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/*
* ptw32_threadReuse.c
*
* Description:
* This translation unit implements miscellaneous thread functions.
*
* --------------------------------------------------------------------------
*
* Pthreads4w - POSIX Threads Library for Win32
* Copyright(C) 1998 John E. Bossom
* Copyright(C) 1999-2018, Pthreads4w contributors
*
* Homepage: https://sourceforge.net/projects/pthreads4w/
*
* The current list of contributors is contained
* in the file CONTRIBUTORS included with the source
* code distribution. The list can also be seen at the
* following World Wide Web location:
* https://sourceforge.net/p/pthreads4w/wiki/Contributors/
*
* This file is part of Pthreads4w.
*
* Pthreads4w 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 3 of the License, or
* (at your option) any later version.
*
* Pthreads4w 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 Pthreads4w. If not, see <http://www.gnu.org/licenses/>. *
*/
#ifdef HAVE_CONFIG_H
# include <config.h>
#endif
#include "pthread.h"
#include "implement.h"
/*
* How it works:
* A pthread_t is a struct (2x32 bit scalar types on x86, 2x64 bit on x86_64)
* [FIXME: This is not true, x86_64 is 64 bit pointer and 32 bit counter. This
* should be fixed in version 3.0.0]
* which is normally passed/returned by value to/from pthreads routines.
* Applications are therefore storing a copy of the struct as it is at that
* time.
*
* The original pthread_t struct plus all copies of it contain the address of
* the thread state struct ptw32_thread_t_ (p), plus a reuse counter (x). Each
* ptw32_thread_t contains the original copy of it's pthread_t (ptHandle).
* Once malloced, a ptw32_thread_t_ struct is not freed until the process exits.
*
* The thread reuse stack is a simple LILO stack managed through a singly
* linked list element in the ptw32_thread_t.
*
* Each time a thread is destroyed, the ptw32_thread_t address is pushed onto the
* reuse stack after it's ptHandle's reuse counter has been incremented.
*
* The following can now be said from this:
* - two pthread_t's refer to the same thread iff their ptw32_thread_t reference
* pointers are equal and their reuse counters are equal. That is,
*
* equal = (a.p == b.p && a.x == b.x)
*
* - a pthread_t copy refers to a destroyed thread if the reuse counter in
* the copy is not equal to (i.e less than) the reuse counter in the original.
*
* threadDestroyed = (copy.x != ((ptw32_thread_t *)copy.p)->ptHandle.x)
*
*/
/*
* Pop a clean pthread_t struct off the reuse stack.
*/
pthread_t
ptw32_threadReusePop (void)
{
pthread_t t = {NULL, 0};
ptw32_mcs_local_node_t node;
ptw32_mcs_lock_acquire(&ptw32_thread_reuse_lock, &node);
if (PTW32_THREAD_REUSE_EMPTY != ptw32_threadReuseTop)
{
ptw32_thread_t * tp;
tp = ptw32_threadReuseTop;
ptw32_threadReuseTop = tp->prevReuse;
if (PTW32_THREAD_REUSE_EMPTY == ptw32_threadReuseTop)
{
ptw32_threadReuseBottom = PTW32_THREAD_REUSE_EMPTY;
}
tp->prevReuse = NULL;
t = tp->ptHandle;
}
ptw32_mcs_lock_release(&node);
return t;
}
/*
* Push a clean pthread_t struct onto the reuse stack.
* Must be re-initialised when reused.
* All object elements (mutexes, events etc) must have been either
* destroyed before this, or never initialised.
*/
void
ptw32_threadReusePush (pthread_t thread)
{
ptw32_thread_t * tp = (ptw32_thread_t *) thread.p;
pthread_t t;
ptw32_mcs_local_node_t node;
ptw32_mcs_lock_acquire(&ptw32_thread_reuse_lock, &node);
t = tp->ptHandle;
memset(tp, 0, sizeof(ptw32_thread_t));
/* Must restore the original POSIX handle that we just wiped. */
tp->ptHandle = t;
/* Bump the reuse counter now */
#if defined(PTW32_THREAD_ID_REUSE_INCREMENT)
tp->ptHandle.x += PTW32_THREAD_ID_REUSE_INCREMENT;
#else
tp->ptHandle.x++;
#endif
tp->state = PThreadStateReuse;
tp->prevReuse = PTW32_THREAD_REUSE_EMPTY;
if (PTW32_THREAD_REUSE_EMPTY != ptw32_threadReuseBottom)
{
ptw32_threadReuseBottom->prevReuse = tp;
}
else
{
ptw32_threadReuseTop = tp;
}
ptw32_threadReuseBottom = tp;
ptw32_mcs_lock_release(&node);
}
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