Initial revision

1 files changed, 940 insertions, 0 deletions

diff --git a/gc/solaris_threads.c b/gc/solaris_threads.c
new file mode 100644
index 0000000..65b2c65
--- /dev/null
+++ b/gc/solaris_threads.c
@@ -0,0 +1,940 @@
+/* 
+ * Copyright (c) 1994 by Xerox Corporation.  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 Solaris threads.  Provides functionality we wish Sun
+ * had provided.  Relies on some information we probably shouldn't rely on.
+ */
+/* Boehm, September 14, 1994 4:44 pm PDT */
+
+# if defined(SOLARIS_THREADS)
+
+# include "gc_priv.h"
+# include "solaris_threads.h"
+# include <thread.h>
+# include <synch.h>
+# include <signal.h>
+# include <fcntl.h>
+# include <sys/types.h>
+# include <sys/mman.h>
+# include <sys/time.h>
+# include <sys/resource.h>
+# include <sys/stat.h>
+# include <sys/syscall.h>
+# include <sys/procfs.h>
+# include <sys/lwp.h>
+# include <sys/reg.h>
+# define _CLASSIC_XOPEN_TYPES
+# include <unistd.h>
+# include <errno.h>
+
+/*
+ * This is the default size of the LWP arrays. If there are more LWPs
+ * than this when a stop-the-world GC happens, set_max_lwps will be
+ * called to cope.
+ * This must be higher than the number of LWPs at startup time.
+ * The threads library creates a thread early on, so the min. is 3
+ */
+# define DEFAULT_MAX_LWPS	4
+
+#undef thr_join
+#undef thr_create
+#undef thr_suspend
+#undef thr_continue
+
+cond_t GC_prom_join_cv;		/* Broadcast when any thread terminates	*/
+cond_t GC_create_cv;		/* Signalled when a new undetached	*/
+				/* thread starts.			*/
+				
+
+#ifdef MMAP_STACKS
+static int GC_zfd;
+#endif /* MMAP_STACKS */
+
+/* We use the allocation lock to protect thread-related data structures. */
+
+/* We stop the world using /proc primitives.  This makes some	*/
+/* minimal assumptions about the threads implementation.	*/
+/* We don't play by the rules, since the rules make this	*/
+/* impossible (as of Solaris 2.3).  Also note that as of	*/
+/* Solaris 2.3 the various thread and lwp suspension		*/
+/* primitives failed to stop threads by the time the request	*/
+/* is completed.						*/
+
+
+static sigset_t old_mask;
+
+/* Sleep for n milliseconds, n < 1000	*/
+void GC_msec_sleep(int n)
+{
+    struct timespec ts;
+                            
+    ts.tv_sec = 0;
+    ts.tv_nsec = 1000000*n;
+    if (syscall(SYS_nanosleep, &ts, 0) < 0) {
+	ABORT("nanosleep failed");
+    }
+}
+/* Turn off preemption;  gross but effective.  		*/
+/* Caller has allocation lock.				*/
+/* Actually this is not needed under Solaris 2.3 and	*/
+/* 2.4, but hopefully that'll change.			*/
+void preempt_off()
+{
+    sigset_t set;
+
+    (void)sigfillset(&set);
+    sigdelset(&set, SIGABRT);
+    syscall(SYS_sigprocmask, SIG_SETMASK, &set, &old_mask);
+}
+
+void preempt_on()
+{
+    syscall(SYS_sigprocmask, SIG_SETMASK, &old_mask, NULL);
+}
+
+int GC_main_proc_fd = -1;
+
+
+struct lwp_cache_entry {
+    lwpid_t lc_id;
+    int lc_descr;	/* /proc file descriptor.	*/
+}  GC_lwp_cache_default[DEFAULT_MAX_LWPS];
+
+static int max_lwps = DEFAULT_MAX_LWPS;
+static struct lwp_cache_entry *GC_lwp_cache = GC_lwp_cache_default;
+
+static prgregset_t GC_lwp_registers_default[DEFAULT_MAX_LWPS];
+static prgregset_t *GC_lwp_registers = GC_lwp_registers_default;
+
+/* Return a file descriptor for the /proc entry corresponding	*/
+/* to the given lwp.  The file descriptor may be stale if the	*/
+/* lwp exited and a new one was forked.				*/
+static int open_lwp(lwpid_t id)
+{
+    int result;
+    static int next_victim = 0;
+    register int i;
+    
+    for (i = 0; i < max_lwps; i++) {
+    	if (GC_lwp_cache[i].lc_id == id) return(GC_lwp_cache[i].lc_descr);
+    }
+    result = syscall(SYS_ioctl, GC_main_proc_fd, PIOCOPENLWP, &id);
+    /*
+     * If PIOCOPENLWP fails, try closing fds in the cache until it succeeds.
