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linux-stable/include/linux/irqflags.h
Peter Zijlstra de8f5e4f2d lockdep: Introduce wait-type checks 
Extend lockdep to validate lock wait-type context.

The current wait-types are:

	LD_WAIT_FREE,		/* wait free, rcu etc.. */
	LD_WAIT_SPIN,		/* spin loops, raw_spinlock_t etc.. */
	LD_WAIT_CONFIG,		/* CONFIG_PREEMPT_LOCK, spinlock_t etc.. */
	LD_WAIT_SLEEP,		/* sleeping locks, mutex_t etc.. */

Where lockdep validates that the current lock (the one being acquired)
fits in the current wait-context (as generated by the held stack).

This ensures that there is no attempt to acquire mutexes while holding
spinlocks, to acquire spinlocks while holding raw_spinlocks and so on. In
other words, its a more fancy might_sleep().

Obviously RCU made the entire ordeal more complex than a simple single
value test because RCU can be acquired in (pretty much) any context and
while it presents a context to nested locks it is not the same as it
got acquired in.

Therefore its necessary to split the wait_type into two values, one
representing the acquire (outer) and one representing the nested context
(inner). For most 'normal' locks these two are the same.

[ To make static initialization easier we have the rule that:
  .outer == INV means .outer == .inner; because INV == 0. ]

It further means that its required to find the minimal .inner of the held
stack to compare against the outer of the new lock; because while 'normal'
RCU presents a CONFIG type to nested locks, if it is taken while already
holding a SPIN type it obviously doesn't relax the rules.

Below is an example output generated by the trivial test code:

  raw_spin_lock(&foo);
  spin_lock(&bar);
  spin_unlock(&bar);
  raw_spin_unlock(&foo);

 [ BUG: Invalid wait context ]
 -----------------------------
 swapper/0/1 is trying to lock:
 ffffc90000013f20 (&bar){....}-{3:3}, at: kernel_init+0xdb/0x187
 other info that might help us debug this:
 1 lock held by swapper/0/1:
  #0: ffffc90000013ee0 (&foo){+.+.}-{2:2}, at: kernel_init+0xd1/0x187

The way to read it is to look at the new -{n,m} part in the lock
description; -{3:3} for the attempted lock, and try and match that up to
the held locks, which in this case is the one: -{2,2}.

This tells that the acquiring lock requires a more relaxed environment than
presented by the lock stack.

Currently only the normal locks and RCU are converted, the rest of the
lockdep users defaults to .inner = INV which is ignored. More conversions
can be done when desired.

The check for spinlock_t nesting is not enabled by default. It's a separate
config option for now as there are known problems which are currently
addressed. The config option allows to identify these problems and to
verify that the solutions found are indeed solving them.

The config switch will be removed and the checks will permanently enabled
once the vast majority of issues has been addressed.

[ bigeasy: Move LD_WAIT_FREE,… out of CONFIG_LOCKDEP to avoid compile
	   failure with CONFIG_DEBUG_SPINLOCK + !CONFIG_LOCKDEP]
[ tglx: Add the config option ]

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
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/20200321113242.427089655@linutronix.de
2020-03-21 16:00:24 +01:00

