spinlock.h File Reference

Spin Locks. More...

#include <pthread.h>
#include "asterisk/compiler.h"

Include dependency graph for spinlock.h:

Go to the source code of this file.

Macros
#define	AST_SPINLOCK_TYPE   AST_SPINLOCK_TYPE_PTHREAD_MUTEX
	Implementation using GCC Atomics. More...
#define	AST_SPINLOCK_TYPE_LABEL   "pthread_mutex"

Typedefs
typedef pthread_mutex_t	ast_spinlock_t

Enumerations
enum	ast_spinlock_type {   AST_SPINLOCK_TYPE_GCC_ATOMICS, AST_SPINLOCK_TYPE_GAS_X86, AST_SPINLOCK_TYPE_GAS_ARM, AST_SPINLOCK_TYPE_GAS_SPARC,   AST_SPINLOCK_TYPE_OSX_ATOMICS, AST_SPINLOCK_TYPE_PTHREAD_SPINLOCK, AST_SPINLOCK_TYPE_PTHREAD_MUTEX }
	Spinlock Implementation Types. More...

Functions
static force_inline int	ast_spinlock_destroy (ast_spinlock_t *lock)
	Destroy a spin lock. More...
static force_inline int	ast_spinlock_init (ast_spinlock_t *lock)
	Initialize a spin lock. More...
static force_inline int	ast_spinlock_lock (ast_spinlock_t *lock)
	Lock a spin lock. More...
static force_inline int	ast_spinlock_trylock (ast_spinlock_t *lock)
	Try to lock a spin lock. More...
static force_inline int	ast_spinlock_unlock (ast_spinlock_t *lock)
	Unlock a spin lock. More...

Detailed Description

Spin Locks.

In some atomic operation circumstances the __atomic calls are not quite flexible enough but a full fledged mutex or rwlock is too expensive.

Spin locks should be used only for protecting short blocks of critical code such as simple compares and assignments. Operations that may block, hold a lock, or cause the thread to give up it's timeslice should NEVER be attempted in a spin lock.

Because spinlocks must be as lightweight as possible, there are no recursion or deadlock checks.

Definition in file spinlock.h.

Macro Definition Documentation

AST_SPINLOCK_TYPE

#define AST_SPINLOCK_TYPE   AST_SPINLOCK_TYPE_PTHREAD_MUTEX

Implementation using GCC Atomics.

Specifically, __sync_lock_test_and_set is used to atomically set/unset the lock variable.

Most recent gcc implementations support this method and it's performance is equal to or better than the assembly implementations hence it is the most preferred implementation on all platforms.

Implementation using x86 Assembly

For x86 implementations that don't support gcc atomics, this is the next best method.

Implementation using ARM Assembly

For ARM implementations that don't support gcc atomics, this is the next best method.

Implementation using Sparc Assembly

For Sparc implementations that don't support gcc atomics, this is the next best method.

Implementation using pthread_spinlock

pthread_spinlocks are not supported on all platforms but if for some reason none of the previous implementations are available, it can be used with reasonable performance.

Implementation using OSX Atomics

The Darwin/Mac OSX platform has its own atomics implementation but it uses more kernel time than GCC atomics and x86 assembly. It is included as an unlikely fallback.

Implementation using pthread_mutex

pthread_mutex is supported on all platforms but it is also the worst performing. It is included as an unlikely fallback.

Definition at line 405 of file spinlock.h.

AST_SPINLOCK_TYPE_LABEL

#define AST_SPINLOCK_TYPE_LABEL   "pthread_mutex"

Definition at line 406 of file spinlock.h.

Typedef Documentation

ast_spinlock_t

typedef pthread_mutex_t ast_spinlock_t

Definition at line 407 of file spinlock.h.

Enumeration Type Documentation

ast_spinlock_type

enum ast_spinlock_type

Spinlock Implementation Types.

Not all implementations will be available on all platforms.

Enumerator
AST_SPINLOCK_TYPE_GCC_ATOMICS
AST_SPINLOCK_TYPE_GAS_X86
AST_SPINLOCK_TYPE_GAS_ARM
AST_SPINLOCK_TYPE_GAS_SPARC
AST_SPINLOCK_TYPE_OSX_ATOMICS
AST_SPINLOCK_TYPE_PTHREAD_SPINLOCK
AST_SPINLOCK_TYPE_PTHREAD_MUTEX

Definition at line 47 of file spinlock.h.

                       {
   AST_SPINLOCK_TYPE_GCC_ATOMICS,
   AST_SPINLOCK_TYPE_GAS_X86,
   AST_SPINLOCK_TYPE_GAS_ARM,
   AST_SPINLOCK_TYPE_GAS_SPARC,
   AST_SPINLOCK_TYPE_OSX_ATOMICS,
   AST_SPINLOCK_TYPE_PTHREAD_SPINLOCK,
   AST_SPINLOCK_TYPE_PTHREAD_MUTEX,
};

Function Documentation

ast_spinlock_destroy()

static force_inline int ast_spinlock_destroy ( ast_spinlock_t *  lock )

static

Destroy a spin lock.

Parameters

lock	Address of the lock

Return values

0	Success
other	Failure

Definition at line 430 of file spinlock.h.

References ast_spinlock_init(), ast_spinlock_lock(), ast_spinlock_trylock(), ast_spinlock_unlock(), force_inline, lock, and pthread_mutex_destroy.

{
   return pthread_mutex_destroy(lock);
}

ast_spinlock_init()

static force_inline int ast_spinlock_init ( ast_spinlock_t *  lock )

static

Initialize a spin lock.

Parameters

lock	Address of the lock

Return values

0	Success
other	Failure

Definition at line 409 of file spinlock.h.

References NULL, and pthread_mutex_init.

Referenced by ast_spinlock_destroy().

{
   pthread_mutex_init(lock, NULL);
   return 0;
}

ast_spinlock_lock()

static force_inline int ast_spinlock_lock ( ast_spinlock_t *  lock )

static

Lock a spin lock.

Parameters

lock	Address of the lock

Return values

0	Success
other	Failure

Definition at line 415 of file spinlock.h.

References pthread_mutex_lock.

Referenced by ast_spinlock_destroy().

{
   return pthread_mutex_lock(lock);
}

ast_spinlock_trylock()

static force_inline int ast_spinlock_trylock ( ast_spinlock_t *  lock )

static

Try to lock a spin lock.

Attempt to gain a lock. Return immediately regardless of result.

Parameters

lock	Address of the lock

Return values

0	Success
other	Lock was not obtained

Definition at line 420 of file spinlock.h.

References pthread_mutex_trylock.

Referenced by ast_spinlock_destroy().

{
   return pthread_mutex_trylock(lock);
}

ast_spinlock_unlock()

static force_inline int ast_spinlock_unlock ( ast_spinlock_t *  lock )

static

Unlock a spin lock.

Parameters

lock	Address of the lock

Return values

0	Success
other	Failure

Definition at line 425 of file spinlock.h.

References pthread_mutex_unlock.

Referenced by ast_spinlock_destroy().

{
   return pthread_mutex_unlock(lock);
}