source: CIVL/text/include/pthread.cvh@ 1a54e12

/*
  All specification references correspond to pages in the Standard for Information Technology
Portable Operating System Interface (POSIX)IEEE Computer Society Base Specifications, Issue 7.

Standard modifications to each translation:
header files are altered
errors are changed to assertion violations with appropriate messages
appropriate definitions are changed to input variables
*/

#include <civlc.h>
#include <stdio.h>
#include <stdlib.h>
#include <assert.h>
#include <stdbool.h>

//Mutex types
enum{
PTHREAD_MUTEX_NORMAL,
PTHREAD_MUTEX_RECURSIVE,
PTHREAD_MUTEX_ERRORCHECK
};

enum{
PTHREAD_MUTEX_STALLED,
PTHREAD_MUTEX_ROBUST
};

enum{
PTHREAD_CREATE_DETACHED,
PTHREAD_CREATE_JOINABLE
};

enum{
PTHREAD_SCOPE_SYSTEM,
PTHREAD_SCOPE_PROCESS
};

enum{
PTHREAD_INHERIT_SCHED,
PTHREAD_EXPLICIT_SCHED
};

//Mutex initializer
#define __LOCK_INITIALIZER      0
#define PTHREAD_MUTEX_INITIALIZER       {0,0,0,PTHREAD_MUTEX_NORMAL,__LOCK_INITIALIZER}
#define PTHREAD_COND_INITIALIZER        {__LOCK_INITIALIZER,0}

//Error definitions
enum{
EINVAL,      //Designates an invalid value
ENOTSUP,
EOWNERDEAD,  //Designates the termination of the owning thread
EBUSY,        //Mutex is already locked
EDEADLK,      //If mutex type is errorcheck and already owns the mutex
EPERM        //If mutex is robust or errorcheck and does not own the mutex
};

extern void *value = NULL;


/* Struct definitions */

/* pthread_attr_t struct definition
  Description: This struct corresponds to the pthread_attr_t which is the attribute of a pthread_t. It's fields
  define the way the pthread_t is able to interact (join/detach), (memory capacity), (scope) etc.
  
  Fields: void * stackaddr: The address of the attr's stack in memory
  size_t stacksize: The memory capacity for the attr's stack
  size_t guardsize: The guardsize attribute controls the size of the guard area for the created thread' stack. The
                    guardsize attribute provides protection against overflow of the stack pointer.
  int detachstate: Defines a threads ability to join with two values: PTHREAD_CREATE_DETACHED and PTHREAD_CREATE_JOINABLE
  int inheritsched: The inheritance scheduling policy of the thread
  int contentionscope: Defines the contention scope of the thread
  int schedpolicy: Determines the scheduling policy of the thread
  
*/

typedef struct {
  void *stackaddr;
  size_t stacksize;
  size_t guardsize;
  int detachstate;
  int inheritsched;
  int contentionscope;
  int schedpolicy;
} pthread_attr_t;

/* pthread_mutexattr_t struct definition
  Description: The pthread_mutexattr_t defines multiple attributes of a mutex and controls its interactions with threads 
  Fields: robust: defines the robustness of the mutex; if robust and the owning thread terminates, it will notify the 
          next thread of this to prevent deadlocks and other errors
          pshared: defines the process shared element of the thread and which processes can interact with the mutex
          protocol: defines the priority protocol of the mutex and which threads may interact first
          type: defines the type of the mutex as either PTHREAD_MUTEX_DEFAULT/NORMAL, PTHREAD_MUTEX_ERRORCHECK, or 
          PTHREAD_MUTEX_RECURSIVE, each explained in pthread_mutex_lock below
          prioceiling: defines the lowest priority the mutex's critical section can be at
*/

typedef struct {
  int robust;
  int pshared;
  int protocol;
  int type;
  int prioceiling;
}pthread_mutexattr_t;