+     */
+    if (result < 0 && errno == EMFILE) {
+	    for (i = 0; i < max_lwps; i++) {
+		if (GC_lwp_cache[i].lc_id != 0) {
+        		(void)syscall(SYS_close, GC_lwp_cache[i].lc_descr);
+			result = syscall(SYS_ioctl, GC_main_proc_fd, PIOCOPENLWP, &id);
+			if (result >= 0 || (result < 0 && errno != EMFILE))
+				break;
+		}
+	    }
+    }
+    if (result < 0) {
+	if (errno == EMFILE) {
+		ABORT("Too many open files");
+	}
+        return(-1) /* exited? */;
+    }
+    if (GC_lwp_cache[next_victim].lc_id != 0)
+        (void)syscall(SYS_close, GC_lwp_cache[next_victim].lc_descr);
+    GC_lwp_cache[next_victim].lc_id = id;
+    GC_lwp_cache[next_victim].lc_descr = result;
+    if (++next_victim >= max_lwps)
+	next_victim = 0;
+    return(result);
+}
+
+static void uncache_lwp(lwpid_t id)
+{
+    register int i;
+    
+    for (i = 0; i < max_lwps; i++) {
+    	if (GC_lwp_cache[i].lc_id == id) {
+    	    (void)syscall(SYS_close, GC_lwp_cache[id].lc_descr);
+    	    GC_lwp_cache[i].lc_id = 0;
+    	    break;
+    	}
+    }
+}
+	/* Sequence of current lwp ids	*/
+static lwpid_t GC_current_ids_default[DEFAULT_MAX_LWPS + 1];
+static lwpid_t *GC_current_ids = GC_current_ids_default;
+
+	/* Temporary used below (can be big if large number of LWPs) */
+static lwpid_t last_ids_default[DEFAULT_MAX_LWPS + 1];
+static lwpid_t *last_ids = last_ids_default;
+
+
+#define ROUNDUP(n)    WORDS_TO_BYTES(ROUNDED_UP_WORDS(n))
+
+static void set_max_lwps(GC_word n)
+{
+    char *mem;
+    char *oldmem;
+    int required_bytes = ROUNDUP(n * sizeof(struct lwp_cache_entry))
+	+ ROUNDUP(n * sizeof(prgregset_t))
+	+ ROUNDUP((n + 1) * sizeof(lwpid_t))
+	+ ROUNDUP((n + 1) * sizeof(lwpid_t));
+
+    GC_expand_hp_inner(divHBLKSZ((word)required_bytes));
+    oldmem = mem = GC_scratch_alloc(required_bytes);
+    if (0 == mem) ABORT("No space for lwp data structures");
+
+    /*
+     * We can either flush the old lwp cache or copy it over. Do the latter.
