1: /* Copyright (C) 2003, 2004, 2006, 2007 Free Software Foundation, Inc.
    2:    This file is part of the GNU C Library.
    3:    Contributed by Martin Schwidefsky <schwidefsky@de.ibm.com>, 2003.
    4: 
    5:    The GNU C Library is free software; you can redistribute it and/or
    6:    modify it under the terms of the GNU Lesser General Public
    7:    License as published by the Free Software Foundation; either
    8:    version 2.1 of the License, or (at your option) any later version.
    9: 
   10:    The GNU C Library is distributed in the hope that it will be useful,
   11:    but WITHOUT ANY WARRANTY; without even the implied warranty of
   12:    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   13:    Lesser General Public License for more details.
   14: 
   15:    You should have received a copy of the GNU Lesser General Public
   16:    License along with the GNU C Library; if not, write to the Free
   17:    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
   18:    02111-1307 USA.  */
   19: 
   20: #include <endian.h>
   21: #include <errno.h>
   22: #include <sysdep.h>
   23: #include <lowlevellock.h>
   24: #include <pthread.h>
   25: #include <pthreadP.h>
   26: 
   27: #include <shlib-compat.h>
   28: 
   29: 
   30: struct _condvar_cleanup_buffer
   31: {
   32:   int oldtype;
   33:   pthread_cond_t *cond;
   34:   pthread_mutex_t *mutex;
   35:   unsigned int bc_seq;
   36: };
   37: 
   38: 
   39: void
   40: __attribute__ ((visibility ("hidden")))
   41: __condvar_cleanup (void *arg)
   42: {
   43:   struct _condvar_cleanup_buffer *cbuffer =
   44:     (struct _condvar_cleanup_buffer *) arg;
   45:   unsigned int destroying;
   46:   int pshared = (cbuffer->cond->__data.__mutex == (void *) ~0l)
   47:                 ? LLL_SHARED : LLL_PRIVATE;
   48: 
   49:   /* We are going to modify shared data.  */
   50:   lll_lock (cbuffer->cond->__data.__lock, pshared);
   51: 
   52:   if (cbuffer->bc_seq == cbuffer->cond->__data.__broadcast_seq)
   53:     {
   54:       /* This thread is not waiting anymore.  Adjust the sequence counters
   55:          appropriately.  We do not increment WAKEUP_SEQ if this would
   56:          bump it over the value of TOTAL_SEQ.  This can happen if a thread
   57:          was woken and then canceled.  */
   58:       if (cbuffer->cond->__data.__wakeup_seq
   59:           < cbuffer->cond->__data.__total_seq)
   60:         {
   61:           ++cbuffer->cond->__data.__wakeup_seq;
   62:           ++cbuffer->cond->__data.__futex;
   63:         }
   64:       ++cbuffer->cond->__data.__woken_seq;
   65:     }
   66: 
   67:   cbuffer->cond->__data.__nwaiters -= 1 << COND_NWAITERS_SHIFT;
   68: 
   69:   /* If pthread_cond_destroy was called on this variable already,
   70:      notify the pthread_cond_destroy caller all waiters have left
   71:      and it can be successfully destroyed.  */
   72:   destroying = 0;
   73:   if (cbuffer->cond->__data.__total_seq == -1ULL
   74:       && cbuffer->cond->__data.__nwaiters < (1 << COND_NWAITERS_SHIFT))
   75:     {
   76:       lll_futex_wake (&cbuffer->cond->__data.__nwaiters, 1, pshared);
   77:       destroying = 1;
   78:     }
   79: 
   80:   /* We are done.  */
   81:   lll_unlock (cbuffer->cond->__data.__lock, pshared);
   82: 
   83:   /* Wake everybody to make sure no condvar signal gets lost.  */
   84:   if (! destroying)
   85:     lll_futex_wake (&cbuffer->cond->__data.__futex, INT_MAX, pshared);
   86: 
   87:   /* Get the mutex before returning unless asynchronous cancellation
   88:      is in effect.  */
   89:   __pthread_mutex_cond_lock (cbuffer->mutex);
   90: }
   91: 
   92: 
   93: int
   94: __pthread_cond_wait (cond, mutex)
   95:      pthread_cond_t *cond;
   96:      pthread_mutex_t *mutex;
   97: {
   98:   struct _pthread_cleanup_buffer buffer;
