Commit 0c1d7a2c authored by Thomas Gleixner's avatar Thomas Gleixner Committed by Peter Zijlstra
Browse files

lockdep: Remove softirq accounting on PREEMPT_RT. 



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 a 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: default avatarThomas Gleixner <tglx@linutronix.de>
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20211129174654.668506-6-bigeasy@linutronix.de
parent a3642021

include/linux/irqflags.h

+15 −8
Original line number Diff line number Diff line
@@ -71,14 +71,6 @@ 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)		\

({							\
@@ -140,6 +132,21 @@ 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);

kernel/locking/lockdep.c

+2 −0
Original line number Diff line number Diff line
@@ -5485,6 +5485,7 @@ 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
@@ -5499,6 +5500,7 @@ static noinstr void check_flags(unsigned long flags) 
			DEBUG_LOCKS_WARN_ON(!current->softirqs_enabled);

		}

	}

#endif



	if (!debug_locks)

		print_irqtrace_events(current);