/* pthread_mutex_t struct definition
  Description: The pthread_mutex_t is a locking mechanism for threads to interact with in order to control the scheduling
  of the threads. It can be locked, which allows for blocking of other threads waiting on the mutex and unlocked, allowing
  access. It has a pthread_mutexattr_t which defines its behavior.
  Fields: count - used for recursive mutex, incremented when locked, decremented when unlocked, mutex released when count is 0
  owner - current process owner of the mutex
  lock - int of 0 or 1, respectively 0 if unlocked, 1 if locked
  prioceiling - allows locking without adherence to the priority ceiling
  attr - see above
*/

typedef struct {
  int count;
  $proc owner;
  int lock;
  int prioceiling;
  pthread_mutexattr_t *attr;
} pthread_mutex_t;

//Unimplemented
/*
typedef struct {
  int pshared;
  clockid_t clock_id;
}pthread_condattr_t;
*/

/* pthread_cond_t struct definition
  Description: The pthread_cond_t is another locking mechanism which interacts with the mutex variable. When
  the mutex is locked, the condition can be accessed, leading the accessing thread to unlock it, and sleep
  until the signal is given
  Fields: proccount - specifies the number of processes/threads still waiting on this condition variable
  signal - Boolean value stating whether the condition is satisfied (indicated by 1) or not (0)
*/

typedef struct {
  int proccount;
  _Bool signal;
} pthread_cond_t;

/* pthread_t struct definition
  Description: The pthread_t is a struct containing a $proc variable as well as a thread attribute which defines
  its interactions with other threads. It encapsulates the $proc and allows attributes to apply to it.
  Fields: thr: the $proc variable that is the heart of the thread
  attr: see above
*/

typedef struct {
  $proc thr;
  const pthread_attr_t *attr;
} pthread_t;

/**
  * Initializes an attribute with the default values defined for it by an implementation.
  * Corresponding specification: p. 1532-4
  *
  * @param *attr
  *            The attribute to be initialized.
  * @return Returns 0 upon successful completion
  */

int pthread_attr_init(pthread_attr_t *attr){
  attr->stacksize = 0;
  attr->guardsize = 0;
  attr->detachstate = PTHREAD_CREATE_DETACHED;
  //attr->inheritsched = PTHREAD_EXPLICIT_SCHED;
  attr->contentionscope = PTHREAD_SCOPE_SYSTEM;
  attr->stackaddr = NULL;
  //attr->schedpolicy = SCHED_OTHER;
  return 0;
}

/**
  * Uninitializes the specified attr variable.
  * Corresponding specification: p. 1532-4
  *
  * @param *attr
  *            The attribute to be uninitialized.
  * @return Returns 0 upon successful completion
  */

int pthread_attr_destroy(pthread_attr_t *attr)
{ 
  pthread_attr_t blank;
  
  *attr = blank;
  return 0; 
}


/**
  * Sets the detachstate field of the attribute
  * Corresponding specification: p. 1535-6
  *
  * @param *attr
  *            The attribute to have it's detachstate set
  * @param detachstate
  *            The detachstate to which the attribute's detachstate is set  
  * @return Returns 0 upon successful completion
  */

int pthread_attr_setdetachstate(pthread_attr_t *attr, int detachstate)
{
  attr->detachstate = detachstate;
  return 0;
}

/**
  * Stores the detachstate value of the attribute in an alternate location
  * Corresponding specification: p. 1535-6
  *
  * @param *attr
  *            The attribute whose detachstate is to be stored
  * @param *detachstate
  *            The location at which the detachstate is to be stored  
  * @return Returns 0 upon successful completion
  */
  
int pthread_attr_getdetachstate(const pthread_attr_t *attr, int *detachstate)
{
  *detachstate = attr->detachstate;
  return 0;
}

/**
  * Set scheduling inheritance 
  * Corresponding specification: p. 1540-1
  *
  * @param *attr
  *            The attribute to have it's inheritsched set
  * @param inheritsched
  *            The inheritsched to which the attribute's inheritsched is set 
  * @return Returns 0 upon successful completion
  */

int pthread_attr_setinheritsched(pthread_attr_t *attr, int inheritsched)
{
  attr->inheritsched = inheritsched;
  return 0;
}