+     */
+    memcpy(mem, GC_lwp_cache, max_lwps * sizeof(struct lwp_cache_entry));
+    GC_lwp_cache = (struct lwp_cache_entry*)mem;
+    mem += ROUNDUP(n * sizeof(struct lwp_cache_entry));
+
+    BZERO(GC_lwp_registers, max_lwps * sizeof(GC_lwp_registers[0]));
+    GC_lwp_registers = (prgregset_t *)mem;
+    mem += ROUNDUP(n * sizeof(prgregset_t));
+
+
+    GC_current_ids = (lwpid_t *)mem;
+    mem += ROUNDUP((n + 1) * sizeof(lwpid_t));
+
+    last_ids = (lwpid_t *)mem;
+    mem += ROUNDUP((n + 1)* sizeof(lwpid_t));
+
+    if (mem > oldmem + required_bytes)
+	ABORT("set_max_lwps buffer overflow");
+
+    max_lwps = n;
+}
+
+
+/* Stop all lwps in process.  Assumes preemption is off.	*/
+/* Caller has allocation lock (and any other locks he may	*/
+/* need).							*/
+static void stop_all_lwps()
+{
+    int lwp_fd;
+    char buf[30];
+    prstatus_t status;
+    register int i;
+    GC_bool changed;
+    lwpid_t me = _lwp_self();
+
+    if (GC_main_proc_fd == -1) {
+    	sprintf(buf, "/proc/%d", getpid());
+    	GC_main_proc_fd = syscall(SYS_open, buf, O_RDONLY);
+        if (GC_main_proc_fd < 0) {
+		if (errno == EMFILE)
+			ABORT("/proc open failed: too many open files");
+		GC_printf1("/proc open failed: errno %d", errno);
+		abort();
+        }
+    }
+    BZERO(GC_lwp_registers, sizeof (prgregset_t) * max_lwps);
+    for (i = 0; i < max_lwps; i++)
+	last_ids[i] = 0;
+    for (;;) {
+    if (syscall(SYS_ioctl, GC_main_proc_fd, PIOCSTATUS, &status) < 0)
+    	ABORT("Main PIOCSTATUS failed");
+    	if (status.pr_nlwp < 1)
+    		ABORT("Invalid number of lwps returned by PIOCSTATUS");
+    	if (status.pr_nlwp >= max_lwps) {
+    		set_max_lwps(status.pr_nlwp*2 + 10);
+		/*
+		 * The data in the old GC_current_ids and
+		 * GC_lwp_registers has been trashed. Cleaning out last_ids
+		 * will make sure every LWP gets re-examined.
+		 */
+        	for (i = 0; i < max_lwps; i++)
+			last_ids[i] = 0;
+		continue;
+    }
+        if (syscall(SYS_ioctl, GC_main_proc_fd, PIOCLWPIDS, GC_current_ids) < 0)
+            ABORT("PIOCLWPIDS failed");
+        changed = FALSE;
+        for (i = 0; GC_current_ids[i] != 0 && i < max_lwps; i++) {
+            if (GC_current_ids[i] != last_ids[i]) {
+                changed = TRUE;
+                if (GC_current_ids[i] != me) {
+		    /* PIOCSTOP doesn't work without a writable		*/
+		    /* descriptor.  And that makes the process		*/
+		    /* undebuggable.					*/
+                    if (_lwp_suspend(GC_current_ids[i]) < 0) {
+                        /* Could happen if the lwp exited */
+                        uncache_lwp(GC_current_ids[i]);
+                        GC_current_ids[i] = me; /* ignore */
+                    }
+                }
+            }
+        }
+        /*
+         * In the unlikely event something does a fork between the
+	 * PIOCSTATUS and the PIOCLWPIDS. 
+         */
+        if (i >= max_lwps)
+		continue;
+        /* All lwps in GC_current_ids != me have been suspended.  Note	*/
+        /* that _lwp_suspend is idempotent.				*/
+        for (i = 0; GC_current_ids[i] != 0; i++) {
+            if (GC_current_ids[i] != last_ids[i]) {
+                if (GC_current_ids[i] != me) {
+                    lwp_fd = open_lwp(GC_current_ids[i]);
+		    if (lwp_fd == -1)
+		    {
+			    GC_current_ids[i] = me;
+			    continue;
+		    }
+		    /* LWP should be stopped.  Empirically it sometimes	*/
+		    /* isn't, and more frequently the PR_STOPPED flag	*/
+		    /* is not set.  Wait for PR_STOPPED.		*/
+                    if (syscall(SYS_ioctl, lwp_fd,