   99:   struct _condvar_cleanup_buffer cbuffer;
  100:   int err;
  101:   int pshared = (cond->__data.__mutex == (void *) ~0l)
  102:                 ? LLL_SHARED : LLL_PRIVATE;
  103: 
  104:   /* Make sure we are along.  */
  105:   lll_lock (cond->__data.__lock, pshared);
  106: 
  107:   /* Now we can release the mutex.  */
  108:   err = __pthread_mutex_unlock_usercnt (mutex, 0);
  109:   if (__builtin_expect (err, 0))
  110:     {
  111:       lll_unlock (cond->__data.__lock, pshared);
  112:       return err;
  113:     }
  114: 
  115:   /* We have one new user of the condvar.  */
  116:   ++cond->__data.__total_seq;
  117:   ++cond->__data.__futex;
  118:   cond->__data.__nwaiters += 1 << COND_NWAITERS_SHIFT;
  119: 
  120:   /* Remember the mutex we are using here.  If there is already a
  121:      different address store this is a bad user bug.  Do not store
  122:      anything for pshared condvars.  */
  123:   if (cond->__data.__mutex != (void *) ~0l)
  124:     cond->__data.__mutex = mutex;
  125: 
  126:   /* Prepare structure passed to cancellation handler.  */
  127:   cbuffer.cond = cond;
  128:   cbuffer.mutex = mutex;
  129: 
  130:   /* Before we block we enable cancellation.  Therefore we have to
  131:      install a cancellation handler.  */
  132:   __pthread_cleanup_push (&buffer, __condvar_cleanup, &cbuffer);
  133: 
  134:   /* The current values of the wakeup counter.  The "woken" counter
  135:      must exceed this value.  */
  136:   unsigned long long int val;
  137:   unsigned long long int seq;
  138:   val = seq = cond->__data.__wakeup_seq;
  139:   /* Remember the broadcast counter.  */
  140:   cbuffer.bc_seq = cond->__data.__broadcast_seq;
  141: 
  142:   do
  143:     {
  144:       unsigned int futex_val = cond->__data.__futex;
  145: 
  146:       /* Prepare to wait.  Release the condvar futex.  */
  147:       lll_unlock (cond->__data.__lock, pshared);
  148: 
  149:       /* Enable asynchronous cancellation.  Required by the standard.  */
  150:       cbuffer.oldtype = __pthread_enable_asynccancel ();
  151: 
  152:       /* Wait until woken by signal or broadcast.  */
  153:       lll_futex_wait (&cond->__data.__futex, futex_val, pshared);
  154: 
  155:       /* Disable asynchronous cancellation.  */
  156:       __pthread_disable_asynccancel (cbuffer.oldtype);
  157: 
  158:       /* We are going to look at shared data again, so get the lock.  */
  159:       lll_lock (cond->__data.__lock, pshared);
  160: 
  161:       /* If a broadcast happened, we are done.  */
  162:       if (cbuffer.bc_seq != cond->__data.__broadcast_seq)
  163:         goto bc_out;
  164: 
  165:       /* Check whether we are eligible for wakeup.  */
  166:       val = cond->__data.__wakeup_seq;
  167:     }
  168:   while (val == seq || cond->__data.__woken_seq == val);
  169: 
  170:   /* Another thread woken up.  */
  171:   ++cond->__data.__woken_seq;
  172: 
  173:  bc_out:
  174: 
  175:   cond->__data.__nwaiters -= 1 << COND_NWAITERS_SHIFT;
  176: 
  177:   /* If pthread_cond_destroy was called on this varaible already,
  178:      notify the pthread_cond_destroy caller all waiters have left
  179:      and it can be successfully destroyed.  */
  180:   if (cond->__data.__total_seq == -1ULL
  181:       && cond->__data.__nwaiters < (1 << COND_NWAITERS_SHIFT))
  182:     lll_futex_wake (&cond->__data.__nwaiters, 1, pshared);
  183: 
  184:   /* We are done with the condvar.  */
  185:   lll_unlock (cond->__data.__lock, pshared);
  186: 
  187:   /* The cancellation handling is back to normal, remove the handler.  */
  188:   __pthread_cleanup_pop (&buffer, 0);
  189: 
  190:   /* Get the mutex before returning.  */
  191:   return __pthread_mutex_cond_lock (mutex);
  192: }
  193: 
  194: versioned_symbol (libpthread, __pthread_cond_wait, pthread_cond_wait,
  195:                   GLIBC_2_3_2);