/**
  * Stores the inheritsched value of the attribute in an alternate location
  * Corresponding specification: p. 1540-1
  *
  * @param *attr
  *            The attribute whose inheritsched is to be stored
  * @param *intheritsched
  *            The location at which the attribute's inheritsched is to be stored  
  * @return Returns 0 upon successful completion
  */

int pthread_attr_getinheritsched(const pthread_attr_t *attr, int *inheritsched)
{
  *inheritsched = attr->inheritsched;
  return 0;
}

/**
  * Set contentionscope field of the attribute
  * Corresponding specification: p. 1546-7
  *
  * @param *attr
  *            The attribute to have it's contentionscope set
  * @param contentionscope
  *            The contentionscope to which the attribute's contentionscope is set  
  * @return Returns 0 upon successful completion
  */
 
int pthread_attr_setscope(pthread_attr_t *attr, int contentionscope)
{
  attr->contentionscope = contentionscope;
  return 0;
}

/**
  * Stores the contentionscope value of the attribute in an alternate location
  * Corresponding specification: p. 1546-7
  *
  * @param *attr
  *            The attribute whose contentionscope is to be stored
  * @param *contentionscope
  *            The location at which the attribute's contentionscope is to be stored  
  * @return Returns 0 upon successful completion
  */

int pthread_attr_getscope(const pthread_attr_t *attr, int *contentionscope)
{
  *contentionscope = attr->contentionscope;
  return 0;
}


/**
  * Sets the stack address and stacksize fields of the attribute
  * Corresponding specification: p. 1548-50
  *
  * @param *attr
  *            The attribute to have it's stack address and stack size set
  * @param *stackaddr
  *            The address to which the attribute's stack address is set  
  * @param stacksize
  *            The size to which the attribute's stack size is set  
  * @return Returns 0 upon successful completion
  */

int pthread_attr_setstack(pthread_attr_t *attr, void * stackaddr, size_t stacksize){ 
  attr->stackaddr = stackaddr;
  attr->stacksize = stacksize;
  return 0;
}

/**
  * Stores the stack address and size values in alternate locations
  * Corresponding specification: p. 1548-50
  *
  * @param *attr
  *            The attribute whose stack address and size are to be stored
  * @param **stackaddr
  *            The location at which the attribute's stackaddr is to be stored 
  * @param *stacksize
  *            The location at which the attribute's stacksize is to be stored   
  * @return Returns 0 upon successful completion
  */
// Get the stack size and stack address of the specified pthread_attr_t
// Corresponding specification p.1548
int pthread_attr_getstack(const pthread_attr_t *attr, void ** stackaddr, size_t *stacksize)
{
  *stackaddr = attr->stackaddr;
  *stacksize = attr->stacksize;
  return 0;
}

/**
  * Sets the guardsize field of the attribute
  * Corresponding specification: p. 1537-9
  *
  * @param *attr
  *            The attribute to have it's guardsize set
  * @param guardsize
  *            The guardsize to which the attribute's guardsize is set  
  * @return Returns 0 upon successful completion
  */
  
int pthread_attr_setguardsize(pthread_attr_t *attr, size_t guardsize)
{
  attr->guardsize = guardsize;
  return 0;
}

/**
  * Stores the guardsize value in an alternate location
  * Corresponding specification: p. 1537-9
  *
  * @param *attr
  *            The attribute whose guardsize is to be stored
  * @param *guardsize
  *            The location at which the attribute's guardsize is to be stored  
  * @return Returns 0 upon successful completion
  */

int pthread_attr_getguardsize(const pthread_attr_t *attr, size_t *guardsize)
{
  *guardsize = attr->guardsize;
  return 0;
}

