1.0.2.7: Darwin/MacOS threading improvements
[sbcl.git] / src / runtime / thread.c
index c0166d0..9871f9f 100644 (file)
@@ -1,12 +1,39 @@
+/*
+ * This software is part of the SBCL system. See the README file for
+ * more information.
+ *
+ * This software is derived from the CMU CL system, which was
+ * written at Carnegie Mellon University and released into the
+ * public domain. The software is in the public domain and is
+ * provided with absolutely no warranty. See the COPYING and CREDITS
+ * files for more information.
+ */
+
+#include "sbcl.h"
+
 #include <stdlib.h>
 #include <stdio.h>
+#include <string.h>
+#ifndef LISP_FEATURE_WIN32
 #include <sched.h>
+#endif
 #include <signal.h>
 #include <stddef.h>
 #include <errno.h>
+#include <sys/types.h>
+#ifndef LISP_FEATURE_WIN32
+#include <sys/wait.h>
+#endif
+
+#ifdef LISP_FEATURE_MACH_EXCEPTION_HANDLER
+#include <mach/mach.h>
+#include <mach/mach_error.h>
+#include <mach/mach_types.h>
+#endif
+
 #include "runtime.h"
-#include "sbcl.h"
-#include "validate.h"          /* for CONTROL_STACK_SIZE etc */
+#include "validate.h"           /* for CONTROL_STACK_SIZE etc */
+#include "alloc.h"
 #include "thread.h"
 #include "arch.h"
 #include "target-arch-os.h"
 #include "globals.h"
 #include "dynbind.h"
 #include "genesis/cons.h"
+#include "genesis/fdefn.h"
+#include "interr.h"             /* for lose() */
+#include "gc-internal.h"
+
+#ifdef LISP_FEATURE_WIN32
+/*
+ * Win32 doesn't have SIGSTKSZ, and we're not switching stacks anyway,
+ * so define it arbitrarily
+ */
+#define SIGSTKSZ 1024
+#endif
+
+#if defined(LISP_FEATURE_DARWIN) && defined(LISP_FEATURE_SB_THREAD)
+#define QUEUE_FREEABLE_THREAD_STACKS
+#define LOCK_CREATE_THREAD
+#endif
+
+#ifdef LISP_FEATURE_FREEBSD
+#define CREATE_CLEANUP_THREAD
+#define LOCK_CREATE_THREAD
+#endif
+
 #define ALIEN_STACK_SIZE (1*1024*1024) /* 1Mb size chosen at random */
 
-int dynamic_values_bytes=4096*sizeof(lispobj); /* same for all threads */
-struct thread *all_threads;
-volatile lispobj all_threads_lock;
-volatile int countdown_to_gc;
+struct freeable_stack {
+#ifdef QUEUE_FREEABLE_THREAD_STACKS
+    struct freeable_stack *next;
+#endif
+    os_thread_t os_thread;
+    os_vm_address_t stack;
+};
+
+
+#ifdef QUEUE_FREEABLE_THREAD_STACKS
+static struct freeable_stack * volatile freeable_stack_queue = 0;
+static int freeable_stack_count = 0;
+pthread_mutex_t freeable_stack_lock = PTHREAD_MUTEX_INITIALIZER;
+#else
+static struct freeable_stack * volatile freeable_stack = 0;
+#endif
+
+int dynamic_values_bytes=4096*sizeof(lispobj);  /* same for all threads */
+struct thread * volatile all_threads;
 extern struct interrupt_data * global_interrupt_data;
 
-void get_spinlock(lispobj *word,int value);
+#ifdef LISP_FEATURE_SB_THREAD
+pthread_mutex_t all_threads_lock = PTHREAD_MUTEX_INITIALIZER;
+#ifdef LOCK_CREATE_THREAD
+static pthread_mutex_t create_thread_lock = PTHREAD_MUTEX_INITIALIZER;
+#endif
+#endif
 
-/* this is the first thing that clone() runs in the child (which is
- * why the silly calling convention).  Basically it calls the user's
- * requested lisp function after doing arch_os_thread_init and
- * whatever other bookkeeping needs to be done
- */
+#if defined(LISP_FEATURE_X86) || defined(LISP_FEATURE_X86_64)
+extern lispobj call_into_lisp_first_time(lispobj fun, lispobj *args, int nargs);
+#endif
+
+static void
+link_thread(struct thread *th)
+{
+    if (all_threads) all_threads->prev=th;
+    th->next=all_threads;
+    th->prev=0;
+    all_threads=th;
+}
 
-/* set go to 0 to stop the thread before it starts.  Convenient if you
-* want to attach a debugger to it before it does anything */
-volatile int go=1;             
+#ifdef LISP_FEATURE_SB_THREAD
+static void
+unlink_thread(struct thread *th)
+{
+    if (th->prev)
+        th->prev->next = th->next;
+    else
+        all_threads = th->next;
+    if (th->next)
+        th->next->prev = th->prev;
+}
+#endif
 
