[PATCH 27/32] locking/lockdep: Remove redundant softirqs on check

From: Frederic Weisbecker <frederic@kernel.org>
To: LKML <linux-kernel@vger.kernel.org>
Cc: Frederic Weisbecker <frederic@kernel.org>,
	Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
	Peter Zijlstra <peterz@infradead.org>,
	Mauro Carvalho Chehab <mchehab@s-opensource.com>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	"David S . Miller" <davem@davemloft.net>,
	Thomas Gleixner <tglx@linutronix.de>,
	"Paul E . McKenney" <paulmck@linux.vnet.ibm.com>,
	Frederic Weisbecker <fweisbec@gmail.com>,
	Pavan Kondeti <pkondeti@codeaurora.org>,
	Ingo Molnar <mingo@kernel.org>,
	Joel Fernandes <joel@joelfernandes.org>
Subject: [PATCH 27/32] locking/lockdep: Remove redundant softirqs on check
Date: Tue, 12 Feb 2019 18:14:18 +0100	[thread overview]
Message-ID: <20190212171423.8308-28-frederic@kernel.org> (raw)
In-Reply-To: <20190212171423.8308-1-frederic@kernel.org>

It makes no more sense to check for redundant softirqs on because
trace_softirqs_on() is no more symmetrical to trace_softirqs_off().

Indeed trace_softirqs_off() is called whenever we know that all softirq
vectors have been disabled. And trace_softirqs_on() is called everytime
we enable at least one vector. So curr->softirqs_enabled may well remain
true throughout subsequent calls.

FIXME: Perhaps we should rename those functions. Another solution would
be to make curr->softirqs_enabled to record the last value of
local_softirqs_enabled() so we could track again redundant calls.

Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Cc: Mauro Carvalho Chehab <mchehab@s-opensource.com>
Cc: Joel Fernandes <joel@joelfernandes.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Pavan Kondeti <pkondeti@codeaurora.org>
Cc: Paul E . McKenney <paulmck@linux.vnet.ibm.com>
Cc: David S . Miller <davem@davemloft.net>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
---
 kernel/locking/lockdep.c           | 5 -----
 kernel/locking/lockdep_internals.h | 1 -
 kernel/locking/lockdep_proc.c      | 2 +-
 3 files changed, 1 insertion(+), 7 deletions(-)

diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
index 6a74b433fe4c..9bb39677fd97 100644
--- a/kernel/locking/lockdep.c
+++ b/kernel/locking/lockdep.c
@@ -2976,11 +2976,6 @@ void trace_softirqs_on(unsigned long ip)
 	if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
 		return;
 
-	if (curr->softirqs_enabled) {
-		debug_atomic_inc(redundant_softirqs_on);
-		return;
-	}
-
 	current->lockdep_recursion = 1;
 	/*
 	 * We'll do an OFF -> ON transition:
diff --git a/kernel/locking/lockdep_internals.h b/kernel/locking/lockdep_internals.h
index 4b0c03f0f7ce..3401e4a91afb 100644
--- a/kernel/locking/lockdep_internals.h
+++ b/kernel/locking/lockdep_internals.h
@@ -186,7 +186,6 @@ struct lockdep_stats {
 	int	redundant_hardirqs_off;
 	int	softirqs_on_events;
 	int	softirqs_off_events;
-	int	redundant_softirqs_on;
 	int	redundant_softirqs_off;
 	int	nr_unused_locks;
 	int	nr_redundant_checks;
diff --git a/kernel/locking/lockdep_proc.c b/kernel/locking/lockdep_proc.c
index 3d31f9b0059e..4157560b36d2 100644
--- a/kernel/locking/lockdep_proc.c
+++ b/kernel/locking/lockdep_proc.c
@@ -169,7 +169,7 @@ static void lockdep_stats_debug_show(struct seq_file *m)
 			   hr2 = debug_atomic_read(redundant_hardirqs_off),
 			   si1 = debug_atomic_read(softirqs_on_events),
 			   si2 = debug_atomic_read(softirqs_off_events),
-			   sr1 = debug_atomic_read(redundant_softirqs_on),
+			   sr1 = 0,
 			   sr2 = debug_atomic_read(redundant_softirqs_off);
 
 	seq_printf(m, " chain lookup misses:           %11llu\n",
-- 
2.17.1

