forked from KolibriOS/kolibrios
87 lines
2.8 KiB
C
87 lines
2.8 KiB
C
/*
|
|
* Mutexes: blocking mutual exclusion locks
|
|
*
|
|
* started by Ingo Molnar:
|
|
*
|
|
* Copyright (C) 2004, 2005, 2006 Red Hat, Inc., Ingo Molnar <mingo@redhat.com>
|
|
*
|
|
* This file contains the main data structure and API definitions.
|
|
*/
|
|
#ifndef __LINUX_MUTEX_H
|
|
#define __LINUX_MUTEX_H
|
|
|
|
#include <linux/list.h>
|
|
#include <asm/atomic.h>
|
|
|
|
/*
|
|
* Simple, straightforward mutexes with strict semantics:
|
|
*
|
|
* - only one task can hold the mutex at a time
|
|
* - only the owner can unlock the mutex
|
|
* - multiple unlocks are not permitted
|
|
* - recursive locking is not permitted
|
|
* - a mutex object must be initialized via the API
|
|
* - a mutex object must not be initialized via memset or copying
|
|
* - task may not exit with mutex held
|
|
* - memory areas where held locks reside must not be freed
|
|
* - held mutexes must not be reinitialized
|
|
* - mutexes may not be used in hardware or software interrupt
|
|
* contexts such as tasklets and timers
|
|
*
|
|
* These semantics are fully enforced when DEBUG_MUTEXES is
|
|
* enabled. Furthermore, besides enforcing the above rules, the mutex
|
|
* debugging code also implements a number of additional features
|
|
* that make lock debugging easier and faster:
|
|
*
|
|
* - uses symbolic names of mutexes, whenever they are printed in debug output
|
|
* - point-of-acquire tracking, symbolic lookup of function names
|
|
* - list of all locks held in the system, printout of them
|
|
* - owner tracking
|
|
* - detects self-recursing locks and prints out all relevant info
|
|
* - detects multi-task circular deadlocks and prints out all affected
|
|
* locks and tasks (and only those tasks)
|
|
*/
|
|
struct mutex {
|
|
/* 1: unlocked, 0: locked, negative: locked, possible waiters */
|
|
struct list_head wait_list;
|
|
atomic_t count;
|
|
};
|
|
|
|
/*
|
|
* This is the control structure for tasks blocked on mutex,
|
|
* which resides on the blocked task's kernel stack:
|
|
*/
|
|
struct mutex_waiter {
|
|
struct list_head list;
|
|
int *task;
|
|
};
|
|
|
|
|
|
#define __MUTEX_INITIALIZER(lockname) \
|
|
{ .wait_list = LIST_HEAD_INIT(lockname.wait_list), \
|
|
.count = ATOMIC_INIT(1) \
|
|
}
|
|
|
|
#define DEFINE_MUTEX(mutexname) \
|
|
struct mutex mutexname = __MUTEX_INITIALIZER(mutexname)
|
|
|
|
void __attribute__ ((fastcall)) __attribute__ ((dllimport))
|
|
mutex_init(struct mutex*)__asm__("MutexInit");
|
|
void __attribute__ ((fastcall)) __attribute__ ((dllimport))
|
|
mutex_lock(struct mutex*)__asm__("MutexLock");
|
|
void __attribute__ ((fastcall)) __attribute__ ((dllimport))
|
|
mutex_unlock(struct mutex*)__asm__("MutexUnlock");
|
|
|
|
/**
|
|
* mutex_is_locked - is the mutex locked
|
|
* @lock: the mutex to be queried
|
|
*
|
|
* Returns 1 if the mutex is locked, 0 if unlocked.
|
|
*/
|
|
static inline int mutex_is_locked(struct mutex *lock)
|
|
{
|
|
return atomic_read(&lock->count) != 1;
|
|
}
|
|
|
|
#endif
|