+                                PIOCSTATUS, &status) < 0) {
+			/* Possible if the descriptor was stale, or */
+			/* we encountered the 2.3 _lwp_suspend bug. */
+			uncache_lwp(GC_current_ids[i]);
+                        GC_current_ids[i] = me; /* handle next time. */
+                    } else {
+                        while (!(status.pr_flags & PR_STOPPED)) {
+                            GC_msec_sleep(1);
+			    if (syscall(SYS_ioctl, lwp_fd,
+				    	PIOCSTATUS, &status) < 0) {
+                            	ABORT("Repeated PIOCSTATUS failed");
+			    }
+			    if (status.pr_flags & PR_STOPPED) break;
+			    
+			    GC_msec_sleep(20);
+			    if (syscall(SYS_ioctl, lwp_fd,
+				    	PIOCSTATUS, &status) < 0) {
+                            	ABORT("Repeated PIOCSTATUS failed");
+			    }
+                        }
+                        if (status.pr_who !=  GC_current_ids[i]) {
+				/* can happen if thread was on death row */
+				uncache_lwp(GC_current_ids[i]);
+				GC_current_ids[i] = me; /* handle next time. */
+				continue;	
+                        }
+                        /* Save registers where collector can */
+			/* find them.			  */
+			    BCOPY(status.pr_reg, GC_lwp_registers[i],
+				  sizeof (prgregset_t));
+                    }
+                }
+            }
+        }
+        if (!changed) break;
+        for (i = 0; i < max_lwps; i++) last_ids[i] = GC_current_ids[i];
+    }
+}
+
+/* Restart all lwps in process.  Assumes preemption is off.	*/
+static void restart_all_lwps()
+{
+    int lwp_fd;
+    register int i;
+    GC_bool changed;
+    lwpid_t me = _lwp_self();
+#   define PARANOID
+
+    for (i = 0; GC_current_ids[i] != 0; i++) {
+#	ifdef PARANOID
+	  if (GC_current_ids[i] != me) {
+	    int lwp_fd = open_lwp(GC_current_ids[i]);
+	    prstatus_t status;
+	    
+	    if (lwp_fd < 0) ABORT("open_lwp failed");
+	    if (syscall(SYS_ioctl, lwp_fd,
+			PIOCSTATUS, &status) < 0) {
+                ABORT("PIOCSTATUS failed in restart_all_lwps");
+	    }
+	    if (memcmp(status.pr_reg, GC_lwp_registers[i],
+		       sizeof (prgregset_t)) != 0) {
+		    int j;
+
+		    for(j = 0; j < NGREG; j++)
+		    {
+			    GC_printf3("%i: %x -> %x\n", j,
+				       GC_lwp_registers[i][j],
+				       status.pr_reg[j]);
+		    }
+		ABORT("Register contents changed");
+	    }
+	    if (!status.pr_flags & PR_STOPPED) {
+	    	ABORT("lwp no longer stopped");
+	    }
+#ifdef SPARC
+	    {
+		    gwindows_t windows;
+	      if (syscall(SYS_ioctl, lwp_fd,
+			PIOCGWIN, &windows) < 0) {
+                ABORT("PIOCSTATUS failed in restart_all_lwps");
+	      }
+	      if (windows.wbcnt > 0) ABORT("unsaved register windows");
+	    }
+#endif
+	  }
+#	endif /* PARANOID */
+	if (GC_current_ids[i] == me) continue;
+        if (_lwp_continue(GC_current_ids[i]) < 0) {
+            ABORT("Failed to restart lwp");
+        }
+    }
+    if (i >= max_lwps) ABORT("Too many lwps");
+}
+
+GC_bool GC_multithreaded = 0;
+
+void GC_stop_world()
+{
+    preempt_off();
+    if (GC_multithreaded)
+        stop_all_lwps();
+}
+
+void GC_start_world()
+{
+    if (GC_multithreaded)
+        restart_all_lwps();
+    preempt_on();
+}
+
+void GC_thr_init(void);
+
+GC_bool GC_thr_initialized = FALSE;
+
+size_t GC_min_stack_sz;
+
+size_t GC_page_sz;
+
+/*
+ * stack_head is stored at the top of free stacks
+ */
+struct stack_head {
+	struct stack_head	*next;
+	ptr_t			base;
+	thread_t		owner;
+};
+
+# define N_FREE_LISTS 25
+struct stack_head *GC_stack_free_lists[N_FREE_LISTS] = { 0 };
