From 20e5f35dd3652eedb0d324398e2105be7b4fa547 Mon Sep 17 00:00:00 2001
From: Thomas Gleixner <tglx@linutronix.de>
Date: Sun, 17 Jul 2011 18:51:23 +0200
Subject: [PATCH 079/184] lockdep: Make it RT aware

There is not really a softirq context on PREEMPT_RT.
Softirqs on PREEMPT_RT are always invoked within the context of a threaded
interrupt handler or within ksoftirqd. The "in-softirq" context is preemptible
and is protected by a per-CPU lock to ensure mutual exclusion.

There is no difference on PREEMPT_RT between spin_lock_irq() and spin_lock()
because the former does not disable interrupts. Therefore if lock is used
in_softirq() and locked once with spin_lock_irq() then lockdep will report this
with "inconsistent {SOFTIRQ-ON-W} -> {IN-SOFTIRQ-W} usage".

Teach lockdep that we don't really do softirqs on -RT.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
---
 include/linux/irqflags.h | 23 +++++++++++++++--------
 kernel/locking/lockdep.c |  2 ++
 2 files changed, 17 insertions(+), 8 deletions(-)

diff --git a/include/linux/irqflags.h b/include/linux/irqflags.h
index c4288c7ae613f..2e09c269bf9d8 100644
--- a/include/linux/irqflags.h
+++ b/include/linux/irqflags.h
@@ -72,14 +72,6 @@ do {						\
 do {						\
 	__this_cpu_dec(hardirq_context);	\
 } while (0)
-# define lockdep_softirq_enter()		\
-do {						\
-	current->softirq_context++;		\
-} while (0)
-# define lockdep_softirq_exit()			\
-do {						\
-	current->softirq_context--;		\
-} while (0)
 
 # define lockdep_hrtimer_enter(__hrtimer)		\
 ({							\
@@ -141,6 +133,21 @@ do {						\
 # define lockdep_irq_work_exit(__work)		do { } while (0)
 #endif
 
+#if defined(CONFIG_TRACE_IRQFLAGS) && !defined(CONFIG_PREEMPT_RT)
+# define lockdep_softirq_enter()		\
+do {						\
+	current->softirq_context++;		\
+} while (0)
+# define lockdep_softirq_exit()			\
+do {						\
+	current->softirq_context--;		\
+} while (0)
+
+#else
+# define lockdep_softirq_enter()		do { } while (0)
+# define lockdep_softirq_exit()			do { } while (0)
+#endif
+
 #if defined(CONFIG_IRQSOFF_TRACER) || \
 	defined(CONFIG_PREEMPT_TRACER)
  extern void stop_critical_timings(void);
diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
index 1f00d46ffd4da..72816ee4fc65d 100644
--- a/kernel/locking/lockdep.c
+++ b/kernel/locking/lockdep.c
@@ -5471,6 +5471,7 @@ static noinstr void check_flags(unsigned long flags)
 		}
 	}
 
+#ifndef CONFIG_PREEMPT_RT
 	/*
 	 * We dont accurately track softirq state in e.g.
 	 * hardirq contexts (such as on 4KSTACKS), so only
@@ -5485,6 +5486,7 @@ static noinstr void check_flags(unsigned long flags)
 			DEBUG_LOCKS_WARN_ON(!current->softirqs_enabled);
 		}
 	}
+#endif
 
 	if (!debug_locks)
 		print_irqtrace_events(current);
-- 
2.55.0

