pool.cc

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/*
    Copyright (C) 1998-99 Paul Barton-Davis
 
    This program is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation; either version 2 of the License, or
    (at your option) any later version.

    This program 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
    GNU General Public License for more details.

    You should have received a copy of the GNU General Public License
    along with this program; if not, write to the Free Software
    Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.

    $Id$
*/

#include <cstdlib>
#include <vector>
#include <cstdlib>
#include <cassert>

#include "pbd/pool.h"
#include "pbd/pthread_utils.h"
#include "pbd/error.h"
#include "pbd/debug.h"
#include "pbd/compose.h"

using namespace std;
using namespace PBD;

Pool::Pool (string n, unsigned long item_size, unsigned long nitems)
        : free_list (nitems)
        , _name (n)
{
        _name = n;

        /* since some overloaded ::operator new() might use this,
           its important that we use a "lower level" allocator to
           get more space.  
        */

        block = malloc (nitems * item_size);

        void **ptrlist = (void **) malloc (sizeof (void *)  * nitems);

        for (unsigned long i = 0; i < nitems; i++) {
                ptrlist[i] = static_cast<void *> (static_cast<char*>(block) + (i * item_size));
        }

        free_list.write (ptrlist, nitems);
        free (ptrlist);
}

Pool::~Pool ()
{
        free (block);
}

void *
Pool::alloc ()
{
        void *ptr;

        if (free_list.read (&ptr, 1) < 1) {
                fatal << "CRITICAL: " << _name << " POOL OUT OF MEMORY - RECOMPILE WITH LARGER SIZE!!" << endmsg;
                abort(); /*NOTREACHED*/
                return 0;
        } else {
                return ptr;
        }
}

void            
Pool::release (void *ptr)
{
        free_list.write (&ptr, 1);
}

/*---------------------------------------------*/

MultiAllocSingleReleasePool::MultiAllocSingleReleasePool (string n, unsigned long isize, unsigned long nitems) 
        : Pool (n, isize, nitems)
{
}

MultiAllocSingleReleasePool::~MultiAllocSingleReleasePool ()
{
}

SingleAllocMultiReleasePool::SingleAllocMultiReleasePool (string n, unsigned long isize, unsigned long nitems) 
        : Pool (n, isize, nitems)
{
}

SingleAllocMultiReleasePool::~SingleAllocMultiReleasePool ()
{
}

void*
MultiAllocSingleReleasePool::alloc ()
{
        void *ptr;
        Glib::Threads::Mutex::Lock guard (m_lock);
        ptr = Pool::alloc ();
        return ptr;
}

void
MultiAllocSingleReleasePool::release (void* ptr)
{
        Pool::release (ptr);
}

void*
SingleAllocMultiReleasePool::alloc ()
{
        return Pool::alloc ();
}

void
SingleAllocMultiReleasePool::release (void* ptr)
{
        Glib::Threads::Mutex::Lock guard (m_lock);
        Pool::release (ptr);
}

/*-------------------------------------------------------*/

static void 
free_per_thread_pool (void* ptr)
{
        /* Rather than deleting the CrossThreadPool now, we add it to our trash buffer.
         * This prevents problems if other threads still require access to this CrossThreadPool.
         * We assume that some other agent will clean out the trash buffer as required.
         */
        CrossThreadPool* cp = static_cast<CrossThreadPool*> (ptr);
        assert (cp);

        if (cp->empty()) {
                /* This CrossThreadPool is already empty, and the thread is finishing so nothing
                 * more can be added to it.  We can just delete the pool.
                 */
                delete cp;
        } else {
                /* This CrossThreadPool is not empty, meaning that there's some Events in it
                 * which another thread may yet read, so we can't delete the pool just yet.
                 * Put it in the trash and hope someone deals with it at some stage.
                 */
                cp->parent()->add_to_trash (cp);
        }
}
 
PerThreadPool::PerThreadPool ()
        : _key (free_per_thread_pool)
        , _trash (0)
{
}

void
PerThreadPool::create_per_thread_pool (string n, unsigned long isize, unsigned long nitems)
{
        _key.set (new CrossThreadPool (n, isize, nitems, this));
}

CrossThreadPool*
PerThreadPool::per_thread_pool (bool must_exist)
{
        CrossThreadPool* p = _key.get();
        if (!p && must_exist) {
                fatal << "programming error: no per-thread pool \"" << _name << "\" for thread " << pthread_name() << endmsg;
                abort(); /*NOTREACHED*/
        }
        return p;
}

void
PerThreadPool::set_trash (RingBuffer<CrossThreadPool*>* t)
{
        Glib::Threads::Mutex::Lock lm (_trash_mutex);
        _trash = t;
}

void
PerThreadPool::add_to_trash (CrossThreadPool* p)
{
        Glib::Threads::Mutex::Lock lm (_trash_mutex);
        
        if (!_trash) {
                warning << "Pool " << p->name() << " has no trash collector; a memory leak has therefore occurred" << endmsg;
                return;
        }

        /* we have a lock here so that multiple threads can safely call add_to_trash (even though there
           can only be one writer to the _trash RingBuffer)
        */
                
        _trash->write (&p, 1);
}

CrossThreadPool::CrossThreadPool  (string n, unsigned long isize, unsigned long nitems, PerThreadPool* p)
        : Pool (n, isize, nitems)
        , pending (nitems)
        , _parent (p)
{
        
}

void
CrossThreadPool::flush_pending_with_ev (void *ptr)
{
        push (ptr);
        flush_pending ();
}

void
CrossThreadPool::flush_pending ()
{
        void* ptr;
        bool did_release = false;
        
        DEBUG_TRACE (DEBUG::Pool, string_compose ("%1 %2 has %3 pending free entries waiting, status size %4 free %5 used %6\n", pthread_name(), name(), pending.read_space(),
                                                  total(), available(), used()));
                                                  
        while (pending.read (&ptr, 1) == 1) {
                DEBUG_TRACE (DEBUG::Pool, string_compose ("%1 %2 pushes back a pending free list entry before allocating\n", pthread_name(), name()));
                free_list.write (&ptr, 1);
                did_release = true;
        }

        if (did_release) {
                DEBUG_TRACE (DEBUG::Pool, string_compose ("Pool size: %1 free %2 used %3 pending now %4\n", total(), available(), used(), pending_size()));
        }
}

void*
CrossThreadPool::alloc () 
{
        /* process anything waiting to be deleted (i.e. moved back to the free list)  */
        flush_pending ();
        /* now allocate from the potentially larger free list */
        return Pool::alloc ();
}

void
CrossThreadPool::push (void* t) 
{
        pending.write (&t, 1);
}

bool
CrossThreadPool::empty ()
{
        return (free_list.write_space() == pending.read_space());
}