Python/thread_pth.h

   1
   2 /* GNU pth threads interface
   3    http://www.gnu.org/software/pth
   4    2000-05-03 Andy Dustman <andy@dustman.net>
   5
   6    Adapted from Posix threads interface
   7    12 May 1997 -- david arnold <davida@pobox.com>
   8  */
   9
  10 #include <stdlib.h>
  11 #include <string.h>
  12 #include <pth.h>
  13
  14 /* A pth mutex isn't sufficient to model the Python lock type
  15  * because pth mutexes can be acquired multiple times by the
  16  * same thread.
  17  *
  18  * The pth_lock struct implements a Python lock as a "locked?" bit
  19  * and a <condition, mutex> pair.  In general, if the bit can be acquired
  20  * instantly, it is, else the pair is used to block the thread until the
  21  * bit is cleared.
  22  */
  23
  24 typedef struct {
  25     char             locked; /* 0=unlocked, 1=locked */
  26     /* a <cond, mutex> pair to handle an acquire of a locked lock */
  27     pth_cond_t   lock_released;
  28     pth_mutex_t  mut;
  29 } pth_lock;
  30
  31 #define CHECK_STATUS(name)  if (status == -1) { printf("%d ", status); perror(name); error = 1; }
  32
  33 pth_attr_t PyThread_attr;
  34
  35 /*
  36  * Initialization.
  37  */
  38
  39 static void PyThread__init_thread(void)
  40 {
  41     pth_init();
  42     PyThread_attr = pth_attr_new();
  43     pth_attr_set(PyThread_attr, PTH_ATTR_STACK_SIZE, 1<<18);
  44     pth_attr_set(PyThread_attr, PTH_ATTR_JOINABLE, FALSE);
  45 }
  46
  47 /*
  48  * Thread support.
  49  */
  50
  51
  52 long PyThread_start_new_thread(void (*func)(void *), void *arg)
  53 {
  54     pth_t th;
  55     dprintf(("PyThread_start_new_thread called\n"));
  56     if (!initialized)
  57         PyThread_init_thread();
  58
  59     th = pth_spawn(PyThread_attr,
  60                              (void* (*)(void *))func,
  61                              (void *)arg
  62                              );
  63
  64     return th;
  65 }
  66
  67 long PyThread_get_thread_ident(void)
  68 {
  69     volatile pth_t threadid;
  70     if (!initialized)
  71         PyThread_init_thread();
  72     /* Jump through some hoops for Alpha OSF/1 */
  73     threadid = pth_self();
  74     return (long) *(long *) &threadid;
  75 }
  76
  77 void PyThread_exit_thread(void)
  78 {
  79     dprintf(("PyThread_exit_thread called\n"));
  80     if (!initialized) {
  81         exit(0);
  82     }
  83 }
  84
  85 /*
  86  * Lock support.
  87  */
  88 PyThread_type_lock PyThread_allocate_lock(void)
  89 {
  90     pth_lock *lock;
  91     int status, error = 0;
  92
  93     dprintf(("PyThread_allocate_lock called\n"));
  94     if (!initialized)
  95         PyThread_init_thread();
  96
  97     lock = (pth_lock *) malloc(sizeof(pth_lock));
  98     memset((void *)lock, '\0', sizeof(pth_lock));
  99     if (lock) {
 100         lock->locked = 0;
 101         status = pth_mutex_init(&lock->mut);
 102         CHECK_STATUS("pth_mutex_init");
 103         status = pth_cond_init(&lock->lock_released);
 104         CHECK_STATUS("pth_cond_init");
 105         if (error) {
 106             free((void *)lock);
 107             lock = NULL;
 108         }
 109     }
 110     dprintf(("PyThread_allocate_lock() -> %p\n", lock));
 111     return (PyThread_type_lock) lock;
 112 }
 113
 114 void PyThread_free_lock(PyThread_type_lock lock)
 115 {
 116     pth_lock *thelock = (pth_lock *)lock;
 117
 118     dprintf(("PyThread_free_lock(%p) called\n", lock));
 119
 120     free((void *)thelock);
 121 }
 122
 123 int PyThread_acquire_lock(PyThread_type_lock lock, int waitflag)
 124 {
 125     int success;
 126     pth_lock *thelock = (pth_lock *)lock;
 127     int status, error = 0;
 128
 129     dprintf(("PyThread_acquire_lock(%p, %d) called\n", lock, waitflag));
 130
 131     status = pth_mutex_acquire(&thelock->mut, !waitflag, NULL);
 132     CHECK_STATUS("pth_mutex_acquire[1]");
 133     success = thelock->locked == 0;
 134     if (success) thelock->locked = 1;
 135     status = pth_mutex_release( &thelock->mut );
 136     CHECK_STATUS("pth_mutex_release[1]");
 137
 138     if ( !success && waitflag ) {
 139         /* continue trying until we get the lock */
 140
 141         /* mut must be locked by me -- part of the condition
 142          * protocol */
 143         status = pth_mutex_acquire( &thelock->mut, !waitflag, NULL );
 144         CHECK_STATUS("pth_mutex_acquire[2]");
 145         while ( thelock->locked ) {
 146             status = pth_cond_await(&thelock->lock_released,
 147                                     &thelock->mut, NULL);
 148             CHECK_STATUS("pth_cond_await");
 149         }
 150         thelock->locked = 1;
 151         status = pth_mutex_release( &thelock->mut );
 152         CHECK_STATUS("pth_mutex_release[2]");
 153         success = 1;
 154     }
 155     if (error) success = 0;
 156     dprintf(("PyThread_acquire_lock(%p, %d) -> %d\n", lock, waitflag, success));
 157     return success;
 158 }
 159
 160 void PyThread_release_lock(PyThread_type_lock lock)
 161 {
 162     pth_lock *thelock = (pth_lock *)lock;
 163     int status, error = 0;
 164
 165     dprintf(("PyThread_release_lock(%p) called\n", lock));
 166
 167     status = pth_mutex_acquire( &thelock->mut, 0, NULL );
 168     CHECK_STATUS("pth_mutex_acquire[3]");
 169
 170     thelock->locked = 0;
 171
 172     status = pth_mutex_release( &thelock->mut );
 173     CHECK_STATUS("pth_mutex_release[3]");
 174
 175     /* wake up someone (anyone, if any) waiting on the lock */
 176     status = pth_cond_notify( &thelock->lock_released, 0 );
 177     CHECK_STATUS("pth_cond_notify");
 178 }