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#ifndef Py_CRITICAL_SECTION_H

#define Py_CRITICAL_SECTION_H

#ifdef __cplusplus

extern "C" {

#endif

// Python critical sections

// Conceptually, critical sections are a deadlock avoidance layer on top of

// per-object locks. These helpers, in combination with those locks, replace

// our usage of the global interpreter lock to provide thread-safety for

// otherwise thread-unsafe objects, such as dict.

// NOTE: These APIs are no-ops in non-free-threaded builds.

// NOTE: Only the top-most critical section is guaranteed to be active.

// Operations that need to lock two objects at once must use

// `Py_BEGIN_CRITICAL_SECTION2()`. You *CANNOT* use nested critical sections

// to lock more than one object at once, because the inner critical section

// may suspend the outer critical sections. This API does not provide a way

// to lock more than two objects at once (though it could be added later

// if actually needed).

// NOTE: Critical sections implicitly behave like reentrant locks because

// attempting to acquire the same lock will suspend any outer (earlier)

// critical sections. However, they are less efficient for this use case than

// purposefully designed reentrant locks.

// Example usage:

// Py_BEGIN_CRITICAL_SECTION(op);

// ...

// Py_END_CRITICAL_SECTION();

// To lock two objects at once:

// Py_BEGIN_CRITICAL_SECTION2(op1, op2);

// ...

// Py_END_CRITICAL_SECTION2();

// NOTE: the contents of this struct are private and their meaning may

// change betweeen Python releases without a deprecation period.

typedef struct PyCriticalSection {

// Tagged pointer to an outer active critical section (or 0).

uintptr_t _cs_prev;

// Mutex used to protect critical section

struct PyMutex *_cs_mutex;

} PyCriticalSection;

// A critical section protected by two mutexes. Use

// Py_BEGIN_CRITICAL_SECTION2 and Py_END_CRITICAL_SECTION2.

// NOTE: the contents of this struct are private and may change betweeen

// Python releases without a deprecation period.

typedef struct PyCriticalSection2 {

PyCriticalSection _cs_base;

struct PyMutex *_cs_mutex2;

} PyCriticalSection2;

PyAPI_FUNC(void)

PyCriticalSection_Begin(PyCriticalSection *c, PyObject *op);

PyAPI_FUNC(void)

PyCriticalSection_End(PyCriticalSection *c);

PyAPI_FUNC(void)

PyCriticalSection2_Begin(PyCriticalSection2 *c, PyObject *a, PyObject *b);

PyAPI_FUNC(void)

PyCriticalSection2_End(PyCriticalSection2 *c);

// These are definitions for the stable ABI. For GIL-ful builds they're

// conditionally redefined as no-ops in cpython/critical_section.h.

# define Py_BEGIN_CRITICAL_SECTION(op) \

{ \

PyCriticalSection _py_cs; \

PyCriticalSection_Begin(&_py_cs, _PyObject_CAST(op))

# define Py_END_CRITICAL_SECTION() \

PyCriticalSection_End(&_py_cs); \

}

# define Py_BEGIN_CRITICAL_SECTION2(a, b) \

{ \

PyCriticalSection2 _py_cs2; \

PyCriticalSection2_Begin(&_py_cs2, _PyObject_CAST(a), _PyObject_CAST(b))

# define Py_END_CRITICAL_SECTION2() \

PyCriticalSection2_End(&_py_cs2); \

}

#ifndef Py_LIMITED_API

# define Py_CPYTHON_CRITICAL_SECTION_H

# include "cpython/critical_section.h"

# undef Py_CPYTHON_CRITICAL_SECTION_H

#endif

#ifdef __cplusplus

}

#endif

#endif /* !Py_CRITICAL_SECTION_H */

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