 	err = 0;
-- 
1.7.7