lockdep: Add posixtimer context tracing bits

Splitting run_posix_cpu_timers() into two parts is work in progress which
is stuck on other entry code related problems. The heavy lifting which
involves locking of sighand lock will be moved into task context so the
necessary execution time is burdened on the task and not on interrupt
context.

Until this work completes lockdep with the spinlock nesting rules enabled
would emit warnings for this known context.

Prevent it by setting "->irq_config = 1" for the invocation of
run_posix_cpu_timers() so lockdep does not complain when sighand lock is
acquried. This will be removed once the split is completed.

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/20200321113242.751182723@linutronix.de

diff --git a/include/linux/irqflags.h b/include/linux/irqflags.h
index f23f540e0ebbad9b8a352865345bdaf5de53d2cb..a16adbb58f66abd2d0690f0ca43cb98f6ca3049d 100644 (file)
--- a/include/linux/irqflags.h
+++ b/include/linux/irqflags.h
@@ -69,6 +69,16 @@ do {                                         \
                        current->irq_config = 0;        \
          } while (0)
 
+# define lockdep_posixtimer_enter()                            \
+         do {                                                  \
+                 current->irq_config = 1;                      \
+         } while (0)
+
+# define lockdep_posixtimer_exit()                             \
+         do {                                                  \
+                 current->irq_config = 0;                      \
+         } while (0)
+
 # define lockdep_irq_work_enter(__work)                                        \
          do {                                                          \
                  if (!(atomic_read(&__work->flags) & IRQ_WORK_HARD_IRQ))\
@@ -94,6 +104,8 @@ do {                                         \
 # define lockdep_softirq_exit()                do { } while (0)
 # define lockdep_hrtimer_enter(__hrtimer)              do { } while (0)
 # define lockdep_hrtimer_exit(__hrtimer)               do { } while (0)
+# define lockdep_posixtimer_enter()            do { } while (0)
+# define lockdep_posixtimer_exit()             do { } while (0)
 # define lockdep_irq_work_enter(__work)                do { } while (0)
 # define lockdep_irq_work_exit(__work)         do { } while (0)
 #endif

diff --git a/kernel/time/posix-cpu-timers.c b/kernel/time/posix-cpu-timers.c
index 8ff6da77a01fdef5b3aa6d9dc77075c492a0bb17..2c48a7233b1960d2593207741909bd4c13eba0d9 100644 (file)
--- a/kernel/time/posix-cpu-timers.c
+++ b/kernel/time/posix-cpu-timers.c
@@ -1126,8 +1126,11 @@ void run_posix_cpu_timers(void)
        if (!fastpath_timer_check(tsk))
                return;
 
-       if (!lock_task_sighand(tsk, &flags))
+       lockdep_posixtimer_enter();
+       if (!lock_task_sighand(tsk, &flags)) {
+               lockdep_posixtimer_exit();
                return;
+       }
        /*
         * Here we take off tsk->signal->cpu_timers[N] and
         * tsk->cpu_timers[N] all the timers that are firing, and
@@ -1169,6 +1172,7 @@ void run_posix_cpu_timers(void)
                        cpu_timer_fire(timer);
                spin_unlock(&timer->it_lock);
        }
+       lockdep_posixtimer_exit();
 }
 
 /*