[PATCH 11/19] tracing/workqueue: turn workfunc_stats::inserted into unsigned int

[Frederic Weisbecker]

From: Zhaolei <zhaolei@xxxxxxxxxxxxxx>

struct workfunc_stats belongs to per_cpu struct of cpu_workqueue_stats,
which means we only need to serialize its access from one cpu.

And because trace_workqueue_insertion() is already inside a section
protected by the cpu workqueue lock, we can safely convert it into an
unsigned int.

[ Impact: locking cleanup]

Reported-by: Oleg Nesterov <oleg@xxxxxxxxxx>
Signed-off-by: Zhao Lei <zhaolei@xxxxxxxxxxxxxx>
Cc: Steven Rostedt <rostedt@xxxxxxxxxxx>
Cc: Tom Zanussi <tzanussi@xxxxxxxxx>
Cc: KOSAKI Motohiro <kosaki.motohiro@xxxxxxxxxxxxxx>
Cc: Oleg Nesterov <oleg@xxxxxxxxxx>
Signed-off-by: Frederic Weisbecker <fweisbec@xxxxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
 kernel/trace/trace_workqueue.c |   13 +++++--------
 1 files changed, 5 insertions(+), 8 deletions(-)

diff --git a/kernel/trace/trace_workqueue.c b/kernel/trace/trace_workqueue.c
index 69ae4aa..7a07d17 100644
--- a/kernel/trace/trace_workqueue.c
+++ b/kernel/trace/trace_workqueue.c
@@ -20,12 +20,9 @@ struct workfunc_stats {
 
 	/* Addr of worklet's callback function */
 	work_func_t			func;
-	/* Can be inserted on different workqueues, need to be atomic */
-	atomic_t			inserted;
-	/*
-	 * Don't need to be atomic, works are serialized in a single workqueue
-	 * thread on a single CPU.
-	 */
+
+	/* Protected by cpu workqueue lock */
+	unsigned int			inserted;
 	unsigned int			executed;
 };
 
@@ -80,7 +77,7 @@ int do_worklet_enqueue(struct cpu_workqueue_stats *cws,
 
 	list_add_tail(&wfstat->list, &cws->workfunclist);
 found:
-	atomic_inc(&wfstat->inserted);
+	wfstat->inserted++;
 
 	return 0;
 }
@@ -331,7 +328,7 @@ static int workqueue_stat_show(struct seq_file *s, void *p)
 		int lastwf = list_is_last(&wfstat->list, &cws->workfunclist);
 		seq_printf(s, "%3d %6d     %6u        %c-%pF\n",
 			cws->cpu,
-			atomic_read(&wfstat->inserted),
+			wfstat->inserted,
 			wfstat->executed,
 			lastwf ? '`' : '|',
 			wfstat->func);
-- 
1.6.2.3

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