Comparing the win32 barrier to the pthread barrier, win32 puts the
while in an else clause. When if is true the phase changes and the
while condition will always by false, so might as well put the while
in the else to skip the check. There's also a benefit to having the
code logic similar between platforms.
SprocBarrier.c++ is the same as pthreads without the else, I just
don't like to submit changes without being able to at least compile
it.
win32:
my_phase = pd->phase;
if(pd->cnt == pd->maxcnt) {
pd->phase = 1 - my_phase;
...broadcast...
} else {
while(pd->phase == my_phase) {
...wait...
}
}
pthreads:
my_phase = pd->phase;
if(pd->cnt == pd->maxcnt) {
pd->phase = 1 - my_phase;
...broadcast...
}
while(pd->phase == my_phase) {
...wait...
}
Index: src/OpenThreads/pthreads/PThreadBarrier.c++
===================================================================
--- src/OpenThreads/pthreads/PThreadBarrier.c++ (revision 10273)
+++ src/OpenThreads/pthreads/PThreadBarrier.c++ (working copy)
@@ -173,15 +173,15 @@
pd->cnt = 0; // reset for next use
pd->phase = 1 - my_phase; // toggle phase
pthread_cond_broadcast(&(pd->cond));
- }
+ }else{
+ while (pd->phase == my_phase) {
- while (pd->phase == my_phase) {
+ pthread_cleanup_push(barrier_cleanup_handler, &(pd->lock));
- pthread_cleanup_push(barrier_cleanup_handler, &(pd->lock));
-
- pthread_cond_wait(&(pd->cond), &(pd->lock));
+ pthread_cond_wait(&(pd->cond), &(pd->lock));
- pthread_cleanup_pop(0);
+ pthread_cleanup_pop(0);
+ }
}
}
--
David Fries <[email protected]>
http://fries.net/~david/ (PGP encryption key available)
/* -*-c++-*- OpenThreads library, Copyright (C) 2002 - 2007 The Open Thread Group
*
* This library is open source and may be redistributed and/or modified under
* the terms of the OpenSceneGraph Public License (OSGPL) version 0.0 or
* (at your option) any later version. The full license is in LICENSE file
* included with this distribution, and on the openscenegraph.org website.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* OpenSceneGraph Public License for more details.
*/
//
// PThreadBarrier.c++ - C++ Barrier class built on top of POSIX threads.
// ~~~~~~~~~~~~~~~~~~
//
#include <stdio.h>
#include <unistd.h>
#include <OpenThreads/Barrier>
#include "PThreadBarrierPrivateData.h"
using namespace OpenThreads;
//----------------------------------------------------------------------------
// This cancel cleanup handler is necessary to ensure that the barrier's
// mutex gets unlocked on cancel. Otherwise deadlocks could occur with
// later joins.
//
void barrier_cleanup_handler(void *arg) {
pthread_mutex_t *mutex = static_cast<pthread_mutex_t *>(arg);
pthread_mutex_unlock(mutex);
}
//----------------------------------------------------------------------------
//
// Description: Constructor
//
// Use: public.
//
Barrier::Barrier(int numThreads) {
PThreadBarrierPrivateData *pd = new PThreadBarrierPrivateData();
pd->cnt = 0;
pd->phase = 0;
pd->maxcnt = numThreads;
_valid = true;
pthread_mutexattr_t mutex_attr;
pthread_mutexattr_init( &mutex_attr );
#ifndef __linux__ // (not available until NPTL) [
pthread_mutexattr_settype( &mutex_attr, PTHREAD_MUTEX_ERRORCHECK );
#endif // ] __linux__
#ifdef ALLOW_PRIORITY_SCHEDULING // [
#ifdef __sun // [
pthread_mutexattr_setprotocol(&mutex_attr, PTHREAD_PRIO_NONE);
#endif // ] __sun
//-------------------------------------------------------------------------
// Initialization is a bit tricky, since we have to be able to be aware
// that on many-to-many execution vehicle systems, we may run into
// priority inversion deadlocks if a mutex is shared between threads
// of differing priorities. Systems that do this should provide the
// following protocol attributes to prevent deadlocks. Check at runtime.
//
// PRIO_INHERIT causes any thread locking the mutex to temporarily become
// the same priority as the highest thread also blocked on the mutex.
// Although more expensive, this is the prefered method.
