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kernel/include/linux/irqflags.h
Mark Rutland 997acaf6b4 lockdep: report broken irq restoration 
We generally expect local_irq_save() and local_irq_restore() to be
paired and sanely nested, and so local_irq_restore() expects to be
called with irqs disabled. Thus, within local_irq_restore() we only
trace irq flag changes when unmasking irqs.

This means that a sequence such as:

| local_irq_disable();
| local_irq_save(flags);
| local_irq_enable();
| local_irq_restore(flags);

... is liable to break things, as the local_irq_restore() would mask
irqs without tracing this change. Similar problems may exist for
architectures whose arch_irq_restore() function depends on being called
with irqs disabled.

We don't consider such sequences to be a good idea, so let's define
those as forbidden, and add tooling to detect such broken cases.

This patch adds debug code to WARN() when raw_local_irq_restore() is
called with irqs enabled. As raw_local_irq_restore() is expected to pair
with raw_local_irq_save(), it should never be called with irqs enabled.

To avoid the possibility of circular header dependencies between
irqflags.h and bug.h, the warning is handled in a separate C file.

The new code is all conditional on a new CONFIG_DEBUG_IRQFLAGS symbol
which is independent of CONFIG_TRACE_IRQFLAGS. As noted above such cases
will confuse lockdep, so CONFIG_DEBUG_LOCKDEP now selects
CONFIG_DEBUG_IRQFLAGS.

Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20210111153707.10071-1-mark.rutland@arm.com
2021-01-22 11:08:56 +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>
#include <asm/percpu.h>
/* Currently lockdep_softirqs_on/off is used only by lockdep */
#ifdef CONFIG_PROVE_LOCKING
extern void lockdep_softirqs_on(unsigned long ip);
extern void lockdep_softirqs_off(unsigned long ip);
extern void lockdep_hardirqs_on_prepare(unsigned long ip);
extern void lockdep_hardirqs_on(unsigned long ip);
extern void lockdep_hardirqs_off(unsigned long ip);
#else
static inline void lockdep_softirqs_on(unsigned long ip) { }
static inline void lockdep_softirqs_off(unsigned long ip) { }
static inline void lockdep_hardirqs_on_prepare(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
/* Per-task IRQ trace events information. */
struct irqtrace_events {
unsigned int irq_events;
unsigned long hardirq_enable_ip;
unsigned long hardirq_disable_ip;
unsigned int hardirq_enable_event;
unsigned int hardirq_disable_event;
unsigned long softirq_disable_ip;
unsigned long softirq_enable_ip;
unsigned int softirq_disable_event;
unsigned int softirq_enable_event;
};
DECLARE_PER_CPU(int, hardirqs_enabled);
DECLARE_PER_CPU(int, hardirq_context);
extern void trace_hardirqs_on_prepare(void);
extern void trace_hardirqs_off_finish(void);
extern void trace_hardirqs_on(void);
extern void trace_hardirqs_off(void);
# define lockdep_hardirq_context() (raw_cpu_read(hardirq_context))
# define lockdep_softirq_context(p) ((p)->softirq_context)
# define lockdep_hardirqs_enabled() (this_cpu_read(hardirqs_enabled))
# define lockdep_softirqs_enabled(p) ((p)->softirqs_enabled)
# define lockdep_hardirq_enter() \
do { \
if (__this_cpu_inc_return(hardirq_context) == 1)\
current->hardirq_threaded = 0; \
} while (0)
# define lockdep_hardirq_threaded() \
do { \
current->hardirq_threaded = 1; \
} while (0)
# define lockdep_hardirq_exit() \
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) \
({ \
bool __expires_hardirq = true; \
\
if (!__hrtimer->is_hard) { \
current->irq_config = 1; \
__expires_hardirq = false; \
} \
__expires_hardirq; \
})
# define lockdep_hrtimer_exit(__expires_hardirq) \
do { \
if (!__expires_hardirq) \
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(_flags) \
do { \
if (!((_flags) & IRQ_WORK_HARD_IRQ)) \
current->irq_config = 1; \
} while (0)
# define lockdep_irq_work_exit(_flags) \
do { \
if (!((_flags) & IRQ_WORK_HARD_IRQ)) \
current->irq_config = 0; \
} while (0)
#else
# define trace_hardirqs_on_prepare() do { } while (0)
# define trace_hardirqs_off_finish() do { } while (0)
# define trace_hardirqs_on() do { } while (0)
# define trace_hardirqs_off() do { } while (0)
# define lockdep_hardirq_context() 0
# define lockdep_softirq_context(p) 0
# define lockdep_hardirqs_enabled() 0
# define lockdep_softirqs_enabled(p) 0
# define lockdep_hardirq_enter() do { } while (0)
# define lockdep_hardirq_threaded() do { } while (0)
# define lockdep_hardirq_exit() do { } while (0)
# define lockdep_softirq_enter() do { } while (0)
# define lockdep_softirq_exit() do { } while (0)
# define lockdep_hrtimer_enter(__hrtimer) false
# define lockdep_hrtimer_exit(__context) 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
#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
#ifdef CONFIG_DEBUG_IRQFLAGS
extern void warn_bogus_irq_restore(void);
#define raw_check_bogus_irq_restore() \
do { \
if (unlikely(!arch_irqs_disabled())) \
warn_bogus_irq_restore(); \
} while (0)
#else
#define raw_check_bogus_irq_restore() 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); \
raw_check_bogus_irq_restore(); \
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 { \
bool was_disabled = raw_irqs_disabled();\
raw_local_irq_disable(); \
if (!was_disabled) \
trace_hardirqs_off(); \
} while (0)
#define local_irq_save(flags) \
do { \
raw_local_irq_save(flags); \
if (!raw_irqs_disabled_flags(flags)) \
trace_hardirqs_off(); \
} while (0)
#define local_irq_restore(flags) \
do { \
if (!raw_irqs_disabled_flags(flags)) \
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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