spinlock.h File Reference

Simple locking. More...

#include <sys/cdefs.h>
#include <kos/thread.h>

Go to the source code of this file.

Macros
#define	SPINLOCK_INITIALIZER   0
	Spinlock initializer.
#define	spinlock_init(A)   *(A) = SPINLOCK_INITIALIZER
	Initialize a spinlock.
#define	spinlock_lock(A)
	Spin on a lock.
#define	spinlock_trylock(A)
	Try to lock, without spinning.
#define	spinlock_unlock(A)
	Free a lock.
#define	spinlock_is_locked(A)   ( *(A) != 0 )
	Determine if a lock is locked.

Typedefs
typedef volatile int	spinlock_t
	Spinlock data type.

Detailed Description

Simple locking.

This file contains definitions for very simple locks. Most of the time, you will probably not use such low-level locking, but will opt for something more fully featured like mutexes, semaphores, reader-writer semaphores, or recursive locks.

Author

Megan Potter

See also

kos/sem.h

kos/mutex.h

kos/rwsem.h

kos/recursive_lock.h

Macro Definition Documentation

spinlock_init

#define spinlock_init

(

A

)

*(A) = SPINLOCK_INITIALIZER

Initialize a spinlock.

This function-like macro abstracts initializing a spinlock, in case the initializer is not applicable to what you are doing.

Parameters

A	A pointer to the spinlock to be initialized.

SPINLOCK_INITIALIZER

#define SPINLOCK_INITIALIZER   0

Spinlock initializer.

All created spinlocks should be initialized with this initializer so that they are in a sane state, ready to be used.

spinlock_is_locked

#define spinlock_is_locked

(

A

)

( *(A) != 0 )

Determine if a lock is locked.

This macro will return whether or not the lock specified is actually locked when it is called. This is NOT a thread-safe way of determining if a lock will be locked when you get around to locking it!

Parameters

A	A pointer to the spinlock to be checked.

spinlock_lock

#define spinlock_lock

(

A

)

Value:

        do { \
        spinlock_t * __lock = A; \
        int __gotlock = 0; \
        while(1) { \
            __asm__ __volatile__("tas.b @%1\n\t" \
                                 "movt %0\n\t" \
                                 : "=r" (__gotlock) \
                                 : "r" (__lock) \
                                 : "t", "memory"); \
            if(!__gotlock) \
                thd_pass(); \
            else break; \
        } \
    } while(0)

Spin on a lock.

This macro will spin on the lock, and will not return until the lock has been obtained for the calling thread.

Parameters

A	A pointer to the spinlock to be locked.

spinlock_trylock

#define spinlock_trylock

(

A

)

Value:

        ({ \
        int __gotlock = 0; \
        do { \
            spinlock_t *__lock = A; \
            __asm__ __volatile__("tas.b @%1\n\t" \
                                 "movt %0\n\t" \
                                 : "=r" (__gotlock) \
                                 : "r" (__lock) \
                                 : "t", "memory"); \
        } while(0); \
        __gotlock; \
    })

Try to lock, without spinning.

This macro will attempt to lock the lock, but will not spin. Instead, it will return whether the lock was obtained or not.

Parameters

A	A pointer to the spinlock to be locked.

Returns

0 if the lock is held by another thread. Non-zero if the lock was successfully obtained.

spinlock_unlock

#define spinlock_unlock

(

A

)

Value:

        do { \
        *(A) = 0; \
    } while(0)

Free a lock.

This macro will unlock the lock that is currently held by the calling thread. Do not use this macro unless you actually hold the lock!

Parameters

A	A pointer to the spinlock to be unlocked.

Typedef Documentation

spinlock_t

typedef volatile int spinlock_t

Spinlock data type.