aix_irix_threads.c

A garbage collector for C and C

/* 
 * Copyright (c) 1991-1995 by Xerox Corporation.  All rights reserved.
 * Copyright (c) 1996-1999 by Silicon Graphics.  All rights reserved.
 * Copyright (c) 1999-2003 by Hewlett-Packard Company. All rights reserved.
 *
 * THIS MATERIAL IS PROVIDED AS IS, WITH ABSOLUTELY NO WARRANTY EXPRESSED
 * OR IMPLIED.  ANY USE IS AT YOUR OWN RISK.
 *
 * Permission is hereby granted to use or copy this program
 * for any purpose,  provided the above notices are retained on all copies.
 * Permission to modify the code and to distribute modified code is granted,
 * provided the above notices are retained, and a notice that the code was
 * modified is included with the above copyright notice.
 */
/*
 * Support code for Irix (>=6.2) Pthreads and for AIX pthreads.
 * This relies on properties
 * not guaranteed by the Pthread standard.  It may or may not be portable
 * to other implementations.
 *
 * Note that there is a lot of code duplication between this file and
 * (pthread_support.c, pthread_stop_world.c).  They should be merged.
 * Pthread_support.c should be directly usable.
 *
 * Please avoid adding new ports here; use the generic pthread support
 * as a base instead.
 */

# include "private/gc_priv.h"

# if defined(GC_IRIX_THREADS) || defined(GC_AIX_THREADS)

# include <pthread.h>
# include <assert.h>
# include <semaphore.h>
# include <time.h>
# include <errno.h>
# include <unistd.h>
# include <sys/mman.h>
# include <sys/time.h>

#undef pthread_create
#undef pthread_sigmask
#undef pthread_join

#if defined(GC_IRIX_THREADS) && !defined(MUTEX_RECURSIVE_NP)
#define MUTEX_RECURSIVE_NP PTHREAD_MUTEX_RECURSIVE
#endif

void GC_thr_init();

#if 0
void GC_print_sig_mask()
{
    sigset_t blocked;
    int i;

    if (pthread_sigmask(SIG_BLOCK, NULL, &blocked) != 0)
    	ABORT("pthread_sigmask");
    GC_printf0("Blocked: ");
    for (i = 1; i <= MAXSIG; i++) {
        if (sigismember(&blocked, i)) { GC_printf1("%ld ",(long) i); }
    }
    GC_printf0("\n");
}
#endif

/* We use the allocation lock to protect thread-related data structures. */

/* The set of all known threads.  We intercept thread creation and 	*/
/* joins.  We never actually create detached threads.  We allocate all 	*/
/* new thread stacks ourselves.  These allow us to maintain this	*/
/* data structure.							*/
/* Protected by GC_thr_lock.						*/
/* Some of this should be declared volatile, but that's incosnsistent	*/
/* with some library routine declarations.  		 		*/
typedef struct GC_Thread_Rep {
    struct GC_Thread_Rep * next;  /* More recently allocated threads	*/
				  /* with a given pthread id come 	*/
				  /* first.  (All but the first are	*/
				  /* guaranteed to be dead, but we may  */
				  /* not yet have registered the join.) */
    pthread_t id;
    word stop;
#	define NOT_STOPPED 0
#	define PLEASE_STOP 1
#	define STOPPED 2
    word flags;
#	define FINISHED 1   	/* Thread has exited.	*/
#	define DETACHED 2	/* Thread is intended to be detached.	*/
    ptr_t stack_cold;		/* cold end of the stack		*/
    ptr_t stack_hot;  		/* Valid only when stopped. */
				/* But must be within stack region at	*/
				/* all times.				*/
    void * status;		/* Used only to avoid premature 	*/
				/* reclamation of any data it might 	*/
				/* reference.				*/
} * GC_thread;

GC_thread GC_lookup_thread(pthread_t id);

