1.0.25.40: fix JOIN-THREAD

[sbcl.git] / src / code / target-thread.lisp

diff --git a/src/code/target-thread.lisp b/src/code/target-thread.lisp
index ba38649..015ebd1 100644 (file)
--- a/src/code/target-thread.lisp
+++ b/src/code/target-thread.lisp
@@ -11,10 +11,15 @@
 
 (in-package "SB!THREAD")
 
 
 (in-package "SB!THREAD")
 

+;;; Of the WITH-PINNED-OBJECTS in this file, not every single one is
+;;; necessary because threads are only supported with the conservative
+;;; gencgc and numbers on the stack (returned by GET-LISP-OBJ-ADDRESS)
+;;; are treated as references.
+

 ;;; set the doc here because in early-thread FDOCUMENTATION is not
 ;;; available, yet
 #!+sb-doc
 ;;; set the doc here because in early-thread FDOCUMENTATION is not
 ;;; available, yet
 #!+sb-doc

-(setf (sb!kernel:fdocumentation '*current-thread* 'variable)
+(setf (fdocumentation '*current-thread* 'variable)

       "Bound in each thread to the thread itself.")
 
 (defstruct (thread (:constructor %make-thread))
       "Bound in each thread to the thread itself.")
 
 (defstruct (thread (:constructor %make-thread))

@@ -22,38 +27,41 @@
   "Thread type. Do not rely on threads being structs as it may change
 in future versions."
   name
   "Thread type. Do not rely on threads being structs as it may change
 in future versions."
   name

-  %sap)
+  %alive-p
+  os-thread
+  interruptions
+  (interruptions-lock (make-mutex :name "thread interruptions lock"))
+  result
+  (result-lock (make-mutex :name "thread result lock")))

 
 #!+sb-doc
 
 #!+sb-doc

-(setf (sb!kernel:fdocumentation 'thread-name 'function)
+(setf (fdocumentation 'thread-name 'function)

       "The name of the thread. Setfable.")
 
 (def!method print-object ((thread thread) stream)
       "The name of the thread. Setfable.")
 
 (def!method print-object ((thread thread) stream)

-  (if (thread-name thread)
-      (print-unreadable-object (thread stream :type t :identity t)
-        (prin1 (thread-name thread) stream))
-      (print-unreadable-object (thread stream :type t :identity t)
-        ;; body is empty => there is only one space between type and
-        ;; identity
-        ))
-  thread)
-
-(defun thread-state (thread)
-  (let ((state
-         (sb!sys:sap-int
-          (sb!sys:sap-ref-sap (thread-%sap thread)
-                              (* sb!vm::thread-state-slot
-                                 sb!vm::n-word-bytes)))))
-    (ecase state
-      (#.(sb!vm:fixnumize 0) :starting)
-      (#.(sb!vm:fixnumize 1) :running)
-      (#.(sb!vm:fixnumize 2) :suspended)
-      (#.(sb!vm:fixnumize 3) :dead))))
+  (print-unreadable-object (thread stream :type t :identity t)
+    (let* ((cookie (list thread))
+           (info (if (thread-alive-p thread)
+                     :running
+                     (multiple-value-list
+                      (join-thread thread :default cookie))))
+           (state (if (eq :running info)
+                      info
+                      (if (eq cookie (car info))
+                          :aborted
+                          :finished)))
+           (values (when (eq :finished state) info)))
+      (format stream
+              "~@[~S ~]~:[~A~;~A~:[ no values~; values: ~:*~{~S~^, ~}~]~]"
+              (thread-name thread)
+              (eq :finished state)
+              state
+              values))))

 
 (defun thread-alive-p (thread)
   #!+sb-doc
   "Check if THREAD is running."
 
 (defun thread-alive-p (thread)
   #!+sb-doc
   "Check if THREAD is running."

-  (not (eq :dead (thread-state thread))))
+  (thread-%alive-p thread))

 
 ;; A thread is eligible for gc iff it has finished and there are no
 ;; more references to it. This list is supposed to keep a reference to
 
 ;; A thread is eligible for gc iff it has finished and there are no
 ;; more references to it. This list is supposed to keep a reference to

@@ -61,171 +69,343 @@ in future versions."
 (defvar *all-threads* ())
 (defvar *all-threads-lock* (make-mutex :name "all threads lock"))
 
 (defvar *all-threads* ())
 (defvar *all-threads-lock* (make-mutex :name "all threads lock"))
 

+(defvar *default-alloc-signal* nil)
+
+(defmacro with-all-threads-lock (&body body)
+  `(with-system-mutex (*all-threads-lock*)
+     ,@body))
+

 (defun list-all-threads ()
   #!+sb-doc
   "Return a list of the live threads."
 (defun list-all-threads ()
   #!+sb-doc
   "Return a list of the live threads."

-  (with-mutex (*all-threads-lock*)
+  (with-all-threads-lock

     (copy-list *all-threads*)))
 
 (declaim (inline current-thread-sap))
 (defun current-thread-sap ()
   (sb!vm::current-thread-offset-sap sb!vm::thread-this-slot))
 
     (copy-list *all-threads*)))
 
 (declaim (inline current-thread-sap))
 (defun current-thread-sap ()
   (sb!vm::current-thread-offset-sap sb!vm::thread-this-slot))
 

-(declaim (inline current-thread-sap-id))
-(defun current-thread-sap-id ()
-  (sb!sys:sap-int
+(declaim (inline current-thread-os-thread))
+(defun current-thread-os-thread ()
+  (sap-int

    (sb!vm::current-thread-offset-sap sb!vm::thread-os-thread-slot)))
 
 (defun init-initial-thread ()
    (sb!vm::current-thread-offset-sap sb!vm::thread-os-thread-slot)))
 
 (defun init-initial-thread ()

+  (/show0 "Entering INIT-INITIAL-THREAD")

   (let ((initial-thread (%make-thread :name "initial thread"
   (let ((initial-thread (%make-thread :name "initial thread"

-                                      :%sap (current-thread-sap))))
+                                      :%alive-p t
+                                      :os-thread (current-thread-os-thread))))

     (setq *current-thread* initial-thread)
     ;; Either *all-threads* is empty or it contains exactly one thread
     ;; in case we are in reinit since saving core with multiple
     ;; threads doesn't work.
     (setq *all-threads* (list initial-thread))))
     (setq *current-thread* initial-thread)
     ;; Either *all-threads* is empty or it contains exactly one thread
     ;; in case we are in reinit since saving core with multiple
     ;; threads doesn't work.
     (setq *all-threads* (list initial-thread))))

+\f

 
 

-;;;;
+;;;; Aliens, low level stuff

 
 #!+sb-thread
 (progn
 
 #!+sb-thread
 (progn

+  ;; FIXME it would be good to define what a thread id is or isn't
+  ;; (our current assumption is that it's a fixnum).  It so happens
+  ;; that on Linux it's a pid, but it might not be on posix thread
+  ;; implementations.

