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From: Thomas Gleixner <tglx@linutronix.de>
Date: Mon, 29 Nov 2021 18:46:48 +0100
Subject: [PATCH 05/11] 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: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Link: https://lore.kernel.org/r/20211129174654.668506-6-bigeasy@linutronix.de
---
include/linux/irqflags.h | 23 +++++++++++++++--------
kernel/locking/lockdep.c | 2 ++
2 files changed, 17 insertions(+), 8 deletions(-)
--- a/include/linux/irqflags.h
+++ b/include/linux/irqflags.h
@@ -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);
--- a/kernel/locking/lockdep.c
+++ b/kernel/locking/lockdep.c
@@ -5485,6 +5485,7 @@ static noinstr void check_flags(unsigned
}
}
+#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
DEBUG_LOCKS_WARN_ON(!current->softirqs_enabled);
}
}
+#endif
if (!debug_locks)
print_irqtrace_events(current);
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