+		/* GC_stack_free_lists[i] is free list for stacks of 	*/
+		/* size GC_min_stack_sz*2**i.				*/
+		/* Free lists are linked through stack_head stored	*/			/* at top of stack.					*/
+
+/* Return a stack of size at least *stack_size.  *stack_size is	*/
+/* replaced by the actual stack size.				*/
+/* Caller holds allocation lock.				*/
+ptr_t GC_stack_alloc(size_t * stack_size)
+{
+    register size_t requested_sz = *stack_size;
+    register size_t search_sz = GC_min_stack_sz;
+    register int index = 0;	/* = log2(search_sz/GC_min_stack_sz) */
+    register ptr_t base;
+    register struct stack_head *result;
+    
+    while (search_sz < requested_sz) {
+        search_sz *= 2;
+        index++;
+    }
+    if ((result = GC_stack_free_lists[index]) == 0
+        && (result = GC_stack_free_lists[index+1]) != 0) {
+        /* Try next size up. */
+        search_sz *= 2; index++;
+    }
+    if (result != 0) {
+        base =  GC_stack_free_lists[index]->base;
+        GC_stack_free_lists[index] = GC_stack_free_lists[index]->next;
+    } else {
+#ifdef MMAP_STACKS
+        base = (ptr_t)mmap(0, search_sz + GC_page_sz,
+			     PROT_READ|PROT_WRITE, MAP_PRIVATE |MAP_NORESERVE,
+			     GC_zfd, 0);
+	if (base == (ptr_t)-1)
+	{
+		*stack_size = 0;
+		return NULL;
+	}
+
+	mprotect(base, GC_page_sz, PROT_NONE);
+	/* Should this use divHBLKSZ(search_sz + GC_page_sz) ? -- cf */
+	GC_is_fresh((struct hblk *)base, divHBLKSZ(search_sz));
+	base += GC_page_sz;
+
+#else
+        base = (ptr_t) GC_scratch_alloc(search_sz + 2*GC_page_sz);
+	if (base == NULL)
+	{
+		*stack_size = 0;
+		return NULL;
+	}
+
+        base = (ptr_t)(((word)base + GC_page_sz) & ~(GC_page_sz - 1));
+        /* Protect hottest page to detect overflow. */
+#	ifdef SOLARIS23_MPROTECT_BUG_FIXED
+            mprotect(base, GC_page_sz, PROT_NONE);
+#	endif
+        GC_is_fresh((struct hblk *)base, divHBLKSZ(search_sz));
+
+        base += GC_page_sz;
+#endif
+    }
+    *stack_size = search_sz;
+    return(base);
+}
+
+/* Caller holds  allocationlock.					*/
+void GC_stack_free(ptr_t stack, size_t size)
+{
+    register int index = 0;
+    register size_t search_sz = GC_min_stack_sz;
+    register struct stack_head *head;
+    
+#ifdef MMAP_STACKS
+    /* Zero pointers */
+    mmap(stack, size, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_NORESERVE|MAP_FIXED,
+	 GC_zfd, 0);
+#endif
+    while (search_sz < size) {
+        search_sz *= 2;
+        index++;
+    }
+    if (search_sz != size) ABORT("Bad stack size");
+
+    head = (struct stack_head *)(stack + search_sz - sizeof(struct stack_head));
+    head->next = GC_stack_free_lists[index];
+    head->base = stack;
+    GC_stack_free_lists[index] = head;
+}
+
+void GC_my_stack_limits();
+
+/* Notify virtual dirty bit implementation that known empty parts of	*/
+/* stacks do not contain useful data.					*/ 
+/* Caller holds allocation lock.					*/
+void GC_old_stacks_are_fresh()
+{
+/* No point in doing this for MMAP stacks - and pointers are zero'd out */
+/* by the mmap in GC_stack_free */
+#ifndef MMAP_STACKS
+    register int i;
+    register struct stack_head *s;
+    register ptr_t p;
+    register size_t sz;
+    register struct hblk * h;
+    int dummy;
+    
+    for (i = 0, sz= GC_min_stack_sz; i < N_FREE_LISTS;
+         i++, sz *= 2) {
+         for (s = GC_stack_free_lists[i]; s != 0; s = s->next) {
+             p = s->base;
+             h = (struct hblk *)(((word)p + HBLKSIZE-1) & ~(HBLKSIZE-1));
+             if ((ptr_t)h == p) {
+                 GC_is_fresh((struct hblk *)p, divHBLKSZ(sz));
