/* * Copyright (c) 1998 John Birrell * All rights reserved. * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: * 1. Redistributions of source code must retain the above copyright * notice, this list of conditions and the following disclaimer. * 2. Redistributions in binary form must reproduce the above copyright * notice, this list of conditions and the following disclaimer in the * documentation and/or other materials provided with the distribution. * 3. All advertising materials mentioning features or use of this software * must display the following acknowledgement: * This product includes software developed by John Birrell. * 4. Neither the name of the author nor the names of any co-contributors * may be used to endorse or promote products derived from this software * without specific prior written permission. * * THIS SOFTWARE IS PROVIDED BY JOHN BIRRELL AND CONTRIBUTORS ``AS IS'' AND * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF * SUCH DAMAGE. * * $FreeBSD: uthread_gc.c,v 1.2 1998/09/30 19:17:51 dt Exp $ * $OpenBSD: uthread_gc.c,v 1.4 1999/02/01 08:24:42 d Exp $ * * Garbage collector thread. Frees memory allocated for dead threads. * */ #include #include #include #include #include #include #ifdef _THREAD_SAFE #include #include #include "pthread_private.h" pthread_addr_t _thread_gc(pthread_addr_t arg) { int f_debug; int f_done = 0; int ret; pthread_t pthread; pthread_t pthread_cln; pthread_t pthread_nxt; pthread_t pthread_prv; struct timespec abstime; void *p_stack; sigset_t ss; /* Don't handle signals in this thread */ sigfillset(&ss); if (ret = pthread_sigmask(SIG_BLOCK, &ss, NULL)) PANIC("Can't block signals in GC thread"); /* Set a debug flag based on an environment variable. */ f_debug = (getenv("LIBC_R_DEBUG") != NULL); /* Set the name of this thread. */ pthread_set_name_np(_thread_run, "GC"); while (!f_done) { /* Check if debugging this application. */ if (f_debug) /* Dump thread info to file. */ _thread_dump_info(); /* Lock the thread list: */ _lock_thread_list(); /* Check if this is the last running thread: */ if (_thread_link_list == _thread_run && _thread_link_list->nxt == NULL) /* * This is the last thread, so it can exit * now. */ f_done = 1; /* Unlock the thread list: */ _unlock_thread_list(); /* * Lock the garbage collector mutex which ensures that * this thread sees another thread exit: */ if (pthread_mutex_lock(&_gc_mutex) != 0) PANIC("Cannot lock gc mutex"); /* No stack of thread structure to free yet: */ p_stack = NULL; pthread_cln = NULL; /* Point to the first dead thread (if there are any): */ pthread = _thread_dead; /* There is no previous dead thread: */ pthread_prv = NULL; /* * Enter a loop to search for the first dead thread that * has memory to free. */ while (p_stack == NULL && pthread_cln == NULL && pthread != NULL) { /* Save a pointer to the next thread: */ pthread_nxt = pthread->nxt_dead; /* Check if the initial thread: */ if (pthread == _thread_initial) /* Don't destroy the initial thread. */ pthread_prv = pthread; /* * Check if this thread has detached: */ else if ((pthread->attr.flags & PTHREAD_DETACHED) != 0) { /* * Check if there is no previous dead * thread: */ if (pthread_prv == NULL) /* * The dead thread is at the head * of the list: */ _thread_dead = pthread_nxt; else /* * The dead thread is not at the * head of the list: */ pthread_prv->nxt_dead = pthread->nxt_dead; /* * Check if the stack was not specified by * the caller to pthread_create and has not * been destroyed yet: */ if (pthread->attr.stackaddr_attr == NULL && pthread->stack != NULL) { /* * Point to the stack that must * be freed outside the locks: */ p_stack = pthread->stack; } /* * Point to the thread structure that must * be freed outside the locks: */ pthread_cln = pthread; } else { /* * This thread has not detached, so do * not destroy it: */ pthread_prv = pthread; /* * Check if the stack was not specified by * the caller to pthread_create and has not * been destroyed yet: */ if (pthread->attr.stackaddr_attr == NULL && pthread->stack != NULL) { /* * Point to the stack that must * be freed outside the locks: */ p_stack = pthread->stack; /* * NULL the stack pointer now * that the memory has been freed: */ pthread->stack = NULL; } } /* Point to the next thread: */ pthread = pthread_nxt; } /* * Check if this is not the last thread and there is no * memory to free this time around. */ if (!f_done && p_stack == NULL && pthread_cln == NULL) { /* Get the current time. */ if (clock_gettime(CLOCK_REALTIME,&abstime) != 0) PANIC("gc cannot get time"); /* * Do a backup poll in 10 seconds if no threads * die before then. */ abstime.tv_sec += 10; /* * Wait for a signal from a dying thread or a * timeout (for a backup poll). */ if ((ret = pthread_cond_timedwait(&_gc_cond, &_gc_mutex, &abstime)) != 0 && ret != ETIMEDOUT) PANIC("gc cannot wait for a signal"); } /* Unlock the garbage collector mutex: */ if (pthread_mutex_unlock(&_gc_mutex) != 0) PANIC("Cannot unlock gc mutex"); /* * If there is memory to free, do it now. The call to * free() might block, so this must be done outside the * locks. */ if (p_stack != NULL) free(p_stack); if (pthread_cln != NULL) { /* Lock the thread list: */ _lock_thread_list(); /* * Check if the thread is at the head of the * linked list. */ if (_thread_link_list == pthread_cln) /* There is no previous thread: */ _thread_link_list = pthread_cln->nxt; else { /* Point to the first thread in the list: */ pthread = _thread_link_list; /* * Enter a loop to find the thread in the * linked list before the thread that is * about to be freed. */ while (pthread != NULL && pthread->nxt != pthread_cln) /* Point to the next thread: */ pthread = pthread->nxt; /* Check that a previous thread was found: */ if (pthread != NULL) { /* * Point the previous thread to * the one after the thread being * freed: */ pthread->nxt = pthread_cln->nxt; } } /* Unlock the thread list: */ _unlock_thread_list(); /* Free memory allocated for the thread's name: */ if (pthread_cln->name != NULL) free(pthread_cln->name); /* * Free the memory allocated for the thread * structure. */ free(pthread_cln); } } return (NULL); } #endif /* _THREAD_SAFE */