-int
-new_thread_trampoline(struct thread *th)
+static int
+initial_thread_trampoline(struct thread *th)
 {
     lispobj function;
+#if defined(LISP_FEATURE_X86) || defined(LISP_FEATURE_X86_64)
     lispobj *args = NULL;
-    function = th->unbound_marker;
-    if(go==0) {
-       fprintf(stderr, "/pausing 0x%lx(%d,%d) before new_thread_trampoline(0x%lx)\n",
-               (unsigned long)th,th->pid,getpid(),(unsigned long)function);
-       while(go==0) ;
-       fprintf(stderr, "/continue\n");
-    }
-    th->unbound_marker = UNBOUND_MARKER_WIDETAG;
-    if(arch_os_thread_init(th)==0) 
-       return 1;               /* failure.  no, really */
-#ifdef LISP_FEATURE_SB_THREAD
-    /* wait here until our thread is linked into all_threads: see below */
-    while(th->pid<1) sched_yield();
-#else
-    if(th->pid < 1)
-       lose("th->pid not set up right");
+#endif
+    function = th->no_tls_value_marker;
+    th->no_tls_value_marker = NO_TLS_VALUE_MARKER_WIDETAG;
+    if(arch_os_thread_init(th)==0) return 1;
+    link_thread(th);
+    th->os_thread=thread_self();
+#ifndef LISP_FEATURE_WIN32
+    protect_control_stack_guard_page(1);
 #endif
 
-    th->state=STATE_RUNNING;
-#if !defined(LISP_FEATURE_SB_THREAD) && defined(LISP_FEATURE_X86)
+#if defined(LISP_FEATURE_X86) || defined(LISP_FEATURE_X86_64)
     return call_into_lisp_first_time(function,args,0);
 #else
     return funcall0(function);
 #endif
 }
 