   (define-alien-routine ("create_thread" %create-thread)
   (define-alien-routine ("create_thread" %create-thread)

-      system-area-pointer
-    (lisp-fun-address unsigned-long))
+      unsigned-long (lisp-fun-address unsigned-long))
+
+  (define-alien-routine "signal_interrupt_thread"
+      integer (os-thread unsigned-long))
+
+  (define-alien-routine "block_deferrable_signals"
+      void)
+
+  #!+sb-lutex
+  (progn
+    (declaim (inline %lutex-init %lutex-wait %lutex-wake
+                     %lutex-lock %lutex-unlock))
+
+    (define-alien-routine ("lutex_init" %lutex-init)
+        int (lutex unsigned-long))
+
+    (define-alien-routine ("lutex_wait" %lutex-wait)
+        int (queue-lutex unsigned-long) (mutex-lutex unsigned-long))

 
 

-  (define-alien-routine "block_blockable_signals"
-    void)
+    (define-alien-routine ("lutex_wake" %lutex-wake)
+        int (lutex unsigned-long) (n int))

 
 

-  (define-alien-routine reap-dead-thread void
-    (thread-sap system-area-pointer))
+    (define-alien-routine ("lutex_lock" %lutex-lock)
+        int (lutex unsigned-long))

 
 

-  (declaim (inline futex-wait futex-wake))
+    (define-alien-routine ("lutex_trylock" %lutex-trylock)
+        int (lutex unsigned-long))

 
 

-  (sb!alien:define-alien-routine "futex_wait"
-      int (word unsigned-long) (old-value unsigned-long))
+    (define-alien-routine ("lutex_unlock" %lutex-unlock)
+        int (lutex unsigned-long))

 
 

-  (sb!alien:define-alien-routine "futex_wake"
-      int (word unsigned-long) (n unsigned-long)))
+    (define-alien-routine ("lutex_destroy" %lutex-destroy)
+        int (lutex unsigned-long))
+
+    ;; FIXME: Defining a whole bunch of alien-type machinery just for
+    ;; passing primitive lutex objects directly to foreign functions
+    ;; doesn't seem like fun right now. So instead we just manually
+    ;; pin the lutex, get its address, and let the callee untag it.
+    (defmacro with-lutex-address ((name lutex) &body body)
+      `(let ((,name ,lutex))
+         (with-pinned-objects (,name)
+           (let ((,name (get-lisp-obj-address ,name)))
+             ,@body))))
+
+    (defun make-lutex ()
+      (/show0 "Entering MAKE-LUTEX")
+      ;; Suppress GC until the lutex has been properly registered with
+      ;; the GC.
+      (without-gcing
+        (let ((lutex (sb!vm::%make-lutex)))
+          (/show0 "LUTEX=..")
+          (/hexstr lutex)
+          (with-lutex-address (lutex lutex)
+            (%lutex-init lutex))
+          lutex))))
+
+  #!-sb-lutex
+  (progn
+    (declaim (inline futex-wait %futex-wait futex-wake))
+
+    (define-alien-routine ("futex_wait" %futex-wait)
+        int (word unsigned-long) (old-value unsigned-long)
+        (to-sec long) (to-usec unsigned-long))
+
+    (defun futex-wait (word old to-sec to-usec)
+      (with-interrupts
+        (%futex-wait word old to-sec to-usec)))
+
+    (define-alien-routine "futex_wake"
+        int (word unsigned-long) (n unsigned-long))))

 
 ;;; used by debug-int.lisp to access interrupt contexts
 
 ;;; used by debug-int.lisp to access interrupt contexts

-#!-(and sb-fluid sb-thread) (declaim (inline sb!vm::current-thread-offset-sap))
+#!-(or sb-fluid sb-thread) (declaim (inline sb!vm::current-thread-offset-sap))

 #!-sb-thread
 (defun sb!vm::current-thread-offset-sap (n)
   (declare (type (unsigned-byte 27) n))
 #!-sb-thread
 (defun sb!vm::current-thread-offset-sap (n)
   (declare (type (unsigned-byte 27) n))

-  (sb!sys:sap-ref-sap (alien-sap (extern-alien "all_threads" (* t)))
+  (sap-ref-sap (alien-sap (extern-alien "all_threads" (* t)))

                (* n sb!vm:n-word-bytes)))
 
                (* n sb!vm:n-word-bytes)))
 

-;;;; spinlocks
+#!+sb-thread
+(defun sb!vm::current-thread-offset-sap (n)
+  (declare (type (unsigned-byte 27) n))
+  (sb!vm::current-thread-offset-sap n))
+\f

 
 

-(defstruct spinlock
-  #!+sb-doc
-  "Spinlock type."
-  (name nil :type (or null simple-string))
-  (value 0))
+;;;; Spinlocks

 
 (declaim (inline get-spinlock release-spinlock))
 
 
 (declaim (inline get-spinlock release-spinlock))
 

-;;; The bare 2 here and below are offsets of the slots in the struct.
-;;; There ought to be some better way to get these numbers
-(defun get-spinlock (spinlock new-value)
-  (declare (optimize (speed 3) (safety 0))
-           #!-sb-thread
-           (ignore spinlock new-value))
-  ;; %instance-set-conditional can test for 0 (which is a fixnum) and
-  ;; store any value
-  #!+sb-thread
-  (loop until
-        (eql (sb!vm::%instance-set-conditional spinlock 2 0 new-value) 0)))
+;;; Should always be called with interrupts disabled.
+(defun get-spinlock (spinlock)
+  (declare (optimize (speed 3) (safety 0)))
+  (let* ((new *current-thread*)
+         (old (sb!ext:compare-and-swap (spinlock-value spinlock) nil new)))
+    (when old
+      (when (eq old new)
+        (error "Recursive lock attempt on ~S." spinlock))
+      #!+sb-thread
+      (flet ((cas ()
+               (if (sb!ext:compare-and-swap (spinlock-value spinlock) nil new)
+                   (thread-yield)
+                   (return-from get-spinlock t))))
+        (if (and (not *interrupts-enabled*) *allow-with-interrupts*)
+            ;; If interrupts are disabled, but we are allowed to
+            ;; enabled them, check for pending interrupts every once
+            ;; in a while.
+            (loop
+              (loop repeat 128 do (cas)) ; 128 is arbitrary here
+              (sb!unix::%check-interrupts))
+            (loop (cas)))))
+    t))

