mutex.c File Reference

A simple mutex in C. More...

Go to the source code of this file.

Functions
int	mutex_check (MUTEX *mutex_ptr)
	Checks whether a given mutex is locked.
void	mutex_lock (MUTEX *mutex_ptr)
	Locks a mutex.
void	mutex_unlock (MUTEX *mutex_ptr)
	Unlocks a mutex.

---

Detailed Description

A simple mutex in C.

Author:

Nicolas Williamson

Date:

January 2010

Definition in file mutex.c.

---

Function Documentation

int mutex_check

(

MUTEX *

mutex_ptr

)

Checks whether a given mutex is locked.

Non-blocking.

Parameters:

mutex_ptr

A pointer to the mutex.

Returns:

• 1: The mutex is locked.
• 0: The mutex is unlocked.

Definition at line 47 of file mutex.c.

Referenced by error_occurred(), error_occurred_fiq(), error_occurred_irq(), and mutex_lock().

                                 {
  return *mutex_ptr;
}

void mutex_lock

(

MUTEX *

mutex_ptr

)

Locks a mutex.

No other process which requires this mutex may run until the mutex is unlocked. This function will block and wait until the mutex it is trying to lock is free (no other process has a lock on it).

Parameters:

mutex_ptr

A pointer to the mutex.

Definition at line 25 of file mutex.c.

References mutex_check().

Referenced by error_occurred(), error_occurred_fiq(), and error_occurred_irq().

                                 {
  while (mutex_check(mutex_ptr)){} //block until mutex is unlocked
  *mutex_ptr = 1; //locked
}

void mutex_unlock

(

MUTEX *

mutex_ptr

)

Unlocks a mutex.

Once a process has finished executing its critical code, it should unlock the mutex to allow other processes to lock it.

Parameters:

mutex_ptr

A pointer to the mutex.

Definition at line 36 of file mutex.c.

Referenced by error_occurred(), error_occurred_fiq(), and error_occurred_irq().

                                   {
  *mutex_ptr = 0; //unlocked
}