+#define THREAD_STRUCT_SIZE (THREAD_CONTROL_STACK_SIZE + BINDING_STACK_SIZE + \
+                            ALIEN_STACK_SIZE + dynamic_values_bytes + \
+                            32 * SIGSTKSZ)
+
+#ifdef LISP_FEATURE_SB_THREAD
+
+#ifdef QUEUE_FREEABLE_THREAD_STACKS
+
+static void
+queue_freeable_thread_stack(struct thread *thread_to_be_cleaned_up)
+{
+     if (thread_to_be_cleaned_up) {
+        pthread_mutex_lock(&freeable_stack_lock);
+        if (freeable_stack_queue) {
+            struct freeable_stack *new_freeable_stack = 0, *next;
+            next = freeable_stack_queue;
+            while (next->next) {
+                next = next->next;
+            }
+            new_freeable_stack = (struct freeable_stack *)
+                os_validate(0, sizeof(struct freeable_stack));
+            new_freeable_stack->next = NULL;
+            new_freeable_stack->os_thread = thread_to_be_cleaned_up->os_thread;
+            new_freeable_stack->stack = (os_vm_address_t)
+                thread_to_be_cleaned_up->control_stack_start;
+            next->next = new_freeable_stack;
+            freeable_stack_count++;
+        } else {
+            struct freeable_stack *new_freeable_stack = 0;
+            new_freeable_stack = (struct freeable_stack *)
+                os_validate(0, sizeof(struct freeable_stack));
+            new_freeable_stack->next = NULL;
+            new_freeable_stack->os_thread = thread_to_be_cleaned_up->os_thread;
+            new_freeable_stack->stack = (os_vm_address_t)
+                thread_to_be_cleaned_up->control_stack_start;
+            freeable_stack_queue = new_freeable_stack;
+            freeable_stack_count++;
+        }
+        pthread_mutex_unlock(&freeable_stack_lock);
+    }
+}
+
+#define FREEABLE_STACK_QUEUE_SIZE 4
+
+static void
+free_freeable_stacks() {
+    if (freeable_stack_queue && (freeable_stack_count > FREEABLE_STACK_QUEUE_SIZE)) {
+        struct freeable_stack* old;
+        pthread_mutex_lock(&freeable_stack_lock);
+        old = freeable_stack_queue;
+        freeable_stack_queue = old->next;
+        freeable_stack_count--;
+        gc_assert(pthread_join(old->os_thread, NULL) == 0);
+        FSHOW((stderr, "freeing thread %x stack\n", old->os_thread));
+        os_invalidate(old->stack, THREAD_STRUCT_SIZE);
+        os_invalidate((os_vm_address_t)old, sizeof(struct freeable_stack));
+        pthread_mutex_unlock(&freeable_stack_lock);
+    }
+}
+
+#elif defined(CREATE_CLEANUP_THREAD)
+static void *
+cleanup_thread(void *arg)
+{
+    struct freeable_stack *freeable = arg;
+    pthread_t self = pthread_self();
+
+    FSHOW((stderr, "/cleaner thread(%p): joining %p\n",
+           self, freeable->os_thread));
+    gc_assert(pthread_join(freeable->os_thread, NULL) == 0);
+    FSHOW((stderr, "/cleaner thread(%p): free stack %p\n",
+           self, freeable->stack));
+    os_invalidate(freeable->stack, THREAD_STRUCT_SIZE);
+    free(freeable);
+
+    pthread_detach(self);
+
+    return NULL;
+}
+
+static void
+create_cleanup_thread(struct thread *thread_to_be_cleaned_up)
+{
+    pthread_t thread;
+    int result;
+
+    if (thread_to_be_cleaned_up) {
+        struct freeable_stack *freeable =
+            malloc(sizeof(struct freeable_stack));
+        gc_assert(freeable != NULL);
+        freeable->os_thread = thread_to_be_cleaned_up->os_thread;
+        freeable->stack =
+            (os_vm_address_t) thread_to_be_cleaned_up->control_stack_start;
+        result = pthread_create(&thread, NULL, cleanup_thread, freeable);
+        gc_assert(result == 0);
+        sched_yield();
+    }
+}
+
+#else
+static void
+free_thread_stack_later(struct thread *thread_to_be_cleaned_up)
+{
+    struct freeable_stack *new_freeable_stack = 0;
+    if (thread_to_be_cleaned_up) {
+        new_freeable_stack = (struct freeable_stack *)
+            os_validate(0, sizeof(struct freeable_stack));
+        new_freeable_stack->os_thread = thread_to_be_cleaned_up->os_thread;
+        new_freeable_stack->stack = (os_vm_address_t)
+            thread_to_be_cleaned_up->control_stack_start;
+    }
+    new_freeable_stack = (struct freeable_stack *)
+        swap_lispobjs((lispobj *)(void *)&freeable_stack,
+                      (lispobj)new_freeable_stack);
+    if (new_freeable_stack) {
+        FSHOW((stderr,"/reaping %p\n", (void*) new_freeable_stack->os_thread));
+        /* Under NPTL pthread_join really waits until the thread
+         * exists and the stack can be safely freed. This is sadly not
+         * mandated by the pthread spec. */
+        gc_assert(pthread_join(new_freeable_stack->os_thread, NULL) == 0);
+        os_invalidate(new_freeable_stack->stack, THREAD_STRUCT_SIZE);
+        os_invalidate((os_vm_address_t) new_freeable_stack,
+                      sizeof(struct freeable_stack));
+    }
+}
+#endif
+
+/* this is the first thing that runs in the child (which is why the
+ * silly calling convention).  Basically it calls the user's requested
+ * lisp function after doing arch_os_thread_init and whatever other
+ * bookkeeping needs to be done
+ */
+int
+new_thread_trampoline(struct thread *th)
+{
+    lispobj function;
+    int result, lock_ret;
+
+    FSHOW((stderr,"/creating thread %lu\n", thread_self()));
+    function = th->no_tls_value_marker;
+    th->no_tls_value_marker = NO_TLS_VALUE_MARKER_WIDETAG;
+    if(arch_os_thread_init(th)==0) {
+        /* FIXME: handle error */
+        lose("arch_os_thread_init failed\n");
+    }
+
+    th->os_thread=thread_self();
+    protect_control_stack_guard_page(1);
+    /* Since GC can only know about this thread from the all_threads
+     * list and we're just adding this thread to it there is no danger
+     * of deadlocking even with SIG_STOP_FOR_GC blocked (which it is
+     * not). */
+    lock_ret = pthread_mutex_lock(&all_threads_lock);
+    gc_assert(lock_ret == 0);
+    link_thread(th);
+    lock_ret = pthread_mutex_unlock(&all_threads_lock);
+    gc_assert(lock_ret == 0);
+
+    result = funcall0(function);
+
+    /* Block GC */
+    block_blockable_signals();
+    th->state=STATE_DEAD;
+
+    /* SIG_STOP_FOR_GC is blocked and GC might be waiting for this
+     * thread, but since we are already dead it won't wait long. */
+    lock_ret = pthread_mutex_lock(&all_threads_lock);
+    gc_assert(lock_ret == 0);
+
+    gc_alloc_update_page_tables(0, &th->alloc_region);
+    unlink_thread(th);
+    pthread_mutex_unlock(&all_threads_lock);
+    gc_assert(lock_ret == 0);
+
+    if(th->tls_cookie>=0) arch_os_thread_cleanup(th);
+    os_invalidate((os_vm_address_t)th->interrupt_data,
+                  (sizeof (struct interrupt_data)));
+
+#ifdef LISP_FEATURE_MACH_EXCEPTION_HANDLER
+    FSHOW((stderr, "Deallocating mach port %x\n", THREAD_STRUCT_TO_EXCEPTION_PORT(th)));
+    mach_port_move_member(mach_task_self(),
+                          THREAD_STRUCT_TO_EXCEPTION_PORT(th),
+                          MACH_PORT_NULL);
+    mach_port_deallocate(mach_task_self(),
+                         THREAD_STRUCT_TO_EXCEPTION_PORT(th));
+    mach_port_destroy(mach_task_self(),
+                      THREAD_STRUCT_TO_EXCEPTION_PORT(th));
+#endif
+
+#ifdef QUEUE_FREEABLE_THREAD_STACKS
+    queue_freeable_thread_stack(th);
+#elif defined(CREATE_CLEANUP_THREAD)
+    create_cleanup_thread(th);
+#else
+    free_thread_stack_later(th);
+#endif
+
+    FSHOW((stderr,"/exiting thread %p\n", thread_self()));
+    return result;
+}
+
+#endif /* LISP_FEATURE_SB_THREAD */
+
+static void
+free_thread_struct(struct thread *th)
+{
+    if (th->interrupt_data)
+        os_invalidate((os_vm_address_t) th->interrupt_data,
+                      (sizeof (struct interrupt_data)));
+    os_invalidate((os_vm_address_t) th->control_stack_start,
+                  THREAD_STRUCT_SIZE);
+}
+
 /* this is called from any other thread to create the new one, and
- * initialize all parts of it that can be initialized from another 
- * thread 
+ * initialize all parts of it that can be initialized from another
+ * thread
  */
 