/**
  * Sets the scheduling policy field of the attribute
  * Corresponding specification: p. 1544-45
  *
  * @param *attr
  *            The attribute to have it's scheduling policy set
  * @param policy
  *            The scheduling policy to which the attribute's scheduling policy is set  
  * @return Returns 0 upon successful completion
  */

int pthread_attr_setschedpolicy(pthread_attr_t *attr, int policy)
{
  attr->schedpolicy = policy;
  return 0;
}

/**
  * Stores the scheduling policy value in an alternate location
  * Corresponding specification: p. 1544-45
  *
  * @param *attr
  *            The attribute whose scheduling policy is to be stored
  * @param *policy
  *            The location at which the attribute's scheduling policy is to be stored  
  * @return Returns 0 upon successful completion
  */

int pthread_attr_getschedpolicy(const pthread_attr_t *attr, int *policy)
{
  *policy = attr->schedpolicy;
  return 0;
}

/**
  * Initializes an attribute with the default values defined for it by an implementation.
  * Corresponding specification: p. 1647-51
  *
  * @param *attr
  *            The attribute to be initialized.
  * @return Returns 0 upon successful completion
  */

int pthread_mutexattr_init(pthread_mutexattr_t *attr){
  attr->robust = 0;
  attr->pshared = 0;
  attr->protocol = 0;
  attr->type = 0;
  attr->prioceiling = 0;
  return 0;
}

/**
  * Uninitializes the specified attr variable.
  * Corresponding specification: p. 1647-51
  *
  * @param *attr
  *            The attribute to be uninitialized.
  * @return Returns 0 upon successful completion
  */

int pthread_mutexattr_destroy(pthread_mutexattr_t *attr){
  pthread_mutexattr_t blank;
  
  *attr = blank;
  return 0;
}

/**
  * Stores the robustness value in an alternate location
  * Corresponding specification: p. 1659-1660
  *
  * @param *attr
  *            The attribute whose robustness is to be stored
  * @param *robust
  *            The location at which the attribute's robustness is to be stored  
  * @return Returns 0 upon successful completion
  */

int pthread_mutexattr_getrobust(const pthread_mutexattr_t *attr, int *robust){
  *robust = attr->robust;
  return 0;
}

/**
  * Sets the robustness field of the attribute
  * Corresponding specification: p. 1659-1660
  *
  * @param *attr
  *            The attribute to have it's robustness set
  * @param robust
  *            The robustness to which the attribute's robustness is set  
  * @return Returns 0 upon successful completion
  */
  
int pthread_mutexattr_setrobust(pthread_mutexattr_t *attr, int robust){
  attr->robust = robust;
  return 0;
}

/**
  * Stores the process shared variable in an alternate location
  * Corresponding specification: p. 1657-8
  *
  * @param *attr
  *            The attribute whose process shared variable is to be stored
  * @param *detachstate
  *            The location at which the attribute's process shared variable is to be stored  
  * @return Returns 0 upon successful completion
  */
  
int pthread_mutexattr_getpshared(const pthread_mutexattr_t *attr, int *pshared){
  *pshared = attr->pshared;
  return 0;
}

/**
  * Sets the process shared variable field of the attribute
  * Corresponding specification: p. 1657-8
  *
  * @param *attr
  *            The attribute to have it's process shared variable set
  * @param detachstate
  *            The process shared variable to which the attribute's process shared variable is set  
  * @return Returns 0 upon successful completion
  */
  
int pthread_mutexattr_setpshared(pthread_mutexattr_t *attr, int pshared){
  attr->pshared = pshared;
  return 0;
}

/**
  * Stores the protocol value in an alternate location
  * Corresponding specification: p. 1654-56
  *
  * @param *attr
  *            The attribute whose protocol is to be stored
  * @param *detachstate
  *            The location at which the attribute's protocol is to be stored  
  * @return Returns 0 upon successful completion
  */
  
int pthread_mutexattr_getprotocol(const pthread_mutexattr_t *attr, int *protocol){
  *protocol = attr->protocol;
  return 0;
}