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/* SPDX-License-Identifier: GPL-2.0 */
/*
* include/linux/irqflags.h
*
* IRQ flags tracing: follow the state of the hardirq and softirq flags and
* provide callbacks for transitions between ON and OFF states.
*
* This file gets included from lowlevel asm headers too, to provide
* wrapped versions of the local_irq_*() APIs, based on the
* raw_local_irq_*() macros from the lowlevel headers.
*/
#ifndef _LINUX_TRACE_IRQFLAGS_H
#define _LINUX_TRACE_IRQFLAGS_H
#include <linux/typecheck.h>
#include <asm/irqflags.h>
/* Currently trace_softirqs_on/off is used only by lockdep */
#ifdef CONFIG_PROVE_LOCKING
extern void trace_softirqs_on(unsigned long ip);
extern void trace_softirqs_off(unsigned long ip);
extern void lockdep_hardirqs_on(unsigned long ip);
extern void lockdep_hardirqs_off(unsigned long ip);
#else
static inline void trace_softirqs_on(unsigned long ip) { }
static inline void trace_softirqs_off(unsigned long ip) { }
static inline void lockdep_hardirqs_on(unsigned long ip) { }
static inline void lockdep_hardirqs_off(unsigned long ip) { }
#endif
#ifdef CONFIG_TRACE_IRQFLAGS
extern void trace_hardirqs_on(void);
extern void trace_hardirqs_off(void);
# define trace_hardirq_context(p) ((p)->hardirq_context)
# define trace_softirq_context(p) ((p)->softirq_context)
# define trace_hardirqs_enabled(p) ((p)->hardirqs_enabled)
# define trace_softirqs_enabled(p) ((p)->softirqs_enabled)
# define trace_hardirq_enter() \
do { \
if (!current->hardirq_context++) \
current->hardirq_threaded = 0; \
} while (0)
# define trace_hardirq_threaded() \
do { \
current->hardirq_threaded = 1; \
} while (0)
# define trace_hardirq_exit() \
do { \
current->hardirq_context--; \
} while (0)
# define lockdep_softirq_enter() \
do { \
current->softirq_context++; \
} while (0)
# define lockdep_softirq_exit() \
do { \
current->softirq_context--; \
} while (0)
#else
# define trace_hardirqs_on() do { } while (0)
# define trace_hardirqs_off() do { } while (0)
# define trace_hardirq_context(p) 0
# define trace_softirq_context(p) 0
# define trace_hardirqs_enabled(p) 0
# define trace_softirqs_enabled(p) 0
# define trace_hardirq_enter() do { } while (0)
# define trace_hardirq_threaded() do { } while (0)
# define trace_hardirq_exit() do { } while (0)
# 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);
extern void start_critical_timings(void);
#else
# define stop_critical_timings() do { } while (0)
# define start_critical_timings() do { } while (0)
#endif
/*
* Wrap the arch provided IRQ routines to provide appropriate checks.
*/
#define raw_local_irq_disable() arch_local_irq_disable()
#define raw_local_irq_enable() arch_local_irq_enable()
#define raw_local_irq_save(flags) \
do { \
typecheck(unsigned long, flags); \
flags = arch_local_irq_save(); \
} while (0)
#define raw_local_irq_restore(flags) \
do { \
typecheck(unsigned long, flags); \
arch_local_irq_restore(flags); \
} while (0)
#define raw_local_save_flags(flags) \
do { \
typecheck(unsigned long, flags); \
flags = arch_local_save_flags(); \
} while (0)
#define raw_irqs_disabled_flags(flags) \
({ \
typecheck(unsigned long, flags); \
arch_irqs_disabled_flags(flags); \
})
#define raw_irqs_disabled() (arch_irqs_disabled())
#define raw_safe_halt() arch_safe_halt()
/*
* The local_irq_*() APIs are equal to the raw_local_irq*()
* if !TRACE_IRQFLAGS.
*/
#ifdef CONFIG_TRACE_IRQFLAGS
#define local_irq_enable() \
do { trace_hardirqs_on(); raw_local_irq_enable(); } while (0)
#define local_irq_disable() \
do { raw_local_irq_disable(); trace_hardirqs_off(); } while (0)
#define local_irq_save(flags) \
do { \
raw_local_irq_save(flags); \
trace_hardirqs_off(); \
} while (0)
#define local_irq_restore(flags) \
do { \
if (raw_irqs_disabled_flags(flags)) { \
raw_local_irq_restore(flags); \
trace_hardirqs_off(); \
} else { \
trace_hardirqs_on(); \
raw_local_irq_restore(flags); \
} \
} while (0)
#define safe_halt() \
do { \
trace_hardirqs_on(); \
raw_safe_halt(); \
} while (0)
#else /* !CONFIG_TRACE_IRQFLAGS */
#define local_irq_enable() do { raw_local_irq_enable(); } while (0)
#define local_irq_disable() do { raw_local_irq_disable(); } while (0)
#define local_irq_save(flags) \
do { \
raw_local_irq_save(flags); \
} while (0)
#define local_irq_restore(flags) do { raw_local_irq_restore(flags); } while (0)
#define safe_halt() do { raw_safe_halt(); } while (0)
#endif /* CONFIG_TRACE_IRQFLAGS */
#define local_save_flags(flags) raw_local_save_flags(flags)
/*
* Some architectures don't define arch_irqs_disabled(), so even if either
* definition would be fine we need to use different ones for the time being
* to avoid build issues.
*/
#ifdef CONFIG_TRACE_IRQFLAGS_SUPPORT
#define irqs_disabled() \
({ \
unsigned long _flags; \
raw_local_save_flags(_flags); \
raw_irqs_disabled_flags(_flags); \
})
#else /* !CONFIG_TRACE_IRQFLAGS_SUPPORT */
#define irqs_disabled() raw_irqs_disabled()
#endif /* CONFIG_TRACE_IRQFLAGS_SUPPORT */
#define irqs_disabled_flags(flags) raw_irqs_disabled_flags(flags)
#endif
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