[PATCH] kthread: Add kthread_work tracepoints

* [PATCH] kthread: Add kthread_work tracepoints
@ 2020-10-10 18:03 Rob Clark
  2020-10-12 13:59 ` Steven Rostedt
  0 siblings, 1 reply; 4+ messages in thread
From: Rob Clark @ 2020-10-10 18:03 UTC (permalink / raw)
  To: linux-kernel
  Cc: Rob Clark, Steven Rostedt, Ingo Molnar, Peter Zijlstra (Intel),
	Phil Auld, Valentin Schneider, Thara Gopinath, Randy Dunlap,
	Vincent Donnefort, Mel Gorman, Andrew Morton, Jens Axboe,
	Marcelo Tosatti, Frederic Weisbecker, Ilias Stamatis, Liang Chen,
	Ben Dooks, Peter Zijlstra, J. Bruce Fields

From: Rob Clark <robdclark@chromium.org>

While migrating some code from wq to kthread_worker, I found that I
missed the execute_start/end tracepoints.  So add similar tracepoints
for kthread_work.  And for completeness, queue_work tracepoint (although
this one differs slightly from the matching workqueue tracepoint).

Signed-off-by: Rob Clark <robdclark@chromium.org>
---
 include/trace/events/sched.h | 84 ++++++++++++++++++++++++++++++++++++
 kernel/kthread.c             |  9 ++++
 2 files changed, 93 insertions(+)

diff --git a/include/trace/events/sched.h b/include/trace/events/sched.h
index fec25b9cfbaf..349d9872e807 100644
--- a/include/trace/events/sched.h
+++ b/include/trace/events/sched.h
@@ -5,6 +5,7 @@
 #if !defined(_TRACE_SCHED_H) || defined(TRACE_HEADER_MULTI_READ)
 #define _TRACE_SCHED_H
 
+#include <linux/kthread.h>
 #include <linux/sched/numa_balancing.h>
 #include <linux/tracepoint.h>
 #include <linux/binfmts.h>
@@ -51,6 +52,89 @@ TRACE_EVENT(sched_kthread_stop_ret,
 	TP_printk("ret=%d", __entry->ret)
 );
 
+/**
+ * sched_kthread_work_queue_work - called when a work gets queued
+ * @worker:	pointer to the kthread_worker
+ * @work:	pointer to struct kthread_work
+ *
+ * This event occurs when a work is queued immediately or once a
+ * delayed work is actually queued (ie: once the delay has been
+ * reached).
+ */
+TRACE_EVENT(sched_kthread_work_queue_work,
+
+	TP_PROTO(struct kthread_worker *worker,
+		 struct kthread_work *work),
+
+	TP_ARGS(worker, work),
+
+	TP_STRUCT__entry(
+		__field( void *,	work	)
+		__field( void *,	function)
+		__field( void *,	worker)
+	),
+
+	TP_fast_assign(
+		__entry->work		= work;
+		__entry->function	= work->func;
+		__entry->worker		= worker;
+	),
+
+	TP_printk("work struct=%p function=%ps worker=%p",
+		  __entry->work, __entry->function, __entry->worker)
+);
+
+/**
+ * sched_kthread_work_execute_start - called immediately before the work callback
+ * @work:	pointer to struct kthread_work
+ *
+ * Allows to track kthread work execution.
+ */
+TRACE_EVENT(sched_kthread_work_execute_start,
+
+	TP_PROTO(struct kthread_work *work),
+
+	TP_ARGS(work),
+
+	TP_STRUCT__entry(
+		__field( void *,	work	)
+		__field( void *,	function)
+	),
+
+	TP_fast_assign(
+		__entry->work		= work;
+		__entry->function	= work->func;
+	),
+
+	TP_printk("work struct %p: function %ps", __entry->work, __entry->function)
+);
+
+/**
+ * sched_kthread_work_execute_end - called immediately after the work callback
+ * @work:	pointer to struct work_struct
+ * @function:   pointer to worker function
+ *
+ * Allows to track workqueue execution.
+ */
+TRACE_EVENT(sched_kthread_work_execute_end,
+
+	TP_PROTO(struct kthread_work *work, kthread_work_func_t function),
+
+	TP_ARGS(work, function),
+
+	TP_STRUCT__entry(
+		__field( void *,	work	)
+		__field( void *,	function)
+	),
+
+	TP_fast_assign(
+		__entry->work		= work;
+		__entry->function	= function;
+	),
+
+	TP_printk("work struct %p: function %ps", __entry->work, __entry->function)
+);
+
 /*
  * Tracepoint for waking up a task:
  */
diff --git a/kernel/kthread.c b/kernel/kthread.c
index 3edaa380dc7b..c1e59d6bf802 100644
--- a/kernel/kthread.c
+++ b/kernel/kthread.c
@@ -704,8 +704,15 @@ int kthread_worker_fn(void *worker_ptr)
 	raw_spin_unlock_irq(&worker->lock);
 
 	if (work) {
+		kthread_work_func_t func = work->func;
 		__set_current_state(TASK_RUNNING);
+		trace_sched_kthread_work_execute_start(work);
 		work->func(work);
+		/*
+		 * Avoid dereferencing work after this point.  The trace
+		 * event only cares about the address.
+		 */
+		trace_sched_kthread_work_execute_end(work, func);
 	} else if (!freezing(current))
 		schedule();
 
@@ -834,6 +841,8 @@ static void kthread_insert_work(struct kthread_worker *worker,
 {
 	kthread_insert_work_sanity_check(worker, work);
 
+	trace_sched_kthread_work_queue_work(worker, work);
+
 	list_add_tail(&work->node, pos);
 	work->worker = worker;
 	if (!worker->current_work && likely(worker->task))
-- 
2.26.2


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