/**
  * Sets the protocol field of the attribute
  * Corresponding specification: p. 1654-56
  *
  * @param *attr
  *            The protocol to have it's protocol set
  * @param detachstate
  *            The protocol to which the attribute's protocol is set  
  * @return Returns 0 upon successful completion
  */
int pthread_mutexattr_setprotocol(pthread_mutexattr_t *attr, int protocol){
  attr->protocol = protocol;
  return 0;
}

/**
  * Stores the type value in an alternate location
  * Corresponding specification: p. 1709-10
  *
  * @param *attr
  *            The attribute whose type is to be stored
  * @param *detachstate
  *            The location at which the attribute's type is to be stored  
  * @return Returns 0 upon successful completion
  */
int pthread_mutexattr_gettype(const pthread_mutexattr_t *attr, int *type){
  *type = attr->type;
  return 0;
}

/**
  * Sets the type field of the attribute
  * Corresponding specification: p. 1709-10
  *
  * @param *attr
  *            The attribute to have it's type set
  * @param detachstate
  *            The type to which the attribute's type is set  
  * @return Returns 0 upon successful completion
  */
int pthread_mutexattr_settype(pthread_mutexattr_t *attr, int type){
  attr->type = type;
  return 0;
}

/**
  * Stores the priority ceiling value in an alternate location
  * Corresponding specification: p. 1700-1
  *
  * @param *attr
  *            The attribute whose priority ceiling is to be stored
  * @param *detachstate
  *            The location at which the attribute's priority ceiling is to be stored  
  * @return Returns 0 upon successful completion
  */
  
int pthread_mutexattr_getprioceiling(const pthread_mutexattr_t *attr, int *prioceiling){
  *prioceiling = attr->prioceiling;
  return 0;
}

/**
  * Sets the priority ceiling field of the attribute
  * Corresponding specification: p. 1700-1
  *
  * @param *attr
  *            The attribute to have it's priority ceiling set
  * @param detachstate
  *            The priority ceiling to which the attribute's priority ceiling is set  
  * @return Returns 0 upon successful completion
  */
  
int pthread_mutexattr_setprioceiling(pthread_mutexattr_t *attr, int prioceiling){
  attr->prioceiling = prioceiling;
  return 0;
}


/**
  * Initializes a mutex with the default values defined for it by an implementation
  * or with the values defined by the mutex attribute parameter
  * Corresponding specification: p. 1676-81
  *
  * @param *mutex
  *            The mutex to be initialized.
  * @param *attr
  *            The mutex attribute which the mutex shall take as it's field. May also
  *            be null for default values to be initialized.
  * @return Returns 0 upon successful completion
  */

int pthread_mutex_init(pthread_mutex_t *mutex, const pthread_mutexattr_t *attr){
  if(attr == NULL){
    mutex->attr = (pthread_mutexattr_t *)malloc(sizeof(pthread_mutexattr_t));
    mutex->attr->robust = 0;
    mutex->attr->pshared = 0;
    mutex->attr->protocol = 0;
    mutex->attr->type = PTHREAD_MUTEX_NORMAL;
    mutex->attr->prioceiling = 0;
  }
  else{
    mutex->attr = (pthread_mutexattr_t *)malloc(sizeof(pthread_mutexattr_t));
    mutex->attr = attr;
  }
  mutex->lock = 0;
  mutex->count = 0;
  mutex->owner = $proc_null;
  return 0;
}

/**
  * Uninitializes the specified mutex variable.
  * Corresponding specification: p. 1676-81
  *
  * @param *mutex
  *            The mutex to be uninitialized.
  * @return Returns 0 upon successful completion
  */

int pthread_mutex_destroy(pthread_mutex_t *mutex){
  pthread_mutex_t blank;
  
  *mutex = blank;
  return 0;
}

/**
  * Initializes an condition with the default values defined for it by an implementation.
  * Corresponding specification: p. 1630-32
  *
  * @param *cond
  *            The condition to be initialized.
  * @param *arg
  *            Should be changed to condition attribute
  * @return Returns 0 upon successful completion
  */

int pthread_cond_init(pthread_cond_t *cond, void *arg){
  cond->proccount = 0;
  cond->signal = 0;
  return 0;
}