 
 (defun release-spinlock (spinlock)
 
 (defun release-spinlock (spinlock)

-  (declare (optimize (speed 3) (safety 0))
-           #!-sb-thread (ignore spinlock))
-  ;; %instance-set-conditional cannot compare arbitrary objects
-  ;; meaningfully, so
-  ;; (sb!vm::%instance-set-conditional spinlock 2 our-value 0)
-  ;; does not work for bignum thread ids.
-  #!+sb-thread
-  (sb!vm::%instance-set spinlock 2 0))
-
-(defmacro with-spinlock ((spinlock) &body body)
-  (sb!int:with-unique-names (lock)
-    `(let ((,lock ,spinlock))
-      (get-spinlock ,lock *current-thread*)
-      (unwind-protect
-           (progn ,@body)
-        (release-spinlock ,lock)))))
-
-;;;; mutexes
-
-(defstruct mutex
-  #!+sb-doc
-  "Mutex type."
-  (name nil :type (or null simple-string))
-  (value nil))
+  (declare (optimize (speed 3) (safety 0)))
+  ;; On x86 and x86-64 we can get away with no memory barriers, (see
+  ;; Linux kernel mailing list "spin_unlock optimization(i386)"
+  ;; thread, summary at
+  ;; http://kt.iserv.nl/kernel-traffic/kt19991220_47.html#1.
+  ;;
+  ;; If the compiler may reorder this with other instructions, insert
+  ;; compiler barrier here.
+  ;;
+  ;; FIXME: this does not work on SMP Pentium Pro and OOSTORE systems,
+  ;; neither on most non-x86 architectures (but we don't have threads
+  ;; on those).
+  (setf (spinlock-value spinlock) nil))
+\f
+
+;;;; Mutexes

 
 #!+sb-doc
 
 #!+sb-doc

-(setf (sb!kernel:fdocumentation 'make-mutex 'function)
+(setf (fdocumentation 'make-mutex 'function)

       "Create a mutex."
       "Create a mutex."

-      (sb!kernel:fdocumentation 'mutex-name 'function)
-      "The name of the mutex. Setfable."
-      (sb!kernel:fdocumentation 'mutex-value 'function)
-      "The value of the mutex. NIL if the mutex is free. Setfable.")
+      (fdocumentation 'mutex-name 'function)
+      "The name of the mutex. Setfable.")

 
 

-#!+sb-thread
-(declaim (inline mutex-value-address))
-#!+sb-thread
-(defun mutex-value-address (mutex)
-  (declare (optimize (speed 3)))
-  (sb!ext:truly-the
-   sb!vm:word
-   (+ (sb!kernel:get-lisp-obj-address mutex)
-      (- (* 3 sb!vm:n-word-bytes) sb!vm:instance-pointer-lowtag))))
-
-(defun get-mutex (mutex &optional new-value (wait-p t))
+#!+(and sb-thread (not sb-lutex))
+(progn
+  (define-structure-slot-addressor mutex-state-address
+      :structure mutex
+      :slot state)
+  ;; Important: current code assumes these are fixnums or other
+  ;; lisp objects that don't need pinning.
+  (defconstant +lock-free+ 0)
+  (defconstant +lock-taken+ 1)
+  (defconstant +lock-contested+ 2))
+
+(defun mutex-owner (mutex)
+  "Current owner of the mutex, NIL if the mutex is free. Naturally,
+this is racy by design (another thread may acquire the mutex after
+this function returns), it is intended for informative purposes. For
+testing whether the current thread is holding a mutex see
+HOLDING-MUTEX-P."
+  ;; Make sure to get the current value.
+  (sb!ext:compare-and-swap (mutex-%owner mutex) nil nil))
+
+(defun get-mutex (mutex &optional (new-owner *current-thread*) (waitp t))

   #!+sb-doc
   #!+sb-doc

-  "Acquire MUTEX, setting it to NEW-VALUE or some suitable default
-value if NIL.  If WAIT-P is non-NIL and the mutex is in use, sleep
-until it is available"
-  (declare (type mutex mutex) (optimize (speed 3)))
-  (unless new-value (setf new-value *current-thread*))
+  "Acquire MUTEX for NEW-OWNER, which must be a thread or NIL. If
+NEW-OWNER is NIL, it defaults to the current thread. If WAITP is
+non-NIL and the mutex is in use, sleep until it is available.
+
+Note: using GET-MUTEX to assign a MUTEX to another thread then the
+current one is not recommended, and liable to be deprecated.
+
+GET-MUTEX is not interrupt safe. The correct way to call it is:
+
+ (WITHOUT-INTERRUPTS
+   ...
+   (ALLOW-WITH-INTERRUPTS (GET-MUTEX ...))
+   ...)
+
+WITHOUT-INTERRUPTS is necessary to avoid an interrupt unwinding the
+call while the mutex is in an inconsistent state while
+ALLOW-WITH-INTERRUPTS allows the call to be interrupted from sleep.
+
+It is recommended that you use WITH-MUTEX instead of calling GET-MUTEX
+directly."
+  (declare (type mutex mutex) (optimize (speed 3))
+           #!-sb-thread (ignore waitp))
+  (unless new-owner
+    (setq new-owner *current-thread*))
+  (let ((old (mutex-%owner mutex)))
+    (when (eq new-owner old)
+      (error "Recursive lock attempt ~S." mutex))
+    #!-sb-thread
+    (when old
+      (error "Strange deadlock on ~S in an unithreaded build?" mutex)))

   #!-sb-thread
   #!-sb-thread

-  (let ((old-value (mutex-value mutex)))
-    (when (and old-value wait-p)
-      (error "In unithread mode, mutex ~S was requested with WAIT-P ~S and ~
-              new-value ~S, but has already been acquired (with value ~S)."
-             mutex wait-p new-value old-value))
-    (setf (mutex-value mutex) new-value)
-    t)
+  (setf (mutex-%owner mutex) new-owner)