//
// PRIO_PROTECT causes any thread locking the mutex to assume the priority
// specified by setprioceiling. pthread_mutex_lock will fail if
// the priority ceiling is lower than the thread's priority. Therefore,
// the priority ceiling must be set to the max priority in order to
// garantee no deadlocks will occur.
//
#if defined (_POSIX_THREAD_PRIO_INHERIT) || defined (_POSIX_THREAD_PRIO_PROTECT) // [
if(sysconf(_POSIX_THREAD_PRIO_INHERIT)) {
pthread_mutexattr_setprotocol(&mutex_attr, PTHREAD_PRIO_INHERIT);
} else if (sysconf(_POSIX_THREAD_PRIO_PROTECT)) {
int th_policy;
struct sched_param th_param;
pthread_getschedparam(pthread_self(), &th_policy, &th_param);
pthread_mutexattr_setprotocol(&mutex_attr, PTHREAD_PRIO_PROTECT);
pthread_mutexattr_setprioceiling(&mutex_attr,
sched_get_priority_max(th_policy));
}
#endif // ] Priority sheduling
#endif // ] ALLOW_PRIORITY_SCHEDULING
pthread_mutex_init(&(pd->lock), &mutex_attr);
pthread_cond_init(&(pd->cond), NULL);
_prvData = static_cast<void *>(pd);
}
//----------------------------------------------------------------------------
//
// Description: Destructor
//
// Use: public.
//
Barrier::~Barrier() {
PThreadBarrierPrivateData *pd =
static_cast<PThreadBarrierPrivateData*>(_prvData);
pthread_mutex_destroy(&(pd->lock));
pthread_cond_destroy(&(pd->cond));
delete pd;
}
//----------------------------------------------------------------------------
//
// Description: Reset the barrier to its original state
//
// Use: public.
//
void Barrier::reset() {
PThreadBarrierPrivateData *pd =
static_cast<PThreadBarrierPrivateData*>(_prvData);
pd->cnt = 0;
pd->phase = 0;
}
//----------------------------------------------------------------------------
//
// Description: Block until numThreads threads have entered the barrier.
//
// Use: public.
//
void Barrier::block(unsigned int numThreads) {
PThreadBarrierPrivateData *pd =
static_cast<PThreadBarrierPrivateData*>(_prvData);
if(numThreads != 0) pd->maxcnt = numThreads;
int my_phase;
pthread_mutex_lock(&(pd->lock));
if( _valid )
{
my_phase = pd->phase;
++pd->cnt;
if (pd->cnt == pd->maxcnt) { // I am the last one
pd->cnt = 0; // reset for next use
pd->phase = 1 - my_phase; // toggle phase
pthread_cond_broadcast(&(pd->cond));
}else{
while (pd->phase == my_phase) {
pthread_cleanup_push(barrier_cleanup_handler, &(pd->lock));
pthread_cond_wait(&(pd->cond), &(pd->lock));
pthread_cleanup_pop(0);
}
}
}
pthread_mutex_unlock(&(pd->lock));
}
void Barrier::invalidate()
{
PThreadBarrierPrivateData *pd =
static_cast<PThreadBarrierPrivateData*>(_prvData);
pthread_mutex_lock(&(pd->lock));
_valid = false;
pthread_mutex_unlock(&(pd->lock));
release();
}
//----------------------------------------------------------------------------
//
// Description: Release the barrier, now.
//
// Use: public.
//
void Barrier::release() {
PThreadBarrierPrivateData *pd =
static_cast<PThreadBarrierPrivateData*>(_prvData);
int my_phase;
pthread_mutex_lock(&(pd->lock));
my_phase = pd->phase;
pd->cnt = 0; // reset for next use
pd->phase = 1 - my_phase; // toggle phase
pthread_cond_broadcast(&(pd->cond));
pthread_mutex_unlock(&(pd->lock));
}
//----------------------------------------------------------------------------
//
// Description: Return the number of threads currently blocked in the barrier
//
// Use: public
//
int Barrier::numThreadsCurrentlyBlocked() {
PThreadBarrierPrivateData *pd = static_cast<PThreadBarrierPrivateData*>(_prvData);
int numBlocked = -1;
pthread_mutex_lock(&(pd->lock));
numBlocked = pd->cnt;
pthread_mutex_unlock(&(pd->lock));
return numBlocked;
}
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