/**
  * Uninitializes the specified cond variable.
  * Corresponding specification: p. 1630-2
  *
  * @param *cond
  *            The condition to be uninitialized.
  * @return Returns 0 upon successful completion
  */

int pthread_cond_destroy(pthread_cond_t *cond){
  if(cond->proccount != 0){
    $assert($false, "ERROR: Threads still waiting on specified condition variable");
  }
  else{
    pthread_cond_t blank;
    *cond = blank;
  }
  return 0;
}

/**
  * Defines a pthread_t by assigning it an attribute value (by value so the original attribute's state is
  * irrelevant), and spawning a process as the thr field with arguments void *arg
  * Corresponding specification: p. 1649-51
  *
  * @param *thread
  *            The thread to be created with fields set from the other parameters.
  * @param *attr
  *            The attribute to be assigned to the thread
  * @param *startroutine
  *            The process to be spawned as the thread's actual 'thread'
  * @param *arg
  *            The argument to be passed to the spawned function
  *
  * @return Returns 0 upon successful completion
  */

int pthread_create(pthread_t *thread, const pthread_attr_t *attr, void *(*start_routine)(void*), void *arg){
  thread->thr = $spawn start_routine(arg);
  if(attr == NULL){
    thread->attr = (pthread_attr_t *)malloc(sizeof(pthread_attr_t));
    thread->attr->stackaddr = NULL;
    thread->attr->stacksize = 0;
    thread->attr->guardsize = 0;
    thread->attr->detachstate = 1;
    thread->attr->inheritsched = 0;
    thread->attr->contentionscope = 0;
    thread->attr->schedpolicy = 0;
  }
  else{
    thread->attr = (pthread_attr_t *)malloc(sizeof(pthread_attr_t));
    thread->attr->stackaddr = attr->stackaddr;
    thread->attr->stacksize = attr->stacksize;
    thread->attr->guardsize = attr->guardsize;
    thread->attr->detachstate = attr->detachstate;
    thread->attr->inheritsched = attr->inheritsched;
    thread->attr->contentionscope = attr->contentionscope;
    thread->attr->schedpolicy = attr->schedpolicy;
  }
  return 0;
}

/**
  * Causes current thread to wait on thread specified as a parameter. If specified thread's detachstate field is set as PTHREAD_CREATE_DETACHED,
  * error will be returned stating the the thread cannot be joined. The value_ptr of pthread_exit shall be passed to any joining thread to the 
  * terminated thread using pthread_join's value_ptr
  * Corresponding specification: p. 1617-9
  *
  * @param thread
  *            The thread to be waited on by the current thread.
  * @param **value_ptr
  *            The location at which the pthread_exit output is accessible
  *
  * @return Returns 0 upon successful completion
  */

int pthread_join(pthread_t thread, void **value_ptr){
  if(thread.attr != NULL){
    if(thread.attr->detachstate == 0){
      $assert($false, "Thread is designated as unjoinable");
      return 1;
    }
  }
  $wait(thread.thr);
  if(value_ptr!=NULL)
    value_ptr = &value;
  return 0;
}

/**
  * Causes current thread to immediately terminate; if currently in the main method as specified by the 
  * isMain parameter, the main method will wait for each thread to terminate before it terminates. The value
  * value_ptr will be made accessible in the location stated in pthread_join
  * Corresponding specification: p. 1655-6
  *
  * @param *value_ptr
  *            The value to be stored in the location stated by pthread_join
  * @param isMain
  *            Is this thread the main thread?
  * @param *arr 
  *            The array of threads which need to be waited upon by the main thread
  * @param len
  *            The length of the array of threads to be waited upon
  * @return Returns 0 upon successful completion
  */

int pthread_exit(void *value_ptr, _Bool isMain, pthread_t *arr, int len){
  if(isMain){
    for(int i = 0; i<len; i++)
      $wait(arr[i].thr);
    $exit();
    return 0;
  }
  else{
    value = value_ptr;
    $exit();
    return 0;
  }
}