+             } else {
+                 GC_is_fresh((struct hblk *)p, divHBLKSZ(sz) - 1);
+                 BZERO(p, (ptr_t)h - p);
+             }
+         }
+    }
+#endif /* MMAP_STACKS */
+    GC_my_stack_limits();
+}
+
+/* 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.							*/
+
+# define THREAD_TABLE_SZ 128	/* Must be power of 2	*/
+volatile GC_thread GC_threads[THREAD_TABLE_SZ];
+
+/* Add a thread to GC_threads.  We assume it wasn't already there.	*/
+/* Caller holds allocation lock.					*/
+GC_thread GC_new_thread(thread_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;
+    
+    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 -> finished = 0; */
+    (void) cond_init(&(result->join_cv), USYNC_THREAD, 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.				*/
+void GC_delete_thread(thread_t id)
+{
+    int hv = ((word)id) % THREAD_TABLE_SZ;
+    register GC_thread p = GC_threads[hv];
+    register GC_thread prev = 0;
+    
+    while (p -> id != id) {
+        prev = p;
+        p = p -> next;
+    }
+    if (prev == 0) {
+        GC_threads[hv] = p -> next;
+    } else {
+        prev -> next = p -> next;
+    }
+}
+
+/* Return the GC_thread correpsonding to a given thread_t.	*/
+/* Returns 0 if it's not there.					*/
+/* Caller holds  allocation lock.				*/
+GC_thread GC_lookup_thread(thread_t id)
+{
+    int hv = ((word)id) % THREAD_TABLE_SZ;
+    register GC_thread p = GC_threads[hv];
+    
+    while (p != 0 && p -> id != id) p = p -> next;
+    return(p);
+}
+
+# define MAX_ORIG_STACK_SIZE (8 * 1024 * 1024)
+
+word GC_get_orig_stack_size() {
+    struct rlimit rl;
+    static int warned = 0;
+    int result;
+
+    if (getrlimit(RLIMIT_STACK, &rl) != 0) ABORT("getrlimit failed");
+    result = (word)rl.rlim_cur & ~(HBLKSIZE-1);
+    if (result > MAX_ORIG_STACK_SIZE) {
+	if (!warned) {
+	    WARN("Large stack limit(%ld): only scanning 8 MB", result);
+	    warned = 1;
+	}
+	result = MAX_ORIG_STACK_SIZE;
+    }
+    return result;
+}
+
+/* Notify dirty bit implementation of unused parts of my stack. */
+/* Caller holds allocation lock.				*/
+void GC_my_stack_limits()
+{
+    int dummy;
+    register ptr_t hottest = (ptr_t)((word)(&dummy) & ~(HBLKSIZE-1));
+    register GC_thread me = GC_lookup_thread(thr_self());
+    register size_t stack_size = me -> stack_size;
+    register ptr_t stack;
+    
+    if (stack_size == 0) {
+      /* original thread */
+        /* Empirically, what should be the stack page with lowest	*/
+        /* address is actually inaccessible.				*/
+        stack_size = GC_get_orig_stack_size() - GC_page_sz;
+        stack = GC_stackbottom - stack_size + GC_page_sz;
+    } else {
+        stack = me -> stack;
+    }
+    if (stack > hottest || stack + stack_size < hottest) {
+    	ABORT("sp out of bounds");
+    }
+    GC_is_fresh((struct hblk *)stack, divHBLKSZ(hottest - stack));
+}
+
+
+/* We hold allocation lock.  We assume the world is stopped.	*/
+void GC_push_all_stacks()
+{
+    register int i;
+    register GC_thread p;
+    register ptr_t sp = GC_approx_sp();
+    register ptr_t bottom, top;
+    struct rlimit rl;
+    
+#   define PUSH(bottom,top) \
+      if (GC_dirty_maintained) { \
+	GC_push_dirty((bottom), (top), GC_page_was_ever_dirty, \
+		      GC_push_all_stack); \
+      } else { \
+        GC_push_all_stack((bottom), (top)); \
+      }
+    GC_push_all_stack((ptr_t)GC_lwp_registers,
+		      (ptr_t)GC_lwp_registers
+		      + max_lwps * sizeof(GC_lwp_registers[0]));
+    for (i = 0; i < THREAD_TABLE_SZ; i++) {
