linux-kernel - [PATCH 1/2] locking: Add lock contention tracepoints

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Date:   Tue, 22 Mar 2022 11:57:08 -0700
From:   Namhyung Kim <namhyung@...nel.org>
To:     Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...nel.org>, Will Deacon <will@...nel.org>,
        Waiman Long <longman@...hat.com>,
        Boqun Feng <boqun.feng@...il.com>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Steven Rostedt <rostedt@...dmis.org>,
        Byungchul Park <byungchul.park@....com>,
        "Paul E. McKenney" <paulmck@...nel.org>,
        Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
        Arnd Bergmann <arnd@...db.de>,
        Radoslaw Burny <rburny@...gle.com>, linux-arch@...r.kernel.org,
        bpf@...r.kernel.org, Hyeonggon Yoo <42.hyeyoo@...il.com>
Subject: [PATCH 1/2] locking: Add lock contention tracepoints

This adds two new lock contention tracepoints like below:

 * lock:contention_begin
 * lock:contention_end

The lock:contention_begin takes a flags argument to classify locks.  I
found it useful to identify what kind of locks it's tracing like if
it's spinning or sleeping, reader-writer lock, real-time, and per-cpu.

Move tracepoint definitions into mutex.c so that we can use them
without lockdep.

Tested-by: Hyeonggon Yoo <42.hyeyoo@...il.com>
Signed-off-by: Namhyung Kim <namhyung@...nel.org>
---
 include/trace/events/lock.h | 61 +++++++++++++++++++++++++++++++++++--
 kernel/locking/lockdep.c    |  1 -
 kernel/locking/mutex.c      |  3 ++
 3 files changed, 61 insertions(+), 4 deletions(-)

diff --git a/include/trace/events/lock.h b/include/trace/events/lock.h
index d7512129a324..b9b6e3edd518 100644
--- a/include/trace/events/lock.h
+++ b/include/trace/events/lock.h
@@ -5,11 +5,21 @@
 #if !defined(_TRACE_LOCK_H) || defined(TRACE_HEADER_MULTI_READ)
 #define _TRACE_LOCK_H
 
-#include <linux/lockdep.h>
+#include <linux/sched.h>
 #include <linux/tracepoint.h>
 
+/* flags for lock:contention_begin */
+#define LCB_F_SPIN	(1U << 0)
+#define LCB_F_READ	(1U << 1)
+#define LCB_F_WRITE	(1U << 2)
+#define LCB_F_RT	(1U << 3)
+#define LCB_F_PERCPU	(1U << 4)
+
+
 #ifdef CONFIG_LOCKDEP
 
+#include <linux/lockdep.h>
+
 TRACE_EVENT(lock_acquire,
 
 	TP_PROTO(struct lockdep_map *lock, unsigned int subclass,
@@ -78,8 +88,53 @@ DEFINE_EVENT(lock, lock_acquired,
 	TP_ARGS(lock, ip)
 );
 
-#endif
-#endif
+#endif /* CONFIG_LOCK_STAT */
+#endif /* CONFIG_LOCKDEP */
+
+TRACE_EVENT(contention_begin,
+
+	TP_PROTO(void *lock, unsigned int flags),
+
+	TP_ARGS(lock, flags),
+
+	TP_STRUCT__entry(
+		__field(void *, lock_addr)
+		__field(unsigned int, flags)
+	),
+
+	TP_fast_assign(
+		__entry->lock_addr = lock;
+		__entry->flags = flags;
+	),
+
+	TP_printk("%p (flags=%s)", __entry->lock_addr,
+		  __print_flags(__entry->flags, "|",
+				{ LCB_F_SPIN,		"SPIN" },
+				{ LCB_F_READ,		"READ" },
+				{ LCB_F_WRITE,		"WRITE" },
+				{ LCB_F_RT,		"RT" },
+				{ LCB_F_PERCPU,		"PERCPU" }
+			  ))
+);
+
+TRACE_EVENT(contention_end,
+
+	TP_PROTO(void *lock, int ret),
+
+	TP_ARGS(lock, ret),
+
+	TP_STRUCT__entry(
+		__field(void *, lock_addr)
+		__field(int, ret)
+	),
+
+	TP_fast_assign(
+		__entry->lock_addr = lock;
+		__entry->ret = ret;
+	),
+
+	TP_printk("%p (ret=%d)", __entry->lock_addr, __entry->ret)
+);
 
 #endif /* _TRACE_LOCK_H */
 
diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
index 50036c10b518..08f8fb6a2d1e 100644
--- a/kernel/locking/lockdep.c
+++ b/kernel/locking/lockdep.c
@@ -60,7 +60,6 @@
 
 #include "lockdep_internals.h"
 
-#define CREATE_TRACE_POINTS
 #include <trace/events/lock.h>
 
 #ifdef CONFIG_PROVE_LOCKING
diff --git a/kernel/locking/mutex.c b/kernel/locking/mutex.c
index 5e3585950ec8..ee2fd7614a93 100644
--- a/kernel/locking/mutex.c
+++ b/kernel/locking/mutex.c
@@ -30,6 +30,9 @@
 #include <linux/debug_locks.h>
 #include <linux/osq_lock.h>
 
+#define CREATE_TRACE_POINTS
+#include <trace/events/lock.h>
+
 #ifndef CONFIG_PREEMPT_RT
 #include "mutex.h"
 
-- 
2.35.1.894.gb6a874cedc-goog