linux-kernel - [PATCH RFC tip/core/rcu 26/28] rcu: Add more information to the wrong-idle-task complaint

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Message-Id: <1320265849-5744-26-git-send-email-paulmck@linux.vnet.ibm.com>
Date:	Wed,  2 Nov 2011 13:30:47 -0700
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,
	patches@...aro.org, "Paul E. McKenney" <paul.mckenney@...aro.org>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
Subject: [PATCH RFC tip/core/rcu 26/28] rcu: Add more information to the wrong-idle-task complaint

From: Paul E. McKenney <paul.mckenney@...aro.org>

The current code just complains if the current task is not the idle task.
This commit therefore adds printing of the identity of the idle task.

Signed-off-by: Paul E. McKenney <paul.mckenney@...aro.org>
Signed-off-by: Paul E. McKenney <paulmck@...ux.vnet.ibm.com>
---
 kernel/rcutiny.c |   12 ++++++++++--
 kernel/rcutree.c |   12 ++++++++++--
 2 files changed, 20 insertions(+), 4 deletions(-)

diff --git a/kernel/rcutiny.c b/kernel/rcutiny.c
index e0df33f..f4e7bc3 100644
--- a/kernel/rcutiny.c
+++ b/kernel/rcutiny.c
@@ -66,10 +66,14 @@ static void rcu_idle_enter_common(long long oldval)
 	}
 	RCU_TRACE(trace_rcu_dyntick("Start", oldval, rcu_dynticks_nesting));
 	if (!idle_cpu(smp_processor_id())) {
-		WARN_ON_ONCE(1);	/* must be idle task! */
+		struct task_struct *idle = idle_task(smp_processor_id());
+
 		RCU_TRACE(trace_rcu_dyntick("Error on entry: not idle task",
 					    oldval, rcu_dynticks_nesting));
 		ftrace_dump(DUMP_ALL);
+		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! */
 	}
 	rcu_sched_qs(0); /* implies rcu_bh_qsctr_inc(0) */
 }
@@ -116,10 +120,14 @@ static void rcu_idle_exit_common(long long oldval)
 	}
 	RCU_TRACE(trace_rcu_dyntick("End", oldval, rcu_dynticks_nesting));
 	if (!idle_cpu(smp_processor_id())) {
-		WARN_ON_ONCE(1);	/* must be idle task! */
+		struct task_struct *idle = idle_task(smp_processor_id());
+
 		RCU_TRACE(trace_rcu_dyntick("Error on exit: not idle task",
 			  oldval, rcu_dynticks_nesting));
 		ftrace_dump(DUMP_ALL);
+		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! */
 	}
 }
 
diff --git a/kernel/rcutree.c b/kernel/rcutree.c
index cc04876..2a8d9a6 100644
--- a/kernel/rcutree.c
+++ b/kernel/rcutree.c
@@ -356,10 +356,14 @@ static void rcu_idle_enter_common(struct rcu_dynticks *rdtp, long long oldval)
 	}
 	trace_rcu_dyntick("Start", oldval, rdtp->dynticks_nesting);
 	if (!idle_cpu(smp_processor_id())) {
-		WARN_ON_ONCE(1);	/* must be idle task! */
+		struct task_struct *idle = idle_task(smp_processor_id());
+
 		trace_rcu_dyntick("Error on entry: not idle task",
 				   oldval, rdtp->dynticks_nesting);
 		ftrace_dump(DUMP_ALL);
+		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! */
 	}
 	/* CPUs seeing atomic_inc() must see prior RCU read-side crit sects */
 	smp_mb__before_atomic_inc();  /* See above. */
@@ -445,10 +449,14 @@ static void rcu_idle_exit_common(struct rcu_dynticks *rdtp, long long oldval)
 	WARN_ON_ONCE(!(atomic_read(&rdtp->dynticks) & 0x1));
 	trace_rcu_dyntick("End", oldval, rdtp->dynticks_nesting);
 	if (!idle_cpu(smp_processor_id())) {
-		WARN_ON_ONCE(1);	/* must be idle task! */
+		struct task_struct *idle = idle_task(smp_processor_id());
+
 		trace_rcu_dyntick("Error on exit: not idle task",
 				  oldval, rdtp->dynticks_nesting);
 		ftrace_dump(DUMP_ALL);
+		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! */
 	}
 }
 
-- 
1.7.3.2

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