+      for (p = GC_threads[i]; p != 0; p = p -> next) {
+        if (p -> stack_size != 0) {
+            bottom = p -> stack;
+            top = p -> stack + p -> stack_size;
+        } else {
+            /* The original stack. */
+            bottom = GC_stackbottom - GC_get_orig_stack_size() + GC_page_sz;
+            top = GC_stackbottom;
+        }
+        if ((word)sp > (word)bottom && (word)sp < (word)top) bottom = sp;
+        PUSH(bottom, top);
+      }
+    }
+}
+
+
+int GC_is_thread_stack(ptr_t addr)
+{
+    register int i;
+    register GC_thread p;
+    register ptr_t bottom, top;
+    struct rlimit rl;
+    
+    for (i = 0; i < THREAD_TABLE_SZ; i++) {
+      for (p = GC_threads[i]; p != 0; p = p -> next) {
+        if (p -> stack_size != 0) {
+            if (p -> stack <= addr &&
+		addr < p -> stack + p -> stack_size)
+		    return 1;
+	}
+      }
+    }
+}
+
+/* The only thread that ever really performs a thr_join.	*/
+void * GC_thr_daemon(void * dummy)
+{
+    void *status;
+    thread_t departed;
+    register GC_thread t;
+    register int i;
+    register int result;
+    
+    for(;;) {
+      start:
+        result = thr_join((thread_t)0, &departed, &status);
+    	LOCK();
+    	if (result != 0) {
+    	    /* No more threads; wait for create. */
+    	    for (i = 0; i < THREAD_TABLE_SZ; i++) {
+    	        for (t = GC_threads[i]; t != 0; t = t -> next) {
+                    if (!(t -> flags & (DETACHED | FINISHED))) {
+                      UNLOCK();
+                      goto start; /* Thread started just before we */
+                      		  /* acquired the lock.		   */
+                    }
+                }
+            }
+            cond_wait(&GC_create_cv, &GC_allocate_ml);
+            UNLOCK();
+    	} else {
+    	    t = GC_lookup_thread(departed);
+	    GC_multithreaded--;
+    	    if (!(t -> flags & CLIENT_OWNS_STACK)) {
+    	    	GC_stack_free(t -> stack, t -> stack_size);
+    	    }
+    	    if (t -> flags & DETACHED) {
+    	    	GC_delete_thread(departed);
+    	    } else {
+    	        t -> status = status;
+    	    	t -> flags |= FINISHED;
+    	    	cond_signal(&(t -> join_cv));
+    	    	cond_broadcast(&GC_prom_join_cv);
+    	    }
+    	    UNLOCK();
+    	}
+    }
+}
+
+/* We hold the allocation lock, or caller ensures that 2 instances	*/
+/* cannot be invoked concurrently.					*/
+void GC_thr_init(void)
+{
+    GC_thread t;
+    thread_t tid;
+
+    if (GC_thr_initialized)
+	    return;
+    GC_thr_initialized = TRUE;
+    GC_min_stack_sz = ((thr_min_stack() + 32*1024 + HBLKSIZE-1)
+    		       & ~(HBLKSIZE - 1));
+    GC_page_sz = sysconf(_SC_PAGESIZE);
+#ifdef MMAP_STACKS
+    GC_zfd = open("/dev/zero", O_RDONLY);
+    if (GC_zfd == -1)
+	    ABORT("Can't open /dev/zero");
+#endif /* MMAP_STACKS */
+    cond_init(&GC_prom_join_cv, USYNC_THREAD, 0);
+    cond_init(&GC_create_cv, USYNC_THREAD, 0);
+    /* Add the initial thread, so we can stop it.	*/
+      t = GC_new_thread(thr_self());
+      t -> stack_size = 0;
+      t -> flags = DETACHED | CLIENT_OWNS_STACK;
+    if (thr_create(0 /* stack */, 0 /* stack_size */, GC_thr_daemon,
+    		   0 /* arg */, THR_DETACHED | THR_DAEMON,
+    		   &tid /* thread_id */) != 0) {
+    	ABORT("Cant fork daemon");
+    }
+    thr_setprio(tid, 126);
+}
+
+/* We acquire the allocation lock to prevent races with 	*/
+/* stopping/starting world.					*/
+/* This is no more correct than the underlying Solaris 2.X	*/
+/* implementation.  Under 2.3 THIS IS BROKEN.			*/
+int GC_thr_suspend(thread_t target_thread)