-pid_t create_thread(lispobj initial_function) {
+static struct thread *
+create_thread_struct(lispobj initial_function) {
     union per_thread_data *per_thread;
-    struct thread *th=0;       /*  subdue gcc */
+    struct thread *th=0;        /*  subdue gcc */
     void *spaces=0;
-    pid_t kid_pid;
+#ifdef LISP_FEATURE_SB_THREAD
+    int i;
+#endif
 
+#ifdef CREATE_CLEANUP_THREAD
+    /* Give a chance for cleanup threads to run. */
+    sched_yield();
+#endif
     /* may as well allocate all the spaces at once: it saves us from
      * having to decide what to do if only some of the allocations
      * succeed */
-    spaces=os_validate(0,
-                      THREAD_CONTROL_STACK_SIZE+
-                      BINDING_STACK_SIZE+
-                      ALIEN_STACK_SIZE+
-                      dynamic_values_bytes+
-                      32*SIGSTKSZ
-                      );
-    if(!spaces) goto cleanup;
+    spaces=os_validate(0, THREAD_STRUCT_SIZE);
+    if(!spaces)
+         return NULL;
     per_thread=(union per_thread_data *)
-       (spaces+
-        THREAD_CONTROL_STACK_SIZE+
-        BINDING_STACK_SIZE+
-        ALIEN_STACK_SIZE);
+        (spaces+
+         THREAD_CONTROL_STACK_SIZE+
+         BINDING_STACK_SIZE+
+         ALIEN_STACK_SIZE);
 
-    th=&per_thread->thread;
-    if(all_threads) {
-       memcpy(per_thread,arch_os_get_current_thread(),
-              dynamic_values_bytes);
-    } else {
 #ifdef LISP_FEATURE_SB_THREAD
-       int i;
-       for(i=0;i<(dynamic_values_bytes/sizeof(lispobj));i++)
-           per_thread->dynamic_values[i]=UNBOUND_MARKER_WIDETAG;
-       if(SymbolValue(FREE_TLS_INDEX,0)==UNBOUND_MARKER_WIDETAG) 
-           SetSymbolValue
-               (FREE_TLS_INDEX,
-                make_fixnum(MAX_INTERRUPTS+
-                            sizeof(struct thread)/sizeof(lispobj)),
-                0);
+    for(i = 0; i < (dynamic_values_bytes / sizeof(lispobj)); i++)
+        per_thread->dynamic_values[i] = NO_TLS_VALUE_MARKER_WIDETAG;
+    if (all_threads == 0) {
+        if(SymbolValue(FREE_TLS_INDEX,0)==UNBOUND_MARKER_WIDETAG) {
+            SetSymbolValue
+                (FREE_TLS_INDEX,
+                 /* FIXME: should be MAX_INTERRUPTS -1 ? */
+                 make_fixnum(MAX_INTERRUPTS+
+                             sizeof(struct thread)/sizeof(lispobj)),
+                 0);
+            SetSymbolValue(TLS_INDEX_LOCK,make_fixnum(0),0);
+        }
 #define STATIC_TLS_INIT(sym,field) \
   ((struct symbol *)(sym-OTHER_POINTER_LOWTAG))->tls_index= \
   make_fixnum(THREAD_SLOT_OFFSET_WORDS(field))
-                                 
-       STATIC_TLS_INIT(BINDING_STACK_START,binding_stack_start);
-       STATIC_TLS_INIT(BINDING_STACK_POINTER,binding_stack_pointer);
-       STATIC_TLS_INIT(CONTROL_STACK_START,control_stack_start);
-       STATIC_TLS_INIT(CONTROL_STACK_END,control_stack_end);
-       STATIC_TLS_INIT(ALIEN_STACK,alien_stack_pointer);
-#ifdef LISP_FEATURE_X86
-       STATIC_TLS_INIT(PSEUDO_ATOMIC_ATOMIC,pseudo_atomic_atomic);
-       STATIC_TLS_INIT(PSEUDO_ATOMIC_INTERRUPTED,pseudo_atomic_interrupted);
+
+        STATIC_TLS_INIT(BINDING_STACK_START,binding_stack_start);
+        STATIC_TLS_INIT(BINDING_STACK_POINTER,binding_stack_pointer);
+        STATIC_TLS_INIT(CONTROL_STACK_START,control_stack_start);
+        STATIC_TLS_INIT(CONTROL_STACK_END,control_stack_end);
+        STATIC_TLS_INIT(ALIEN_STACK,alien_stack_pointer);
+#if defined(LISP_FEATURE_X86) || defined (LISP_FEATURE_X86_64)
+        STATIC_TLS_INIT(PSEUDO_ATOMIC_BITS,pseudo_atomic_bits);
 #endif
 #undef STATIC_TLS_INIT
-#endif
     }
+#endif
 
