Date:   Sat, 10 Oct 2020 11:03:22 -0700
From:   Rob Clark <robdclark@...il.com>
To:     linux-kernel@...r.kernel.org
Cc:     Rob Clark <robdclark@...omium.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Ingo Molnar <mingo@...hat.com>,
        "Peter Zijlstra (Intel)" <peterz@...radead.org>,
        Phil Auld <pauld@...hat.com>,
        Valentin Schneider <valentin.schneider@....com>,
        Thara Gopinath <thara.gopinath@...aro.org>,
        Randy Dunlap <rdunlap@...radead.org>,
        Vincent Donnefort <vincent.donnefort@....com>,
        Mel Gorman <mgorman@...hsingularity.net>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Jens Axboe <axboe@...nel.dk>,
        Marcelo Tosatti <mtosatti@...hat.com>,
        Frederic Weisbecker <frederic@...nel.org>,
        Ilias Stamatis <stamatis.iliass@...il.com>,
        Liang Chen <cl@...k-chips.com>,
        Ben Dooks <ben.dooks@...ethink.co.uk>,
        Peter Zijlstra <a.p.zijlstra@...llo.nl>,
        "J. Bruce Fields" <bfields@...hat.com>
Subject: [PATCH] kthread: Add kthread_work tracepoints

From: Rob Clark <robdclark@...omium.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@...omium.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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