   #!+sb-thread
   #!+sb-thread

-  (let (old)
-    (when (eql new-value (mutex-value mutex))
-      (warn "recursive lock attempt ~S~%" mutex)
-      (format *debug-io* "Thread: ~A~%" *current-thread*)
-      (sb!debug:backtrace most-positive-fixnum *debug-io*)
-      (force-output *debug-io*))
-    (loop
-     (unless
-         (setf old (sb!vm::%instance-set-conditional mutex 2 nil new-value))
-       (return t))
-     (unless wait-p (return nil))
-     (futex-wait (mutex-value-address mutex)
-                 (sb!kernel:get-lisp-obj-address old)))))
+  (progn
+    ;; FIXME: Lutexes do not currently support deadlines, as at least
+    ;; on Darwin pthread_foo_timedbar functions are not supported:
+    ;; this means that we probably need to use the Carbon multiprocessing
+    ;; functions on Darwin.
+    ;;
+    ;; FIXME: This is definitely not interrupt safe: what happens if
+    ;; we get hit (1) during the lutex calls (ok, they may be safe,
+    ;; but has that been checked?) (2) after the lutex call, but
+    ;; before setting the mutex owner.
+    #!+sb-lutex
+    (when (zerop (with-lutex-address (lutex (mutex-lutex mutex))
+                   (if waitp
+                       (with-interrupts (%lutex-lock lutex))
+                       (%lutex-trylock lutex))))
+      (setf (mutex-%owner mutex) new-owner)
+      t)
+    #!-sb-lutex
+    ;; This is a direct tranlation of the Mutex 2 algorithm from
+    ;; "Futexes are Tricky" by Ulrich Drepper.
+    (let ((old (sb!ext:compare-and-swap (mutex-state mutex)
+                                        +lock-free+
+                                        +lock-taken+)))
+      (unless (or (eql +lock-free+ old) (not waitp))
+        (tagbody
+         :retry
+           (when (or (eql +lock-contested+ old)
+                     (not (eql +lock-free+
+                               (sb!ext:compare-and-swap (mutex-state mutex)
+                                                        +lock-taken+
+                                                        +lock-contested+))))
+             ;; Wait on the contested lock.
+             (multiple-value-bind (to-sec to-usec) (decode-timeout nil)
+               (when (= 1 (with-pinned-objects (mutex)
+                            (futex-wait (mutex-state-address mutex)
+                                        (get-lisp-obj-address +lock-contested+)
+                                        (or to-sec -1)
+                                        (or to-usec 0))))
+                 (signal-deadline))))
+           (setf old (sb!ext:compare-and-swap (mutex-state mutex)
+                                              +lock-free+
+                                              +lock-contested+))
+           ;; Did we get it?
+           (unless (eql +lock-free+ old)
+             (go :retry))))
+      (cond ((eql +lock-free+ old)
+             (let ((prev (sb!ext:compare-and-swap (mutex-%owner mutex)
+                                                  nil new-owner)))
+               (when prev
+                 (bug "Old owner in free mutex: ~S" prev))
+               t))
+            (waitp
+             (bug "Failed to acquire lock with WAITP."))))))

 
 (defun release-mutex (mutex)
   #!+sb-doc
   "Release MUTEX by setting it to NIL. Wake up threads waiting for
 
 (defun release-mutex (mutex)
   #!+sb-doc
   "Release MUTEX by setting it to NIL. Wake up threads waiting for

-this mutex."
+this mutex.
+
+RELEASE-MUTEX is not interrupt safe: interrupts should be disabled
+around calls to it.
+
+Signals a WARNING if current thread is not the current owner of the
+mutex."

   (declare (type mutex mutex))
   (declare (type mutex mutex))

-  (setf (mutex-value mutex) nil)
+  ;; Order matters: set owner to NIL before releasing state.
+  (let* ((self *current-thread*)
+         (old-owner (sb!ext:compare-and-swap (mutex-%owner mutex) self nil)))
+    (unless  (eql self old-owner)
+      (warn "Releasing ~S, owned by another thread: ~S" mutex old-owner)
+      (setf (mutex-%owner mutex) nil)))

   #!+sb-thread
   #!+sb-thread

-  (futex-wake (mutex-value-address mutex) 1))
-
-;;;; waitqueues/condition variables
+  (progn
+    #!+sb-lutex
+    (with-lutex-address (lutex (mutex-lutex mutex))
+      (%lutex-unlock lutex))
+    #!-sb-lutex
+    ;; FIXME: once ATOMIC-INCF supports struct slots with word sized
+    ;; unsigned-byte type this can be used:
+    ;;
+    ;;     (let ((old (sb!ext:atomic-incf (mutex-state mutex) -1)))
+    ;;       (unless (eql old +lock-free+)
+    ;;         (setf (mutex-state mutex) +lock-free+)
+    ;;         (with-pinned-objects (mutex)
+    ;;           (futex-wake (mutex-state-address mutex) 1))))
+    (let ((old (sb!ext:compare-and-swap (mutex-state mutex)
+                                        +lock-taken+ +lock-free+)))
+      (when (eql old +lock-contested+)
+        (sb!ext:compare-and-swap (mutex-state mutex)
+                                 +lock-contested+ +lock-free+)
+        (with-pinned-objects (mutex)
+          (futex-wake (mutex-state-address mutex) 1))))
+    nil))
+\f
+
+;;;; Waitqueues/condition variables

 
 (defstruct (waitqueue (:constructor %make-waitqueue))
   #!+sb-doc
   "Waitqueue type."
   (name nil :type (or null simple-string))
 
 (defstruct (waitqueue (:constructor %make-waitqueue))
   #!+sb-doc
   "Waitqueue type."
   (name nil :type (or null simple-string))

+  #!+(and sb-lutex sb-thread)
+  (lutex (make-lutex))
+  #!-sb-lutex

   (data nil))
 
 (defun make-waitqueue (&key name)
   (data nil))
 
 (defun make-waitqueue (&key name)

@@ -234,18 +414,13 @@ this mutex."
   (%make-waitqueue :name name))
 
 #!+sb-doc
   (%make-waitqueue :name name))
 
 #!+sb-doc

-(setf (sb!kernel:fdocumentation 'waitqueue-name 'function)
+(setf (fdocumentation 'waitqueue-name 'function)

       "The name of the waitqueue. Setfable.")
 
       "The name of the waitqueue. Setfable.")
 