+    th=&per_thread->thread;
     th->control_stack_start = spaces;
     th->binding_stack_start=
-       (lispobj*)((void*)th->control_stack_start+THREAD_CONTROL_STACK_SIZE);
+        (lispobj*)((void*)th->control_stack_start+THREAD_CONTROL_STACK_SIZE);
     th->control_stack_end = th->binding_stack_start;
     th->alien_stack_start=
-       (lispobj*)((void*)th->binding_stack_start+BINDING_STACK_SIZE);
+        (lispobj*)((void*)th->binding_stack_start+BINDING_STACK_SIZE);
     th->binding_stack_pointer=th->binding_stack_start;
     th->this=th;
-    th->pid=0;
-    th->state=STATE_STOPPED;
+    th->os_thread=0;
+    th->state=STATE_RUNNING;
 #ifdef LISP_FEATURE_STACK_GROWS_DOWNWARD_NOT_UPWARD
     th->alien_stack_pointer=((void *)th->alien_stack_start
-                            + ALIEN_STACK_SIZE-4); /* naked 4.  FIXME */
+                             + ALIEN_STACK_SIZE-N_WORD_BYTES);
 #else
     th->alien_stack_pointer=((void *)th->alien_stack_start);
 #endif
-#ifdef LISP_FEATURE_X86
-    th->pseudo_atomic_interrupted=0;
-    th->pseudo_atomic_atomic=0;
+#if defined(LISP_FEATURE_X86) || defined (LISP_FEATURE_X86_64)
+    th->pseudo_atomic_bits=0;
 #endif
 #ifdef LISP_FEATURE_GENCGC
     gc_set_region_empty(&th->alloc_region);
@@ -152,206 +441,286 @@ pid_t create_thread(lispobj initial_function) {
 #ifndef LISP_FEATURE_SB_THREAD
     /* the tls-points-into-struct-thread trick is only good for threaded
      * sbcl, because unithread sbcl doesn't have tls.  So, we copy the
-     * appropriate values from struct thread here, and make sure that 
+     * appropriate values from struct thread here, and make sure that
      * we use the appropriate SymbolValue macros to access any of the
      * variable quantities from the C runtime.  It's not quite OAOOM,
      * it just feels like it */
-    SetSymbolValue(BINDING_STACK_START,th->binding_stack_start,th);
-    SetSymbolValue(CONTROL_STACK_START,th->control_stack_start,th);
-    SetSymbolValue(CONTROL_STACK_END,th->control_stack_end,th);
-#ifdef LISP_FEATURE_X86
-    SetSymbolValue(BINDING_STACK_POINTER,th->binding_stack_pointer,th);
-    SetSymbolValue(ALIEN_STACK,th->alien_stack_pointer,th);
-    SetSymbolValue(PSEUDO_ATOMIC_ATOMIC,th->pseudo_atomic_atomic,th);
-    SetSymbolValue(PSEUDO_ATOMIC_INTERRUPTED,th->pseudo_atomic_interrupted,th);
+    SetSymbolValue(BINDING_STACK_START,(lispobj)th->binding_stack_start,th);
+    SetSymbolValue(CONTROL_STACK_START,(lispobj)th->control_stack_start,th);
+    SetSymbolValue(CONTROL_STACK_END,(lispobj)th->control_stack_end,th);
+#if defined(LISP_FEATURE_X86) || defined (LISP_FEATURE_X86_64)
+    SetSymbolValue(BINDING_STACK_POINTER,(lispobj)th->binding_stack_pointer,th);
+    SetSymbolValue(ALIEN_STACK,(lispobj)th->alien_stack_pointer,th);
+    SetSymbolValue(PSEUDO_ATOMIC_BITS,(lispobj)th->pseudo_atomic_bits,th);
 #else
     current_binding_stack_pointer=th->binding_stack_pointer;
     current_control_stack_pointer=th->control_stack_start;
 #endif
-#endif    
+#endif
     bind_variable(CURRENT_CATCH_BLOCK,make_fixnum(0),th);
-    bind_variable(CURRENT_UNWIND_PROTECT_BLOCK,make_fixnum(0),th); 
+    bind_variable(CURRENT_UNWIND_PROTECT_BLOCK,make_fixnum(0),th);
     bind_variable(FREE_INTERRUPT_CONTEXT_INDEX,make_fixnum(0),th);
     bind_variable(INTERRUPT_PENDING, NIL,th);
     bind_variable(INTERRUPTS_ENABLED,T,th);
-
-    th->interrupt_data=os_validate(0,(sizeof (struct interrupt_data)));
-    if(all_threads) 
-       memcpy(th->interrupt_data,
-              arch_os_get_current_thread()->interrupt_data,
-              sizeof (struct interrupt_data));
-    else 
-       memcpy(th->interrupt_data,global_interrupt_data,
-              sizeof (struct interrupt_data));
-
-    th->unbound_marker=initial_function;
+    bind_variable(GC_PENDING,NIL,th);
 #ifdef LISP_FEATURE_SB_THREAD
-#if defined(LISP_FEATURE_X86) && defined (LISP_FEATURE_LINUX)
-    kid_pid=
-       clone(new_thread_trampoline,
-             (((void*)th->control_stack_start)+THREAD_CONTROL_STACK_SIZE-4),
-             CLONE_FILES|SIG_THREAD_EXIT|CLONE_VM,th);
-    if(kid_pid<=0) 
-       goto cleanup;
-#else
-#error this stuff presently only works on x86 Linux
-#endif
-#else
-    kid_pid=getpid();
-#endif
-    get_spinlock(&all_threads_lock,kid_pid);
-    th->next=all_threads;
-    all_threads=th;
-    /* note that th->pid is 0 at this time.  We rely on all_threads_lock
-     * to ensure that we don't have >1 thread with pid=0 on the list at once
-     */
-    protect_control_stack_guard_page(th->pid,1);
-    release_spinlock(&all_threads_lock);
-    th->pid=kid_pid;           /* child will not start until this is set */
-#ifndef LISP_FEATURE_SB_THREAD
-    new_thread_trampoline(all_threads);        /*  call_into_lisp */
-    lose("Clever child?  Idiot savant, verging on the.");
+    bind_variable(STOP_FOR_GC_PENDING,NIL,th);
 #endif
 
