linux-kernel - [PATCH tip/core/rcu 1/6] rcu: Consolidate dumping of ftrace buffer

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Date:	Tue, 12 Apr 2016 08:02:17 -0700
From:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To:	linux-kernel@...r.kernel.org
Cc:	mingo@...nel.org, jiangshanlai@...il.com, dipankar@...ibm.com,
	akpm@...ux-foundation.org, mathieu.desnoyers@...icios.com,
	josh@...htriplett.org, tglx@...utronix.de, peterz@...radead.org,
	rostedt@...dmis.org, dhowells@...hat.com, edumazet@...gle.com,
	dvhart@...ux.intel.com, fweisbec@...il.com, oleg@...hat.com,
	bobby.prani@...il.com,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
Subject: [PATCH tip/core/rcu 1/6] rcu: Consolidate dumping of ftrace buffer

This commit consolidates a couple definitions and several calls for
single-shot ftrace-buffer dumping.

Signed-off-by: Paul E. McKenney <paulmck@...ux.vnet.ibm.com>
---
 include/linux/rcupdate.h | 13 +++++++++++++
 kernel/rcu/rcutorture.c  | 17 +++--------------
 kernel/rcu/tree.c        |  4 ++--
 3 files changed, 18 insertions(+), 16 deletions(-)

diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h
index 2657aff2725b..45de591657a6 100644
--- a/include/linux/rcupdate.h
+++ b/include/linux/rcupdate.h
@@ -1144,4 +1144,17 @@ static inline void rcu_sysidle_force_exit(void)
 #endif /* #else #ifdef CONFIG_NO_HZ_FULL_SYSIDLE */
 
 
+/*
+ * Dump the ftrace buffer, but only one time per callsite per boot.
+ */
+#define rcu_ftrace_dump(oops_dump_mode) \
+do { \
+	static atomic_t ___rfd_beenhere = ATOMIC_INIT(0); \
+	\
+	if (!atomic_read(&___rfd_beenhere) && \
+	    !atomic_xchg(&___rfd_beenhere, 1)) \
+		ftrace_dump(oops_dump_mode); \
+} while (0)
+
+
 #endif /* __LINUX_RCUPDATE_H */
diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c
index 250ea67c1615..463867c43221 100644
--- a/kernel/rcu/rcutorture.c
+++ b/kernel/rcu/rcutorture.c
@@ -1082,17 +1082,6 @@ rcu_torture_fakewriter(void *arg)
 	return 0;
 }
 
-static void rcutorture_trace_dump(void)
-{
-	static atomic_t beenhere = ATOMIC_INIT(0);
-
-	if (atomic_read(&beenhere))
-		return;
-	if (atomic_xchg(&beenhere, 1) != 0)
-		return;
-	ftrace_dump(DUMP_ALL);
-}
-
 /*
  * RCU torture reader from timer handler.  Dereferences rcu_torture_current,
  * incrementing the corresponding element of the pipeline array.  The
@@ -1142,7 +1131,7 @@ static void rcu_torture_timer(unsigned long unused)
 	if (pipe_count > 1) {
 		do_trace_rcu_torture_read(cur_ops->name, &p->rtort_rcu, ts,
 					  started, completed);
-		rcutorture_trace_dump();
+		rcu_ftrace_dump(DUMP_ALL);
 	}
 	__this_cpu_inc(rcu_torture_count[pipe_count]);
 	completed = completed - started;
@@ -1215,7 +1204,7 @@ rcu_torture_reader(void *arg)
 		if (pipe_count > 1) {
 			do_trace_rcu_torture_read(cur_ops->name, &p->rtort_rcu,
 						  ts, started, completed);
-			rcutorture_trace_dump();
+			rcu_ftrace_dump(DUMP_ALL);
 		}
 		__this_cpu_inc(rcu_torture_count[pipe_count]);
 		completed = completed - started;
@@ -1333,7 +1322,7 @@ rcu_torture_stats_print(void)
 			 rcu_torture_writer_state,
 			 gpnum, completed, flags);
 		show_rcu_gp_kthreads();
-		rcutorture_trace_dump();
+		rcu_ftrace_dump(DUMP_ALL);
 	}
 	rtcv_snap = rcu_torture_current_version;
 }
diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index 9a535a86e732..531a328076bd 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -637,7 +637,7 @@ static void rcu_eqs_enter_common(long long oldval, bool user)
 			idle_task(smp_processor_id());
 
 		trace_rcu_dyntick(TPS("Error on entry: not idle task"), oldval, 0);
-		ftrace_dump(DUMP_ORIG);
+		rcu_ftrace_dump(DUMP_ORIG);
 		WARN_ONCE(1, "Current pid: %d comm: %s / Idle pid: %d comm: %s",
 			  current->pid, current->comm,
 			  idle->pid, idle->comm); /* must be idle task! */
@@ -799,7 +799,7 @@ static void rcu_eqs_exit_common(long long oldval, int user)
 
 		trace_rcu_dyntick(TPS("Error on exit: not idle task"),
 				  oldval, rdtp->dynticks_nesting);
-		ftrace_dump(DUMP_ORIG);
+		rcu_ftrace_dump(DUMP_ORIG);
 		WARN_ONCE(1, "Current pid: %d comm: %s / Idle pid: %d comm: %s",
 			  current->pid, current->comm,
 			  idle->pid, idle->comm); /* must be idle task! */
-- 
2.5.2