-#!+sb-thread
-(declaim (inline waitqueue-data-address))
-#!+sb-thread
-(defun waitqueue-data-address (waitqueue)
-  (declare (optimize (speed 3)))
-  (sb!ext:truly-the
-   sb!vm:word
-   (+ (sb!kernel:get-lisp-obj-address waitqueue)
-      (- (* 3 sb!vm:n-word-bytes) sb!vm:instance-pointer-lowtag))))
+#!+(and sb-thread (not sb-lutex))
+(define-structure-slot-addressor waitqueue-data-address
+    :structure waitqueue
+    :slot data)

 
 (defun condition-wait (queue mutex)
   #!+sb-doc
 
 (defun condition-wait (queue mutex)
   #!+sb-doc

@@ -256,52 +431,157 @@ time we reacquire MUTEX and return to the caller."
   (assert mutex)
   #!-sb-thread (error "Not supported in unithread builds.")
   #!+sb-thread
   (assert mutex)
   #!-sb-thread (error "Not supported in unithread builds.")
   #!+sb-thread

-  (let ((value (mutex-value mutex)))
-    (unwind-protect
-         (let ((me *current-thread*))
-           ;; XXX we should do something to ensure that the result of this setf
-           ;; is visible to all CPUs
-           (setf (waitqueue-data queue) me)
-           (release-mutex mutex)
-           ;; Now we go to sleep using futex-wait.  If anyone else
-           ;; manages to grab MUTEX and call CONDITION-NOTIFY during
-           ;; this comment, it will change queue->data, and so
-           ;; futex-wait returns immediately instead of sleeping.
-           ;; Ergo, no lost wakeup
-           (futex-wait (waitqueue-data-address queue)
-                       (sb!kernel:get-lisp-obj-address me)))
-      ;; If we are interrupted while waiting, we should do these things
-      ;; before returning.  Ideally, in the case of an unhandled signal,
-      ;; we should do them before entering the debugger, but this is
-      ;; better than nothing.
-      (get-mutex mutex value))))
-
-(defun condition-notify (queue)
+  (let ((me *current-thread*))
+    (assert (eq me (mutex-%owner mutex)))
+    (/show0 "CONDITION-WAITing")
+    #!+sb-lutex
+    ;; Need to disable interrupts so that we don't miss setting the
+    ;; owner on our way out. (pthread_cond_wait handles the actual
+    ;; re-acquisition.)
+    (without-interrupts
+      (unwind-protect
+           (progn
+             (setf (mutex-%owner mutex) nil)
+             (with-lutex-address (queue-lutex-address (waitqueue-lutex queue))
+               (with-lutex-address (mutex-lutex-address (mutex-lutex mutex))
+                 (with-local-interrupts
+                   (%lutex-wait queue-lutex-address mutex-lutex-address)))))
+        (setf (mutex-%owner mutex) me)))
+    #!-sb-lutex
+    ;; Need to disable interrupts so that we don't miss grabbing the
+    ;; mutex on our way out.
+    (without-interrupts
+      (unwind-protect
+           (let ((me *current-thread*))
+             ;; This setf becomes visible to other CPUS due to the
+             ;; usual memory barrier semantics of lock
+             ;; acquire/release.
+             (setf (waitqueue-data queue) me)
+             (release-mutex mutex)
+             ;; Now we go to sleep using futex-wait. If anyone else
+             ;; manages to grab MUTEX and call CONDITION-NOTIFY during
+             ;; this comment, it will change queue->data, and so
+             ;; futex-wait returns immediately instead of sleeping.
+             ;; Ergo, no lost wakeup. We may get spurious wakeups, but
+             ;; that's ok.
+             (multiple-value-bind (to-sec to-usec) (decode-timeout nil)
+               (when (= 1 (with-pinned-objects (queue me)
+                            (allow-with-interrupts
+                              (futex-wait (waitqueue-data-address queue)
+                                          (get-lisp-obj-address me)
+                                          ;; our way if saying "no
+                                          ;; timeout":
+                                          (or to-sec -1)
+                                          (or to-usec 0)))))
+                 (signal-deadline))))
+        ;; If we are interrupted while waiting, we should do these
+        ;; things before returning. Ideally, in the case of an
+        ;; unhandled signal, we should do them before entering the
+        ;; debugger, but this is better than nothing.
+        (get-mutex mutex)))))
+
+(defun condition-notify (queue &optional (n 1))

   #!+sb-doc
   #!+sb-doc

-  "Notify one of the threads waiting on QUEUE."
-  #!-sb-thread (declare (ignore queue))
+  "Notify N threads waiting on QUEUE. The same mutex that is used in
+the correspoinding condition-wait must be held by this thread during
+this call."
+  #!-sb-thread (declare (ignore queue n))

   #!-sb-thread (error "Not supported in unithread builds.")
   #!+sb-thread
   #!-sb-thread (error "Not supported in unithread builds.")
   #!+sb-thread

-  (let ((me *current-thread*))
+  (declare (type (and fixnum (integer 1)) n))
+  (/show0 "Entering CONDITION-NOTIFY")
+  #!+sb-thread
+  (progn
+    #!+sb-lutex
+    (with-lutex-address (lutex (waitqueue-lutex queue))
+      (%lutex-wake lutex n))

     ;; no problem if >1 thread notifies during the comment in
     ;; condition-wait: as long as the value in queue-data isn't the
     ;; waiting thread's id, it matters not what it is
     ;; XXX we should do something to ensure that the result of this setf
     ;; is visible to all CPUs
     ;; no problem if >1 thread notifies during the comment in
     ;; condition-wait: as long as the value in queue-data isn't the
     ;; waiting thread's id, it matters not what it is
     ;; XXX we should do something to ensure that the result of this setf
     ;; is visible to all CPUs

-    (setf (waitqueue-data queue) me)
-    (futex-wake (waitqueue-data-address queue) 1)))
+    #!-sb-lutex
+    (let ((me *current-thread*))
+      (progn
+        (setf (waitqueue-data queue) me)
+        (with-pinned-objects (queue)
+          (futex-wake (waitqueue-data-address queue) n))))))

 
 (defun condition-broadcast (queue)
   #!+sb-doc
   "Notify all threads waiting on QUEUE."
 
 (defun condition-broadcast (queue)
   #!+sb-doc
   "Notify all threads waiting on QUEUE."