-    return th->pid;
- cleanup:
-    /* if(th && th->tls_cookie>=0) os_free_tls_pointer(th); */
-    if(spaces) os_invalidate(spaces,
-                            THREAD_CONTROL_STACK_SIZE+BINDING_STACK_SIZE+
-                            ALIEN_STACK_SIZE+dynamic_values_bytes);
-    return 0;
+    th->interrupt_data = (struct interrupt_data *)
+        os_validate(0,(sizeof (struct interrupt_data)));
+    if (!th->interrupt_data) {
+        free_thread_struct(th);
+        return 0;
+    }
+    th->interrupt_data->pending_handler = 0;
+    th->no_tls_value_marker=initial_function;
+
+    th->stepping = NIL;
+    return th;
 }
 
-void destroy_thread (struct thread *th)
-{
-    /* precondition: the unix task has already been killed and exited.
-     * This is called by the parent */
-#ifdef LISP_FEATURE_GENCGC
-    gc_alloc_update_page_tables(0, &th->alloc_region);
+#ifdef LISP_FEATURE_MACH_EXCEPTION_HANDLER
+mach_port_t setup_mach_exception_handling_thread();
+kern_return_t mach_thread_init(mach_port_t thread_exception_port);
+
 #endif
-    get_spinlock(&all_threads_lock,th->pid);
-    if(countdown_to_gc>0) countdown_to_gc--;
-    th->state=STATE_STOPPED;
-    if(th==all_threads) 
-       all_threads=th->next;
-    else {
-       struct thread *th1=all_threads;
-       while(th1->next!=th) th1=th1->next;
-       th1->next=th->next;     /* unlink */
-    }
-    release_spinlock(&all_threads_lock);
-    if(th && th->tls_cookie>=0) arch_os_thread_cleanup(th); 
-    os_invalidate((os_vm_address_t) th->control_stack_start,
-                 ((sizeof (lispobj))
-                  * (th->control_stack_end-th->control_stack_start)) +
-                 BINDING_STACK_SIZE+ALIEN_STACK_SIZE+dynamic_values_bytes+
-                 32*SIGSTKSZ);
-}
 
+void create_initial_thread(lispobj initial_function) {
+    struct thread *th=create_thread_struct(initial_function);
+    if(th) {
+#ifdef LISP_FEATURE_MACH_EXCEPTION_HANDLER
+        kern_return_t ret;
 
-struct thread *find_thread_by_pid(pid_t pid) 
-{
-    struct thread *th;
-    for_each_thread(th)
-       if(th->pid==pid) return th;
-    return 0;
+        setup_mach_exception_handling_thread();
+#endif
+        initial_thread_trampoline(th); /* no return */
+    } else lose("can't create initial thread\n");
 }
 
-/* These are not needed unless #+SB-THREAD, and since sigwaitinfo()
- * doesn't seem to be easily available everywhere (OpenBSD...) it's
- * more trouble than it's worth to compile it when not needed. */
-#if defined LISP_FEATURE_SB_THREAD
-void block_sigcont(void)
+#ifdef LISP_FEATURE_SB_THREAD
+
+#ifndef __USE_XOPEN2K
+extern int pthread_attr_setstack (pthread_attr_t *__attr, void *__stackaddr,
+                                  size_t __stacksize);
+#endif
+
+boolean create_os_thread(struct thread *th,os_thread_t *kid_tid)
 {
-    /* don't allow ourselves to receive SIGCONT while we're in the
-     * "ambiguous" state of being on the queue but not actually stopped.
-     */
-    sigset_t newset;
+    /* The new thread inherits the restrictive signal mask set here,
+     * and enables signals again when it is set up properly. */
+    pthread_attr_t attr;
+    sigset_t newset,oldset;
+    boolean r=1;
+    int retcode, initcode, sizecode, addrcode;
+
+    FSHOW_SIGNAL((stderr,"/create_os_thread: creating new thread\n"));
+
+#ifdef LOCK_CREATE_THREAD
+    retcode = pthread_mutex_lock(&create_thread_lock);
+    gc_assert(retcode == 0);
+    FSHOW_SIGNAL((stderr,"/create_os_thread: got lock\n"));
+#endif
     sigemptyset(&newset);
-    sigaddset(&newset,SIG_DEQUEUE);
-    sigprocmask(SIG_BLOCK, &newset, 0); 
-}
+    /* Blocking deferrable signals is enough, no need to block
+     * SIG_STOP_FOR_GC because the child process is not linked onto
+     * all_threads until it's ready. */
+    sigaddset_deferrable(&newset);
+    thread_sigmask(SIG_BLOCK, &newset, &oldset);
 