//Unimplemented
int pthread_detach(pthread_t thread);

/**
  * Takes in a mutex variable and acts accordingly to its current state and type
  * PTHREAD_MUTEX_NORMAL: Checks to see whether mutex is already locked and behaves accordingly
  *  locked and owner: Relock error, returns 0
  *  locked and not owner: Waits until mutex is unlocked and then locks and becomes owner
  *  unlocked and not owner: Locks the mutex and becomes owner
  * PTHREAD_MUTEX_RECURSIVE: A recursive mutex increments its count when it is locked and decremented when
  *  it is unlocked and the lock is released when the count reaches 0.
  * PTHREAD_MUTEX_ERRORCHECK: Implemented similarly to PTHREAD_MUTEX_NORMAL, but notifies the user of errors
  * Corresponding specification: p. 1686-9
  *
  * @param *mutex
  *            The mutex to be locked
  * @return Returns 0 upon successful completion, EOWNERDEAD upon termination of owner, 
  */

int pthread_mutex_lock(pthread_mutex_t *mutex){
  $atomic{
    if (mutex->attr->type == PTHREAD_MUTEX_NORMAL){
      if (mutex->lock != 0) {
        if(mutex->owner == $proc_null){
          if(mutex->attr->robust == PTHREAD_MUTEX_ROBUST){
            $when(mutex->lock == 0);
          }
          else{
            $assert($false);
            return EOWNERDEAD;
          }
        }
        else{
          if(mutex->owner == $self){
            $assert($false);
            return 0;
          }
          else{
            $when(mutex->lock == 0); 
          }
        }
      }
      mutex->owner = $self;
      mutex->lock = 1;
    } 
    else {
      int tmp = mutex->lock;
      
      mutex->lock = 1;
      if (tmp == 0) { // Attempts lock and checks for whether lock is already locked
        mutex->count = 1; 
        mutex->owner = $self;
      } 
      else {
        //Checks for ownership, otherwise returns error
        if(mutex->owner == $self){
          // Checks for recursive mutex, otherwise returns an error 
          if (mutex->attr->type == PTHREAD_MUTEX_RECURSIVE) {
            mutex->count++;
          }
          else {
            $assert($false);
            return 0;
          }
        }
        else {
          $assert($false, "ERROR: Relock attempted on non-recursive mutex\n");
          return 0;
        }
      }
    }
    return 0;
  }
}

/**
  * Takes in a mutex variable and acts similarly to pthread_mutex_lock except that 
  * if the mutex is locked, it will return immeditately. In the case of a recursive mutex, the count will
  * be incremented and will return successfully.
  * Corresponding specification: p. 1686-9
  *
  * @param *mutex
  *            The mutex to be locked
  * @return Returns 0 upon successful completion
  */

int pthread_mutex_trylock(pthread_mutex_t *mutex){
  $atomic{
    if (mutex->attr->type == PTHREAD_MUTEX_NORMAL){
      if (mutex->lock != 0) {
        return EBUSY;
      }
      mutex->owner = $self;
      mutex->lock = 1;
    } 
    else {
      int tmp = mutex->lock;
      
      mutex->lock = 1;
      if (tmp == 0) { // Attempts lock and checks for whether lock is already locked
        mutex->count = 1; 
        mutex->owner = $self;
      } 
      else {
        //Checks for ownership, otherwise returns error
        if(mutex->owner == $self){
          // Checks for recursive mutex, otherwise returns an error 
          if (mutex->attr->type == PTHREAD_MUTEX_RECURSIVE) {
            mutex->count++;
          }
          else {
            $assert($false);
            return 0;
          }
        }
        else {
          return EBUSY;
        }
      }
    }
    return 0;
  }
}