/*
 * The only way to suspend threads given the pthread interface is to send
 * signals.  Unfortunately, this means we have to reserve
 * a signal, and intercept client calls to change the signal mask.
 */
#if 0 /* DOB: 6.1 */
# if defined(GC_AIX_THREADS)
#   define SIG_SUSPEND SIGUSR1
# else
#   define SIG_SUSPEND (SIGRTMIN + 6)
# endif
#endif

pthread_mutex_t GC_suspend_lock = PTHREAD_MUTEX_INITIALIZER;
				/* Number of threads stopped so far	*/
pthread_cond_t GC_suspend_ack_cv = PTHREAD_COND_INITIALIZER;
pthread_cond_t GC_continue_cv = PTHREAD_COND_INITIALIZER;

void GC_suspend_handler(int sig)
{
    int dummy;
    GC_thread me;
    sigset_t all_sigs;
    sigset_t old_sigs;
    int i;

    if (sig != SIG_SUSPEND) ABORT("Bad signal in suspend_handler");
    me = GC_lookup_thread(pthread_self());
    /* The lookup here is safe, since I'm doing this on behalf  */
    /* of a thread which holds the allocation lock in order	*/
    /* to stop the world.  Thus concurrent modification of the	*/
    /* data structure is impossible.				*/
    if (PLEASE_STOP != me -> stop) {
	/* Misdirected signal.	*/
	pthread_mutex_unlock(&GC_suspend_lock);
	return;
    }
    pthread_mutex_lock(&GC_suspend_lock);
    me -> stack_hot = (ptr_t)(&dummy);
    me -> stop = STOPPED;
    pthread_cond_signal(&GC_suspend_ack_cv);
    pthread_cond_wait(&GC_continue_cv, &GC_suspend_lock);
    pthread_mutex_unlock(&GC_suspend_lock);
    /* GC_printf1("Continuing 0x%x\n", pthread_self()); */
}


GC_bool GC_thr_initialized = FALSE;


# define THREAD_TABLE_SZ 128	/* Must be power of 2	*/
volatile GC_thread GC_threads[THREAD_TABLE_SZ];

void GC_push_thread_structures GC_PROTO((void))
{
    GC_push_all((ptr_t)(GC_threads), (ptr_t)(GC_threads)+sizeof(GC_threads));
}

/* Add a thread to GC_threads.  We assume it wasn't already there.	*/
/* Caller holds allocation lock.					*/
GC_thread GC_new_thread(pthread_t id)
{
    int hv = ((word)id) % THREAD_TABLE_SZ;
    GC_thread result;
    static struct GC_Thread_Rep first_thread;
    static GC_bool first_thread_used = FALSE;
    
    GC_ASSERT(I_HOLD_LOCK());
    if (!first_thread_used) {
    	result = &first_thread;
    	first_thread_used = TRUE;
    	/* Dont acquire allocation lock, since we may already hold it. */
    } else {
        result = (struct GC_Thread_Rep *)
        	 GC_generic_malloc_inner(sizeof(struct GC_Thread_Rep), NORMAL);
    }
    if (result == 0) return(0);
    result -> id = id;
    result -> next = GC_threads[hv];
    GC_threads[hv] = result;
    /* result -> flags = 0;     */
    /* result -> stop = 0;	*/
    return(result);
}

/* Delete a thread from GC_threads.  We assume it is there.	*/
/* (The code intentionally traps if it wasn't.)			*/
/* Caller holds allocation lock.				*/
/* We explicitly pass in the GC_thread we're looking for, since */
/* if a thread has been joined, but we have not yet		*/
/* been notified, then there may be more than one thread 	*/
/* in the table with the same pthread id.			*/
/* This is OK, but we need a way to delete a specific one.	*/
void GC_delete_gc_thread(pthread_t id, GC_thread gc_id)
{
    int hv = ((word)id) % THREAD_TABLE_SZ;
    register GC_thread p = GC_threads[hv];
    register GC_thread prev = 0;

    GC_ASSERT(I_HOLD_LOCK());
    while (p != gc_id) {
        prev = p;
        p = p -> next;
    }
    if (prev == 0) {
        GC_threads[hv] = p -> next;
    } else {
        prev -> next = p -> next;
    }
}

/* Return a GC_thread corresponding to a given thread_t.	*/
/* Returns 0 if it's not there.					*/
/* Caller holds  allocation lock or otherwise inhibits 		*/
/* updates.							*/
/* If there is more than one thread with the given id we 	*/
/* return the most recent one.					*/
GC_thread GC_lookup_thread(pthread_t id)
{
    int hv = ((word)id) % THREAD_TABLE_SZ;
    register GC_thread p = GC_threads[hv];
    