-void unblock_sigcont_and_sleep(void)
-{
-    sigset_t set;
-    sigemptyset(&set);
-    sigaddset(&set,SIG_DEQUEUE);
-    do {
-       errno=0;
-       sigwaitinfo(&set,0);
-    }while(errno==EINTR);
-    sigprocmask(SIG_UNBLOCK,&set,0);
+#if defined(LISP_FEATURE_DARWIN)
+#define CONTROL_STACK_ADJUST 8192 /* darwin wants page-aligned stacks */
+#else
+#define CONTROL_STACK_ADJUST 16
+#endif
+
+    if((initcode = pthread_attr_init(&attr)) ||
+       /* FIXME: why do we even have this in the first place? */
+       (pthread_attr_setstack(&attr,th->control_stack_start,
+                              THREAD_CONTROL_STACK_SIZE-CONTROL_STACK_ADJUST)) ||
+#undef CONTROL_STACK_ADJUST
+       (retcode = pthread_create
+        (kid_tid,&attr,(void *(*)(void *))new_thread_trampoline,th))) {
+        FSHOW_SIGNAL((stderr, "init, size, addr = %d, %d, %d\n", initcode, sizecode, addrcode));
+        FSHOW_SIGNAL((stderr, printf("pthread_create returned %d, errno %d\n", retcode, errno)));
+        FSHOW_SIGNAL((stderr, "wanted stack size %d, min stack size %d\n",
+                      THREAD_CONTROL_STACK_SIZE-16, PTHREAD_STACK_MIN));
+        if(retcode < 0) {
+            perror("create_os_thread");
+        }
+        r=0;
+    }
+
+#ifdef QUEUE_FREEABLE_THREAD_STACKS
+    free_freeable_stacks();
+#endif
+    thread_sigmask(SIG_SETMASK,&oldset,0);
+#ifdef LOCK_CREATE_THREAD
+    retcode = pthread_mutex_unlock(&create_thread_lock);
+    gc_assert(retcode == 0);
+    FSHOW_SIGNAL((stderr,"/create_os_thread: released lock\n"));
+#endif
+    return r;
 }
 
-int interrupt_thread(pid_t pid, lispobj function)
-{
-    union sigval sigval;
-    sigval.sival_int=function;
+os_thread_t create_thread(lispobj initial_function) {
+    struct thread *th;
+    os_thread_t kid_tid;
 
-    return sigqueue(pid, SIG_INTERRUPT_THREAD, sigval);
+    /* Assuming that a fresh thread struct has no lisp objects in it,
+     * linking it to all_threads can be left to the thread itself
+     * without fear of gc lossage. initial_function violates this
+     * assumption and must stay pinned until the child starts up. */
+    th = create_thread_struct(initial_function);
+    if(th==0) return 0;
+
+    if (create_os_thread(th,&kid_tid)) {
+        return kid_tid;
+    } else {
+        free_thread_struct(th);
+        return 0;
+    }
 }
 
-int signal_thread_to_dequeue (pid_t pid)
+/* Send the signo to os_thread, retry if the rt signal queue is
+ * full. */
+int
+kill_thread_safely(os_thread_t os_thread, int signo)
 {
-    return kill (pid, SIG_DEQUEUE);
+    int r;
+    /* The man page does not mention EAGAIN as a valid return value
+     * for either pthread_kill or kill. But that's theory, this is
+     * practice. By waiting here we assume that the delivery of this
+     * signal is not necessary for the delivery of the signals in the
+     * queue. In other words, we _assume_ there are no deadlocks. */
+    while ((r=pthread_kill(os_thread,signo))==EAGAIN) {
+        /* wait a bit then try again in the hope of the rt signal
+         * queue not being full */
+        FSHOW_SIGNAL((stderr,"/rt signal queue full\n"));
+        /* FIXME: some kind of backoff (random, exponential) would be
+         * nice. */
+        sleep(1);
+    }
+    return r;
 }
 
+int signal_interrupt_thread(os_thread_t os_thread)
+{
+    int status = kill_thread_safely(os_thread, SIG_INTERRUPT_THREAD);
+    if (status == 0) {
+        return 0;
+    } else if (status == ESRCH) {
+        return -1;
+    } else {
+        lose("cannot send SIG_INTERRUPT_THREAD to thread=%lu: %d, %s\n",
+             os_thread, status, strerror(status));
+    }
+}
 
-/* stopping the world is a two-stage process.  From this thread we signal 
- * all the others with SIG_STOP_FOR_GC.  The handler for this thread does
- * the usual pseudo-atomic checks (we don't want to stop a thread while 
- * it's in the middle of allocation) then kills _itself_ with SIGSTOP.
- * At any given time, countdown_to_gc should reflect the number of threads
- * signalled but which haven't yet come to rest
+/* stopping the world is a two-stage process.  From this thread we signal
+ * all the others with SIG_STOP_FOR_GC.  The handler for this signal does
+ * the usual pseudo-atomic checks (we don't want to stop a thread while
+ * it's in the middle of allocation) then waits for another SIG_STOP_FOR_GC.
  */
 
