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lockdep: Remove softirq accounting on PREEMPT_RT.

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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: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20211129174654.668506-6-bigeasy@linutronix.de
This commit is contained in:
Thomas Gleixner 2021-11-29 18:46:48 +01:00 committed by Peter Zijlstra
parent a364202192
commit 0c1d7a2c2d
2 changed files with 17 additions and 8 deletions
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23
include/linux/irqflags.h
View File

@ -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);

2
kernel/locking/lockdep.c
View File

@ -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);