-  #!-sb-thread (declare (ignore queue))
-  #!-sb-thread (error "Not supported in unithread builds.")
-  #!+sb-thread
-  (let ((me *current-thread*))
-    (setf (waitqueue-data queue) me)
-    (futex-wake (waitqueue-data-address queue) (ash 1 30))))
+  (condition-notify queue
+                    ;; On a 64-bit platform truncating M-P-F to an int
+                    ;; results in -1, which wakes up only one thread.
+                    (ldb (byte 29 0)
+                         most-positive-fixnum)))
+\f
+
+;;;; Semaphores
+
+(defstruct (semaphore (:constructor %make-semaphore (name %count)))
+  #!+sb-doc
+  "Semaphore type. The fact that a SEMAPHORE is a STRUCTURE-OBJECT
+should be considered an implementation detail, and may change in the
+future."
+  (name nil :type (or null simple-string))
+  (%count 0 :type (integer 0))
+  (waitcount 0 :type (integer 0))
+  (mutex (make-mutex))
+  (queue (make-waitqueue)))
+
+(setf (fdocumentation 'semaphore-name 'function)
+      "The name of the semaphore INSTANCE. Setfable.")
+
+(declaim (inline semaphore-count))
+(defun semaphore-count (instance)
+  "Returns the current count of the semaphore INSTANCE."
+  (semaphore-%count instance))
+
+(defun make-semaphore (&key name (count 0))
+  #!+sb-doc
+  "Create a semaphore with the supplied COUNT and NAME."
+  (%make-semaphore name count))

 
 

-;;;; job control, independent listeners
+(defun wait-on-semaphore (semaphore)
+  #!+sb-doc
+  "Decrement the count of SEMAPHORE if the count would not be
+negative. Else blocks until the semaphore can be decremented."
+  ;; A more direct implementation based directly on futexes should be
+  ;; possible.
+  ;;
+  ;; We need to disable interrupts so that we don't forget to
+  ;; decrement the waitcount (which would happen if an asynch
+  ;; interrupt should catch us on our way out from the loop.)
+  (with-system-mutex ((semaphore-mutex semaphore) :allow-with-interrupts t)
+    ;; Quick check: is it positive? If not, enter the wait loop.
+    (let ((count (semaphore-%count semaphore)))
+      (if (plusp count)
+          (setf (semaphore-%count semaphore) (1- count))
+          (unwind-protect
+               (progn
+                 (incf (semaphore-waitcount semaphore))
+                 (loop until (plusp (setf count (semaphore-%count semaphore)))
+                       do (condition-wait (semaphore-queue semaphore)
+                                          (semaphore-mutex semaphore)))
+                 (setf (semaphore-%count semaphore) (1- count)))
+            (decf (semaphore-waitcount semaphore)))))))
+
+(defun signal-semaphore (semaphore &optional (n 1))
+  #!+sb-doc
+  "Increment the count of SEMAPHORE by N. If there are threads waiting
+on this semaphore, then N of them is woken up."
+  (declare (type (integer 1) n))
+  ;; Need to disable interrupts so that we don't lose a wakeup after
+  ;; we have incremented the count.
+  (with-system-mutex ((semaphore-mutex semaphore))
+    (let ((waitcount (semaphore-waitcount semaphore))
+          (count (incf (semaphore-%count semaphore) n)))
+      (when (plusp waitcount)
+        (condition-notify (semaphore-queue semaphore) (min waitcount count))))))
+\f
+
+;;;; Job control, independent listeners

 
 (defstruct session
   (lock (make-mutex :name "session lock"))
 
 (defstruct session
   (lock (make-mutex :name "session lock"))

@@ -311,24 +591,30 @@ time we reacquire MUTEX and return to the caller."
 
 (defvar *session* nil)
 
 
 (defvar *session* nil)
 

-;;; the debugger itself tries to acquire the session lock, don't let
+;;; The debugger itself tries to acquire the session lock, don't let

 ;;; funny situations (like getting a sigint while holding the session
 ;;; funny situations (like getting a sigint while holding the session

-;;; lock) occur
+;;; lock) occur. At the same time we need to allow interrupts while
+;;; *waiting* for the session lock for things like GET-FOREGROUND to
+;;; be interruptible.
+;;;
+;;; Take care: we sometimes need to obtain the session lock while
+;;; holding on to *ALL-THREADS-LOCK*, so we must _never_ obtain it
+;;; _after_ getting a session lock! (Deadlock risk.)
+;;;
+;;; FIXME: It would be good to have ordered locks to ensure invariants
+;;; like the above.

 (defmacro with-session-lock ((session) &body body)
 (defmacro with-session-lock ((session) &body body)

-  #!-sb-thread (declare (ignore session))
-  #!-sb-thread
-  `(locally ,@body)
-  #!+sb-thread
-  `(sb!sys:without-interrupts
-    (with-mutex ((session-lock ,session))
-      ,@body)))
+  `(with-system-mutex ((session-lock ,session) :allow-with-interrupts t)
+     ,@body))

 
 (defun new-session ()
   (make-session :threads (list *current-thread*)
                 :interactive-threads (list *current-thread*)))
 
 (defun init-job-control ()
 
 (defun new-session ()
   (make-session :threads (list *current-thread*)
                 :interactive-threads (list *current-thread*)))
 
 (defun init-job-control ()

-  (setf *session* (new-session)))
+  (/show0 "Entering INIT-JOB-CONTROL")
+  (setf *session* (new-session))
+  (/show0 "Exiting INIT-JOB-CONTROL"))

 
 (defun %delete-thread-from-session (thread session)
   (with-session-lock (session)
 
 (defun %delete-thread-from-session (thread session)
   (with-session-lock (session)

@@ -351,10 +637,19 @@ time we reacquire MUTEX and return to the caller."
 ;;; Remove thread from its session, if it has one.
 #!+sb-thread
 (defun handle-thread-exit (thread)
 ;;; Remove thread from its session, if it has one.
 #!+sb-thread
 (defun handle-thread-exit (thread)

-  (with-mutex (*all-threads-lock*)
-    (setq *all-threads* (delete thread *all-threads*)))
-  (when *session*
-    (%delete-thread-from-session thread *session*)))
+  (/show0 "HANDLING THREAD EXIT")
+  ;; Lisp-side cleanup
+  (with-all-threads-lock
+    (setf (thread-%alive-p thread) nil)
+    (setf (thread-os-thread thread) nil)
+    (setq *all-threads* (delete thread *all-threads*))
+    (when *session*
+      (%delete-thread-from-session thread *session*)))
+  #!+sb-lutex
+  (without-gcing
+    (/show0 "FREEING MUTEX LUTEX")
+    (with-lutex-address (lutex (mutex-lutex (thread-interruptions-lock thread)))
+      (%lutex-destroy lutex))))