+/* To avoid deadlocks when gc stops the world all clients of each
+ * mutex must enable or disable SIG_STOP_FOR_GC for the duration of
+ * holding the lock, but they must agree on which. */
 void gc_stop_the_world()
 {
-    /* stop all other threads by sending them SIG_STOP_FOR_GC */
     struct thread *p,*th=arch_os_get_current_thread();
-    pid_t old_pid;
-    int finished=0;
-    do {
-       get_spinlock(&all_threads_lock,th->pid);
-       for(p=all_threads,old_pid=p->pid; p; p=p->next) {
-           if(p==th) continue;
-           if(p->state!=STATE_RUNNING) continue;
-           countdown_to_gc++;
-           p->state=STATE_STOPPING;
-           /* Note no return value check from kill().  If the
-            * thread had been reaped already, we kill it and
-            * increment countdown_to_gc anyway.  This is to avoid
-            * complicating the logic in destroy_thread, which would 
-            * otherwise have to know whether the thread died before or
-            * after it was killed
-            */
-           kill(p->pid,SIG_STOP_FOR_GC);
-       }
-       release_spinlock(&all_threads_lock);
-       sched_yield();
-       /* if everything has stopped, and there is no possibility that
-        * a new thread has been created, we're done.  Otherwise go
-        * round again and signal anything that sprang up since last
-        * time  */
-       if(old_pid==all_threads->pid) {
-           finished=1;
-           for_each_thread(p) 
-               finished = finished &&
-               ((p==th) || (p->state==STATE_STOPPED));
-       }
-    } while(!finished);
+    int status, lock_ret;
+#ifdef LOCK_CREATE_THREAD
+    /* KLUDGE: Stopping the thread during pthread_create() causes deadlock
+     * on FreeBSD. */
+    FSHOW_SIGNAL((stderr,"/gc_stop_the_world:waiting on create_thread_lock, thread=%lu\n",
+                  th->os_thread));
+    lock_ret = pthread_mutex_lock(&create_thread_lock);
+    gc_assert(lock_ret == 0);
+    FSHOW_SIGNAL((stderr,"/gc_stop_the_world:got create_thread_lock, thread=%lu\n",
+                  th->os_thread));
+#endif
+    FSHOW_SIGNAL((stderr,"/gc_stop_the_world:waiting on lock, thread=%lu\n",
+                  th->os_thread));
+    /* keep threads from starting while the world is stopped. */
+    lock_ret = pthread_mutex_lock(&all_threads_lock);      \
+    gc_assert(lock_ret == 0);
+
+    FSHOW_SIGNAL((stderr,"/gc_stop_the_world:got lock, thread=%lu\n",
+                  th->os_thread));
+    /* stop all other threads by sending them SIG_STOP_FOR_GC */
+    for(p=all_threads; p; p=p->next) {
+        gc_assert(p->os_thread != 0);
+        FSHOW_SIGNAL((stderr,"/gc_stop_the_world: p->state: %x\n", p->state));
+        if((p!=th) && ((p->state==STATE_RUNNING))) {
+            FSHOW_SIGNAL((stderr,"/gc_stop_the_world: suspending %x, os_thread %x\n",
+                          p, p->os_thread));
+            status=kill_thread_safely(p->os_thread,SIG_STOP_FOR_GC);
+            if (status==ESRCH) {
+                /* This thread has exited. */
+                gc_assert(p->state==STATE_DEAD);
+            } else if (status) {
+                lose("cannot send suspend thread=%lu: %d, %s\n",
+                     p->os_thread,status,strerror(status));
+            }
+        }
+    }
+    FSHOW_SIGNAL((stderr,"/gc_stop_the_world:signals sent\n"));
+    /* wait for the running threads to stop or finish */
+    for(p=all_threads;p;) {
+        FSHOW_SIGNAL((stderr,"/gc_stop_the_world: th: %p, p: %p\n", th, p));
+        if((p!=th) && (p->state==STATE_RUNNING)) {
+            sched_yield();
+        } else {
+            p=p->next;
+        }
+    }
+    FSHOW_SIGNAL((stderr,"/gc_stop_the_world:end\n"));
 }
 
 void gc_start_the_world()
 {
     struct thread *p,*th=arch_os_get_current_thread();
-    get_spinlock(&all_threads_lock,th->pid);
+    int status, lock_ret;
+    /* if a resumed thread creates a new thread before we're done with
+     * this loop, the new thread will get consed on the front of
+     * all_threads, but it won't have been stopped so won't need
+     * restarting */
+    FSHOW_SIGNAL((stderr,"/gc_start_the_world:begin\n"));
     for(p=all_threads;p;p=p->next) {
-       if(p==th) continue;
-       p->state=STATE_RUNNING;
-       kill(p->pid,SIGCONT);
+        gc_assert(p->os_thread!=0);
+        if((p!=th) && (p->state!=STATE_DEAD)) {
+            if(p->state!=STATE_SUSPENDED) {
+                lose("gc_start_the_world: wrong thread state is %d\n",
+                     fixnum_value(p->state));
+            }
+            FSHOW_SIGNAL((stderr, "/gc_start_the_world: resuming %lu\n",
+                          p->os_thread));
+            p->state=STATE_RUNNING;
+
+#if defined(SIG_RESUME_FROM_GC)
+            status=kill_thread_safely(p->os_thread,SIG_RESUME_FROM_GC);
+#else
+            status=kill_thread_safely(p->os_thread,SIG_STOP_FOR_GC);
+#endif
+            if (status) {
+                lose("cannot resume thread=%lu: %d, %s\n",
+                     p->os_thread,status,strerror(status));
+            }
+        }
     }
-    release_spinlock(&all_threads_lock);
+    /* If we waited here until all threads leave STATE_SUSPENDED, then
+     * SIG_STOP_FOR_GC wouldn't need to be a rt signal. That has some
+     * performance implications, but does away with the 'rt signal
+     * queue full' problem. */
+
+    lock_ret = pthread_mutex_unlock(&all_threads_lock);
+    gc_assert(lock_ret == 0);
+#ifdef LOCK_CREATE_THREAD
+    lock_ret = pthread_mutex_unlock(&create_thread_lock);
+    gc_assert(lock_ret == 0);
+#endif
+
+    FSHOW_SIGNAL((stderr,"/gc_start_the_world:end\n"));
 }
 #endif