+{
+    GC_thread t;
+    int result;
+    
+    LOCK();
+    result = thr_suspend(target_thread);
+    if (result == 0) {
+    	t = GC_lookup_thread(target_thread);
+    	if (t == 0) ABORT("thread unknown to GC");
+        t -> flags |= SUSPENDED;
+    }
+    UNLOCK();
+    return(result);
+}
+
+int GC_thr_continue(thread_t target_thread)
+{
+    GC_thread t;
+    int result;
+    
+    LOCK();
+    result = thr_continue(target_thread);
+    if (result == 0) {
+    	t = GC_lookup_thread(target_thread);
+    	if (t == 0) ABORT("thread unknown to GC");
+        t -> flags &= ~SUSPENDED;
+    }
+    UNLOCK();
+    return(result);
+}
+
+int GC_thr_join(thread_t wait_for, thread_t *departed, void **status)
+{
+    register GC_thread t;
+    int result = 0;
+    
+    LOCK();
+    if (wait_for == 0) {
+        register int i;
+        register GC_bool thread_exists;
+    
+    	for (;;) {
+    	  thread_exists = FALSE;
+    	  for (i = 0; i < THREAD_TABLE_SZ; i++) {
+    	    for (t = GC_threads[i]; t != 0; t = t -> next) {
+              if (!(t -> flags & DETACHED)) {
+                if (t -> flags & FINISHED) {
+                  goto found;
+                }
+                thread_exists = TRUE;
+              }
+            }
+          }
+          if (!thread_exists) {
+              result = ESRCH;
+    	      goto out;
+          }
+          cond_wait(&GC_prom_join_cv, &GC_allocate_ml);
+        }
+    } else {
+        t = GC_lookup_thread(wait_for);
+    	if (t == 0 || t -> flags & DETACHED) {
+    	    result = ESRCH;
+    	    goto out;
+    	}
+    	if (wait_for == thr_self()) {
+    	    result = EDEADLK;
+    	    goto out;
+    	}
+    	while (!(t -> flags & FINISHED)) {
+            cond_wait(&(t -> join_cv), &GC_allocate_ml);
+    	}
+    	
+    }
+  found:
+    if (status) *status = t -> status;
+    if (departed) *departed = t -> id;
+    cond_destroy(&(t -> join_cv));
+    GC_delete_thread(t -> id);
+  out:
+    UNLOCK();
+    return(result);
+}
+
+
+int
+GC_thr_create(void *stack_base, size_t stack_size,
+              void *(*start_routine)(void *), void *arg, long flags,
+              thread_t *new_thread)
+{
+    int result;
+    GC_thread t;
+    thread_t my_new_thread;
+    word my_flags = 0;
+    void * stack = stack_base;
+   
+    LOCK();
+    if (!GC_thr_initialized)
+    {
+    GC_thr_init();
+    }
+    GC_multithreaded++;
+    if (stack == 0) {
+     	if (stack_size == 0) stack_size = GC_min_stack_sz;
+     	stack = (void *)GC_stack_alloc(&stack_size);
+     	if (stack == 0) {
+	    GC_multithreaded--;
+     	    UNLOCK();
+     	    return(ENOMEM);
+     	}
+    } else {
+    	my_flags |= CLIENT_OWNS_STACK;
+    }
+    if (flags & THR_DETACHED) my_flags |= DETACHED;
+    if (flags & THR_SUSPENDED) my_flags |= SUSPENDED;
+    result = thr_create(stack, stack_size, start_routine,
+   		        arg, flags & ~THR_DETACHED, &my_new_thread);
+    if (result == 0) {
+        t = GC_new_thread(my_new_thread);
+        t -> flags = my_flags;
+        if (!(my_flags & DETACHED)) cond_init(&(t -> join_cv), USYNC_THREAD, 0);
+        t -> stack = stack;
+        t -> stack_size = stack_size;
+        if (new_thread != 0) *new_thread = my_new_thread;
+        cond_signal(&GC_create_cv);
+    } else {
+	GC_multithreaded--;
+        if (!(my_flags & CLIENT_OWNS_STACK)) {
+      	    GC_stack_free(stack, stack_size);
+	}
+    }        
+    UNLOCK();  
+    return(result);
+}
+
+# else /* SOLARIS_THREADS */
+
+#ifndef LINT
+  int GC_no_sunOS_threads;
+#endif
+#endif