[PATCH v4 1/4] perf/core,x86: introduce sync_task_ctx() method at struct pmu

[Alexey Budankov]

Declare sync_task_ctx() methods at the generic and x86 specific
pmu types to bridge calls to platform specific pmu code on optimized
context switch path between equivalent task perf event contexts.

Signed-off-by: Alexey Budankov <alexey.budankov@xxxxxxxxxxxxxxx>
---
Changes in v4:
- marked sync_task_ctx() as the optional in code comments;
- renamed params of sync_task_ctx() to prev and next;

---
 arch/x86/events/perf_event.h | 8 ++++++++
 include/linux/perf_event.h   | 7 +++++++
 2 files changed, 15 insertions(+)

diff --git a/arch/x86/events/perf_event.h b/arch/x86/events/perf_event.h
index ecacfbf4ebc1..be78f2765f74 100644
--- a/arch/x86/events/perf_event.h
+++ b/arch/x86/events/perf_event.h
@@ -682,6 +682,14 @@ struct x86_pmu {
 	 */
 	atomic_t	lbr_exclusive[x86_lbr_exclusive_max];
 
+	/*
+	 * perf task context (i.e. struct perf_event_context::task_ctx_data) switch helper
+	 * to bridge calls from perf/core to perf/x86. See struct pmu::sync_task_ctx() usage
+	 * for examples;
+	 */
+	void		(*sync_task_ctx)(struct x86_perf_task_context *prev,
+					 struct x86_perf_task_context *next);
+
 	/*
 	 * AMD bits
 	 */
diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
index 587ae4d002f5..4b96b4a5ac03 100644
--- a/include/linux/perf_event.h
+++ b/include/linux/perf_event.h
@@ -410,6 +410,13 @@ struct pmu {
 	 */
 	size_t				task_ctx_size;
 
+	/*
+	 * PMU specific parts of task perf event context (i.e. ctx->task_ctx_data)
+	 * can be synchronized using this function. See Intel LBR callstack support
+	 * implementation and Perf core context switch handling callbacks for usage
+	 * examples.
+	 */
+	void (*sync_task_ctx)		(void *prev, void *next); /* optional */
 
 	/*
 	 * Set up pmu-private data structures for an AUX area
-- 
2.20.1