linux-kernel - [PATCH tip/core/rcu 41/47] rcu: Trace only after NULL-pointer check

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Date:	Fri,  3 Feb 2012 17:45:16 -0800
From:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To:	linux-kernel@...r.kernel.org
Cc:	mingo@...e.hu, laijs@...fujitsu.com, dipankar@...ibm.com,
	akpm@...ux-foundation.org, mathieu.desnoyers@...ymtl.ca,
	josh@...htriplett.org, niv@...ibm.com, tglx@...utronix.de,
	peterz@...radead.org, rostedt@...dmis.org, Valdis.Kletnieks@...edu,
	dhowells@...hat.com, eric.dumazet@...il.com, darren@...art.com,
	fweisbec@...il.com, patches@...aro.org,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
Subject: [PATCH tip/core/rcu 41/47] rcu: Trace only after NULL-pointer check

From: "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>

Fix a bonehead error introduced when adding event tracing to rcutorture.
Move the traces to follow the NULL-pointer checks.

Signed-off-by: Paul E. McKenney <paulmck@...ux.vnet.ibm.com>
---
 kernel/rcutorture.c |    4 ++--
 1 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/kernel/rcutorture.c b/kernel/rcutorture.c
index c27862b..fdac008 100644
--- a/kernel/rcutorture.c
+++ b/kernel/rcutorture.c
@@ -1000,12 +1000,12 @@ static void rcu_torture_timer(unsigned long unused)
 				  rcu_read_lock_bh_held() ||
 				  rcu_read_lock_sched_held() ||
 				  srcu_read_lock_held(&srcu_ctl));
-	do_trace_rcu_torture_read(cur_ops->name, &p->rtort_rcu);
 	if (p == NULL) {
 		/* Leave because rcu_torture_writer is not yet underway */
 		cur_ops->readunlock(idx);
 		return;
 	}
+	do_trace_rcu_torture_read(cur_ops->name, &p->rtort_rcu);
 	if (p->rtort_mbtest == 0)
 		atomic_inc(&n_rcu_torture_mberror);
 	spin_lock(&rand_lock);
@@ -1063,13 +1063,13 @@ rcu_torture_reader(void *arg)
 					  rcu_read_lock_bh_held() ||
 					  rcu_read_lock_sched_held() ||
 					  srcu_read_lock_held(&srcu_ctl));
-		do_trace_rcu_torture_read(cur_ops->name, &p->rtort_rcu);
 		if (p == NULL) {
 			/* Wait for rcu_torture_writer to get underway */
 			cur_ops->readunlock(idx);
 			schedule_timeout_interruptible(HZ);
 			continue;
 		}
+		do_trace_rcu_torture_read(cur_ops->name, &p->rtort_rcu);
 		if (p->rtort_mbtest == 0)
 			atomic_inc(&n_rcu_torture_mberror);
 		cur_ops->read_delay(&rand);
-- 
1.7.8

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