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@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20200321113242.534508206@linutronix.de

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) || \

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

kernel/locking/lockdep.c

@@ -4025,7 +4025,7 @@ 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;

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);