05 Concurrency and Race Conditions .

//spinlock 
#include <linux/spinlock.h>
spinlock_t mylock = SPIN_LOCK_UNLOCKED; /* Initialize */

/* Acquire the spinlock. This is inexpensive if there
* is no one inside the critical section. In the face of
* contention, spinlock() has to busy-wait.
*/
spin_lock(&mylock);

/* ... Critical Section code ... */

spin_unlock(&mylock); /* Release the lock */

//Basic mutex usage is as follows:

#include <linux/mutex.h>

/* Statically declare a mutex. To dynamically
   create a mutex, use mutex_init() */
static DEFINE_MUTEX(mymutex);

/* Acquire the mutex. This is inexpensive if there
 * is no one inside the critical section. In the face of
 * contention, mutex_lock() puts the calling thread to sleep.
 */
mutex_lock(&mymutex);

/* ... Critical Section code ... */

mutex_unlock(&mymutex);      /* Release the mutex */


//Basic usage of the semaphore interface is as follows:

#include <asm/semaphore.h>  /* Architecture dependent
                               header */

/* Statically declare a semaphore. To dynamically
   create a semaphore, use init_MUTEX() */
static DECLARE_MUTEX(mysem);

down(&mysem);    /* Acquire the semaphore */

/* ... Critical Section code ... */

up(&mysem);      /* Release the semaphore */

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