[patch V3 18/20] lockdep: Add hrtimer context tracing bits

Thomas Gleixner
2020-03-21T11:36:24Z

From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>

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>
---
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(-)

--- 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) || \
--- 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
--- a/kernel/locking/lockdep.c
+++ b/kernel/locking/lockdep.c
@@ -3759,7 +3759,7 @@ static int check_wait_context(struct tas
/*
* 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;
--- a/kernel/time/hrtimer.c
+++ b/kernel/time/hrtimer.c
@@ -1404,7 +1404,7 @@ static void __hrtimer_init(struct hrtime
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
*/
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);