linux-kernel - [PATCH 7/9] lockdep: Add hrtimer context tracing bits

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Message-Id: <20200313174701.148376-8-bigeasy@linutronix.de>
Date:   Fri, 13 Mar 2020 18:46:59 +0100
From:   Sebastian Andrzej Siewior <bigeasy@...utronix.de>
To:     linux-kernel@...r.kernel.org
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...nel.org>, Will Deacon <will@...nel.org>,
        "Paul E . McKenney" <paulmck@...nel.org>,
        Joel Fernandes <joel@...lfernandes.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Sebastian Andrzej Siewior <bigeasy@...utronix.de>
Subject: [PATCH 7/9] lockdep: Add hrtimer context tracing bits

Set current->irq_config = 1 for hrtimers which are not marked to expire in
hard interrupt context during hrtimer_init(). These timers will expire in
softirq context on PREEMPT_RT.

Setting this allows lockdep to differentiate these timers. If a timer is
marked to expire in hard interrupt context then the timer callback is not
supposed to acquire a regular spinlock instead of a raw_spinlock in the
expiry callback.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
---
 include/linux/irqflags.h | 15 +++++++++++++++
 include/linux/sched.h    |  1 +
 kernel/locking/lockdep.c |  2 +-
 kernel/time/hrtimer.c    |  6 +++++-
 4 files changed, 22 insertions(+), 2 deletions(-)

diff --git a/include/linux/irqflags.h b/include/linux/irqflags.h
index fdaf28601cbe1..9c17f9c827aac 100644
--- a/include/linux/irqflags.h
+++ b/include/linux/irqflags.h
@@ -56,6 +56,19 @@ do {						\
 do {						\
 	current->softirq_context--;		\
 } while (0)
+
+# define lockdep_hrtimer_enter(__hrtimer)		\
+	  do {						\
+		  if (!__hrtimer->is_hard)		\
+			current->irq_config = 1;	\
+	  } while (0)
+
+# define lockdep_hrtimer_exit(__hrtimer)		\
+	  do {						\
+		  if (!__hrtimer->is_hard)		\
+			current->irq_config = 0;	\
+	  } while (0)
+
 #else
 # define trace_hardirqs_on()		do { } while (0)
 # define trace_hardirqs_off()		do { } while (0)
@@ -68,6 +81,8 @@ do {						\
 # define trace_hardirq_exit()		do { } while (0)
 # define lockdep_softirq_enter()	do { } while (0)
 # define lockdep_softirq_exit()		do { } while (0)
+# define lockdep_hrtimer_enter(__hrtimer)		do { } while (0)
+# define lockdep_hrtimer_exit(__hrtimer)		do { } while (0)
 #endif
 
 #if defined(CONFIG_IRQSOFF_TRACER) || \
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 4d3b9ecce0742..933914cdf2197 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -983,6 +983,7 @@ struct task_struct {
 	unsigned int			softirq_enable_event;
 	int				softirqs_enabled;
 	int				softirq_context;
+	int				irq_config;
 #endif
 
 #ifdef CONFIG_LOCKDEP
diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
index 4a9abf8bd9d15..df74531fd9f85 100644
--- a/kernel/locking/lockdep.c
+++ b/kernel/locking/lockdep.c
@@ -3879,7 +3879,7 @@ static int check_wait_context(struct task_struct *curr, struct held_lock *next)
 		/*
 		 * Check if force_irqthreads will run us threaded.
 		 */
-		if (curr->hardirq_threaded)
+		if (curr->hardirq_threaded || curr->irq_config)
 			curr_inner = LD_WAIT_CONFIG;
 		else
 			curr_inner = LD_WAIT_SPIN;
diff --git a/kernel/time/hrtimer.c b/kernel/time/hrtimer.c
index 3a609e7344f3d..8cce72501aea5 100644
--- a/kernel/time/hrtimer.c
+++ b/kernel/time/hrtimer.c
@@ -1404,7 +1404,7 @@ static void __hrtimer_init(struct hrtimer *timer, clockid_t clock_id,
 	base = softtimer ? HRTIMER_MAX_CLOCK_BASES / 2 : 0;
 	base += hrtimer_clockid_to_base(clock_id);
 	timer->is_soft = softtimer;
-	timer->is_hard = !softtimer;
+	timer->is_hard = !!(mode & HRTIMER_MODE_HARD);
 	timer->base = &cpu_base->clock_base[base];
 	timerqueue_init(&timer->node);
 }
@@ -1514,7 +1514,11 @@ static void __run_hrtimer(struct hrtimer_cpu_base *cpu_base,
 	 */
 	raw_spin_unlock_irqrestore(&cpu_base->lock, flags);
 	trace_hrtimer_expire_entry(timer, now);
+	lockdep_hrtimer_enter(timer);
+
 	restart = fn(timer);
+
+	lockdep_hrtimer_exit(timer);
 	trace_hrtimer_expire_exit(timer);
 	raw_spin_lock_irq(&cpu_base->lock);
 
-- 
2.25.1