 
 (defun terminate-session ()
   #!+sb-doc
 
 (defun terminate-session ()
   #!+sb-doc

@@ -393,6 +688,7 @@ interactive."
   #!+sb-thread
   (let ((was-foreground t))
     (loop
   #!+sb-thread
   (let ((was-foreground t))
     (loop

+     (/show0 "Looping in GET-FOREGROUND")

      (with-session-lock (*session*)
        (let ((int-t (session-interactive-threads *session*)))
          (when (eq (car int-t) *current-thread*)
      (with-session-lock (*session*)
        (let ((int-t (session-interactive-threads *session*)))
          (when (eq (car int-t) *current-thread*)

@@ -435,16 +731,16 @@ have the foreground next."
     (labels ((thread-repl ()
                (sb!unix::unix-setsid)
                (let* ((sb!impl::*stdin*
     (labels ((thread-repl ()
                (sb!unix::unix-setsid)
                (let* ((sb!impl::*stdin*

-                       (sb!sys:make-fd-stream in :input t :buffering :line
-                                              :dual-channel-p t))
+                       (make-fd-stream in :input t :buffering :line
+                                       :dual-channel-p t))

                       (sb!impl::*stdout*
                       (sb!impl::*stdout*

-                       (sb!sys:make-fd-stream out :output t :buffering :line
+                       (make-fd-stream out :output t :buffering :line

                                               :dual-channel-p t))
                       (sb!impl::*stderr*
                                               :dual-channel-p t))
                       (sb!impl::*stderr*

-                       (sb!sys:make-fd-stream err :output t :buffering :line
+                       (make-fd-stream err :output t :buffering :line

                                               :dual-channel-p t))
                       (sb!impl::*tty*
                                               :dual-channel-p t))
                       (sb!impl::*tty*

-                       (sb!sys:make-fd-stream err :input t :output t
+                       (make-fd-stream err :input t :output t

                                               :buffering :line
                                               :dual-channel-p t))
                       (sb!impl::*descriptor-handlers* nil))
                                               :buffering :line
                                               :dual-channel-p t))
                       (sb!impl::*descriptor-handlers* nil))

@@ -453,71 +749,142 @@ have the foreground next."
                         (sb!impl::toplevel-repl nil)
                      (sb!int:flush-standard-output-streams))))))
       (make-thread #'thread-repl))))
                         (sb!impl::toplevel-repl nil)
                      (sb!int:flush-standard-output-streams))))))
       (make-thread #'thread-repl))))

+\f

 
 

-;;;; the beef
+;;;; The beef

 
 (defun make-thread (function &key name)
   #!+sb-doc
   "Create a new thread of NAME that runs FUNCTION. When the function
 
 (defun make-thread (function &key name)
   #!+sb-doc
   "Create a new thread of NAME that runs FUNCTION. When the function

-returns the thread exits."
+returns the thread exits. The return values of FUNCTION are kept
+around and can be retrieved by JOIN-THREAD."

   #!-sb-thread (declare (ignore function name))
   #!-sb-thread (error "Not supported in unithread builds.")
   #!+sb-thread
   (let* ((thread (%make-thread :name name))
   #!-sb-thread (declare (ignore function name))
   #!-sb-thread (error "Not supported in unithread builds.")
   #!+sb-thread
   (let* ((thread (%make-thread :name name))

-         (setup-p nil)
+         (setup-sem (make-semaphore :name "Thread setup semaphore"))

          (real-function (coerce function 'function))
          (real-function (coerce function 'function))