/**
  * Takes in a mutex variable and acts accordingly to its current state and type
  * PTHREAD_MUTEX_NORMAL: Checks to see whether mutex is already unlocked and behaves accordingly
  *  unlocked: returns error
  *  locked: unlocks
  * PTHREAD_MUTEX_RECURSIVE: A recursive mutex increments its count when it is locked and decremented when
  *  it is unlocked and the lock is released when the count reaches 0.
  * PTHREAD_MUTEX_ERRORCHECK: Currently implemented similarly to PTHREAD_MUTEX_NORMAL
  * Corresponding specification: p. 1686-9 
  *
  * @param *mutex
  *            The mutex to be unlocked
  * @return Returns 0 upon successful completion
  */

int pthread_mutex_unlock(pthread_mutex_t *mutex){
  $atomic{
    if (mutex->attr->type == 0 || mutex->attr->type == 2) {
      int idx;
      
      // Attempts unlock, if already unlocked, returns error
      if (mutex->lock == 0 && mutex->attr->type == PTHREAD_MUTEX_NORMAL) {
        $assert($false);
        return 0;
      }
      else if (mutex->lock == 0 && mutex->attr->type == PTHREAD_MUTEX_ERRORCHECK){
        $assert($false, "Attempting to unlock unlocked lock\n");
        return 0;
      }
      else {
        mutex->lock = 0;
        mutex->owner = $proc_null;
      }
    } 
    else {
      //Checks for ownership of thread, if not, returns error
      if(mutex->owner == $self)
      {
        //Checks for recursive mutex
        _Bool tmp = !(mutex->attr->type == 1);
        
        if (--mutex->count == 0){
          mutex->lock = 0;
          mutex->owner = $proc_null;
        }
      }
      else {
        $assert($false);
        return 0;
      }
    }
    return 0;
  }
}

/**
  * Checks for robustness of mutex: if robust, the mutex is unlocked, otherwise an error is caused
  * and EINVAL is returned
  * Corresponding specification: p. 1674-5
  *
  * @param *mutex
  *            The mutex to be marked as consistent
  * @return Returns 0 upon successful completion, EINVAL upon non-robust mutex input 
  */

int pthread_mutex_consistent(pthread_mutex_t *mutex){
  if(mutex->attr->robust == PTHREAD_MUTEX_ROBUST){
    mutex->lock = 0;
    return 0;
  }
  $assert($false);
  return EINVAL;
}

/**
  * Checks for calling thread as owner of the mutex, then increments proccount, unlocks the mutex 
  * and sleeps. Awakens upon signal and decrements proccount and locks mutex.
  * Corresponding specification: p. 1634-9
  *
  * @param *cond
  *            The condition to be waited upon until a signal is given
  * @param *mutex
  *            The mutex used to lock other threads out
  * @return Returns 0 upon successful completion, EINVAL upon non-robust mutex input 
  */

int pthread_cond_wait(pthread_cond_t *cond, pthread_mutex_t *mutex){
  if(mutex->owner != $self){
    printf("Mutex not owned by thread");
    $assert($false);
    return 0;
  }
  
  cond->proccount= cond->proccount+1;
  pthread_mutex_unlock(mutex);
  
  $when(cond->signal);
  cond->signal = false;
  --cond->proccount;
  $when(mutex->lock == 0){pthread_mutex_lock(mutex);}
  return 0;
}

/**
  * Signals the condition by setting the signal to true
  * Corresponding specification: p. 1627-30
  *
  * @param *cond
  *            The condition to be signalled
  * @return Returns 0 upon successful completion 
  */

int pthread_cond_signal(pthread_cond_t *cond){
  cond->signal = true;
  return 0;
}

/**
  * Repeated signals the condition until all processes waiting have been signalled and awoken
  * Corresponding specification: p. 1627-30
  *
  * @param *cond
  *            The condition to be signalled repeatedly
  * @return Returns 0 upon successful completion 
  */

int pthread_cond_broadcast(pthread_cond_t *cond){
  while(cond->proccount > 0){
    cond->signal = true;
  }
  return 0;
}