    /* I either hold the lock, or i'm being called from the stop-the-world
     * handler. */
#if defined(GC_AIX_THREADS)
    GC_ASSERT(I_HOLD_LOCK()); /* no stop-the-world handler needed on AIX */
#endif
    while (p != 0 && !pthread_equal(p -> id, id)) p = p -> next;
    return(p);
}

#if defined(GC_AIX_THREADS)
void GC_stop_world()
{
    pthread_t my_thread = pthread_self();
    register int i;
    register GC_thread p;
    register int result;
    struct timespec timeout;

    GC_ASSERT(I_HOLD_LOCK());
    for (i = 0; i < THREAD_TABLE_SZ; i++) {
      for (p = GC_threads[i]; p != 0; p = p -> next) {
        if (p -> id != my_thread) {
          pthread_suspend_np(p->id);
        }
      }
    }
    /* GC_printf1("World stopped 0x%x\n", pthread_self()); */
}

void GC_start_world()
{
    GC_thread p;
    unsigned i;
    pthread_t my_thread = pthread_self();

    /* GC_printf0("World starting\n"); */
    GC_ASSERT(I_HOLD_LOCK());
    for (i = 0; i < THREAD_TABLE_SZ; i++) {
      for (p = GC_threads[i]; p != 0; p = p -> next) {
        if (p -> id != my_thread) {
          pthread_continue_np(p->id);
        }
      }
    }
}

#else /* GC_AIX_THREADS */

/* Caller holds allocation lock.	*/
void GC_stop_world()
{
    pthread_t my_thread = pthread_self();
    register int i;
    register GC_thread p;
    register int result;
    struct timespec timeout;
    
    GC_ASSERT(I_HOLD_LOCK());
    for (i = 0; i < THREAD_TABLE_SZ; i++) {
      for (p = GC_threads[i]; p != 0; p = p -> next) {
        if (p -> id != my_thread) {
            if (p -> flags & FINISHED) {
		p -> stop = STOPPED;
		continue;
	    }
	    p -> stop = PLEASE_STOP;
            result = pthread_kill(p -> id, SIG_SUSPEND);
	    /* GC_printf1("Sent signal to 0x%x\n", p -> id); */
	    switch(result) {
                case ESRCH:
                    /* Not really there anymore.  Possible? */
                    p -> stop = STOPPED;
                    break;
                case 0:
                    break;
                default:
                    ABORT("pthread_kill failed");
            }
        }
      }
    }
    pthread_mutex_lock(&GC_suspend_lock);
    for (i = 0; i < THREAD_TABLE_SZ; i++) {
      for (p = GC_threads[i]; p != 0; p = p -> next) {
        while (p -> id != my_thread && p -> stop != STOPPED) {
	    clock_gettime(CLOCK_REALTIME, &timeout);
            timeout.tv_nsec += 50000000; /* 50 msecs */
            if (timeout.tv_nsec >= 1000000000) {
                timeout.tv_nsec -= 1000000000;
                ++timeout.tv_sec;
            }
            result = pthread_cond_timedwait(&GC_suspend_ack_cv,
					    &GC_suspend_lock,
                                            &timeout);
            if (result == ETIMEDOUT) {
                /* Signal was lost or misdirected.  Try again.      */
                /* Duplicate signals should be benign.              */
                result = pthread_kill(p -> id, SIG_SUSPEND);
	    }
	}
      }
    }
    pthread_mutex_unlock(&GC_suspend_lock);
    /* GC_printf1("World stopped 0x%x\n", pthread_self()); */
}

/* Caller holds allocation lock.	*/
void GC_start_world()
{
    GC_thread p;
    unsigned i;

    /* GC_printf0("World starting\n"); */
    GC_ASSERT(I_HOLD_LOCK());
    for (i = 0; i < THREAD_TABLE_SZ; i++) {
      for (p = GC_threads[i]; p != 0; p = p -> next) {
	p -> stop = NOT_STOPPED;
      }
    }
    pthread_mutex_lock(&GC_suspend_lock);
    /* All other threads are at pthread_cond_wait in signal handler.	*/
    /* Otherwise we couldn't have acquired the lock.			*/