-         (thread-sap
-          ;; don't let the child inherit *CURRENT-THREAD* because that
-          ;; can prevent gc'ing this thread while the child runs
-          (let ((*current-thread* nil))
-            (%create-thread
-             (sb!kernel:get-lisp-obj-address
-              (lambda ()
-                ;; FIXME: use semaphores?
-                (loop until setup-p)
-                ;; in time we'll move some of the binding presently done in C
-                ;; here too
-                (let ((*current-thread* thread)
-                      (sb!kernel::*restart-clusters* nil)
-                      (sb!kernel::*handler-clusters* nil)
-                      (sb!kernel::*condition-restarts* nil)
-                      (sb!impl::*descriptor-handlers* nil)) ; serve-event
-                  ;; can't use handling-end-of-the-world, because that flushes
-                  ;; output streams, and we don't necessarily have any (or we
-                  ;; could be sharing them)
-                  (unwind-protect
-                       (catch 'sb!impl::toplevel-catcher
-                         (catch 'sb!impl::%end-of-the-world
-                           (with-simple-restart
-                               (terminate-thread
-                                (format nil
-                                        "~~@<Terminate this thread (~A)~~@:>"
-                                        *current-thread*))
-                             ;; now that most things have a chance to
-                             ;; work properly without messing up other
-                             ;; threads, it's time to enable signals
-                             (sb!unix::reset-signal-mask)
-                             (unwind-protect
-                                  (funcall real-function)
-                               ;; we're going down, can't handle
-                               ;; interrupts sanely anymore
-                               (let ((sb!impl::*gc-inhibit* t))
-                                 (block-blockable-signals)
-                                 ;; and remove what can be the last
-                                 ;; reference to this thread
-                                 (handle-thread-exit thread))))))
-                    0))
-                (values)))))))
-    (when (sb!sys:sap= thread-sap (sb!sys:int-sap 0))
-      (error "Can't create a new thread"))
-    (setf (thread-%sap thread) thread-sap)
-    (with-mutex (*all-threads-lock*)
-      (push thread *all-threads*))
-    (with-session-lock (*session*)
-      (push thread (session-threads *session*)))
-    (setq setup-p t)
-    (sb!impl::finalize thread (lambda () (reap-dead-thread thread-sap)))
-    thread))
+         (initial-function
+          (lambda ()
+            ;; In time we'll move some of the binding presently done in C
+            ;; here too.
+            ;;
+            ;; KLUDGE: Here we have a magic list of variables that are
+            ;; not thread-safe for one reason or another.  As people
+            ;; report problems with the thread safety of certain
+            ;; variables, (e.g. "*print-case* in multiple threads
+            ;; broken", sbcl-devel 2006-07-14), we add a few more
+            ;; bindings here.  The Right Thing is probably some variant
+            ;; of Allegro's *cl-default-special-bindings*, as that is at
+            ;; least accessible to users to secure their own libraries.
+            ;;   --njf, 2006-07-15
+            ;;
+            ;; As it is, this lambda must not cons until we are ready
+            ;; to run GC. Be very careful.
+            (let* ((*current-thread* thread)
+                   (*restart-clusters* nil)
+                   (*handler-clusters* (sb!kernel::initial-handler-clusters))
+                   (*condition-restarts* nil)
+                   (sb!impl::*deadline* nil)
+                   (sb!impl::*step-out* nil)
+                   ;; internal printer variables
+                   (sb!impl::*previous-case* nil)
+                   (sb!impl::*previous-readtable-case* nil)
+                   (empty (vector))
+                   (sb!impl::*merge-sort-temp-vector* empty)
+                   (sb!impl::*zap-array-data-temp* empty)
+                   (sb!impl::*internal-symbol-output-fun* nil)
+                   (sb!impl::*descriptor-handlers* nil)) ; serve-event
+              ;; Binding from C
+              (setf sb!vm:*alloc-signal* *default-alloc-signal*)
+              (setf (thread-os-thread thread) (current-thread-os-thread))
+              (with-mutex ((thread-result-lock thread))
+                (with-all-threads-lock
+                  (push thread *all-threads*))
+                (with-session-lock (*session*)
+                  (push thread (session-threads *session*)))
+                (setf (thread-%alive-p thread) t)
+                (signal-semaphore setup-sem)
+                ;; can't use handling-end-of-the-world, because that flushes
+                ;; output streams, and we don't necessarily have any (or we
+                ;; could be sharing them)
+                (catch 'sb!impl::toplevel-catcher
+                  (catch 'sb!impl::%end-of-the-world
+                    (with-simple-restart
+                        (terminate-thread
+                         (format nil
+                                 "~~@<Terminate this thread (~A)~~@:>"
+                                 *current-thread*))
+                      (without-interrupts
+                        (unwind-protect
+                             (with-local-interrupts
+                               ;; Now that most things have a chance
+                               ;; to work properly without messing up
+                               ;; other threads, it's time to enable
+                               ;; signals.
+                               (sb!unix::unblock-deferrable-signals)
+                               (setf (thread-result thread)
+                                     (cons t
+                                           (multiple-value-list
+                                            (funcall real-function))))
+                               ;; Try to block deferrables. An
+                               ;; interrupt may unwind it, but for a
+                               ;; normal exit it prevents interrupt
+                               ;; loss.
+                               (block-deferrable-signals))
+                          ;; We're going down, can't handle interrupts
+                          ;; sanely anymore. GC remains enabled.
+                          (block-deferrable-signals)
+                          ;; We don't want to run interrupts in a dead
+                          ;; thread when we leave WITHOUT-INTERRUPTS.
+                          ;; This potentially causes important
+                          ;; interupts to be lost: SIGINT comes to
+                          ;; mind.
+                          (setq *interrupt-pending* nil)
+                          (handle-thread-exit thread))))))))
+            (values))))
+    ;; If the starting thread is stopped for gc before it signals the
+    ;; semaphore then we'd be stuck.
+    (assert (not *gc-inhibit*))
+    ;; Keep INITIAL-FUNCTION pinned until the child thread is
+    ;; initialized properly. Wrap the whole thing in
+    ;; WITHOUT-INTERRUPTS because we pass INITIAL-FUNCTION to another
+    ;; thread.
+    (without-interrupts
+      (with-pinned-objects (initial-function)
+        (let ((os-thread
+               (%create-thread
+                (get-lisp-obj-address initial-function))))
+          (when (zerop os-thread)
+            (error "Can't create a new thread"))
+          (wait-on-semaphore setup-sem)
+          thread)))))
+
+(define-condition join-thread-error (error)
+  ((thread :reader join-thread-error-thread :initarg :thread))
+  #!+sb-doc
+  (:documentation "Joining thread failed.")
+  (:report (lambda (c s)
+             (format s "Joining thread failed: thread ~A ~
+                        has not returned normally."
+                     (join-thread-error-thread c)))))
+
+#!+sb-doc
+(setf (fdocumentation 'join-thread-error-thread 'function)
+      "The thread that we failed to join.")
+
+(defun join-thread (thread &key (default nil defaultp))
+  #!+sb-doc
+  "Suspend current thread until THREAD exits. Returns the result
+values of the thread function. If the thread does not exit normally,
+return DEFAULT if given or else signal JOIN-THREAD-ERROR."
+  (with-system-mutex ((thread-result-lock thread) :allow-with-interrupts t)
+    (cond ((car (thread-result thread))
+           (return-from join-thread
+             (values-list (cdr (thread-result thread)))))
+          (defaultp
+           (return-from join-thread default))))
+  (error 'join-thread-error :thread thread))

 
 (defun destroy-thread (thread)
   #!+sb-doc
 
 (defun destroy-thread (thread)
   #!+sb-doc

@@ -525,49 +892,68 @@ returns the thread exits."
   (terminate-thread thread))
 
 (define-condition interrupt-thread-error (error)
   (terminate-thread thread))
 
 (define-condition interrupt-thread-error (error)

-  ((thread :reader interrupt-thread-error-thread :initarg :thread)
-   (errno :reader interrupt-thread-error-errno :initarg :errno))
+  ((thread :reader interrupt-thread-error-thread :initarg :thread))

   #!+sb-doc
   (:documentation "Interrupting thread failed.")
   (:report (lambda (c s)
   #!+sb-doc
   (:documentation "Interrupting thread failed.")
   (:report (lambda (c s)

-             (format s "interrupt thread ~A failed (~A: ~A)"
-                     (interrupt-thread-error-thread c)
-                     (interrupt-thread-error-errno c)
-                     (strerror (interrupt-thread-error-errno c))))))
+             (format s "Interrupt thread failed: thread ~A has exited."
+                     (interrupt-thread-error-thread c)))))

 
 #!+sb-doc
 
 #!+sb-doc

-(setf (sb!kernel:fdocumentation 'interrupt-thread-error-thread 'function)
-      "The thread that was not interrupted."
-      (sb!kernel:fdocumentation 'interrupt-thread-error-errno 'function)
-      "The reason why the interruption failed.")
+(setf (fdocumentation 'interrupt-thread-error-thread 'function)
+      "The thread that was not interrupted.")

 
 

+(defmacro with-interruptions-lock ((thread) &body body)
+  `(with-system-mutex ((thread-interruptions-lock ,thread))
+     ,@body))
+
+;;; Called from the signal handler in C.
+(defun run-interruption ()
+  (in-interruption ()
+    (loop
+     (let ((interruption (with-interruptions-lock (*current-thread*)
+                           (pop (thread-interruptions *current-thread*)))))
+       ;; Resignalling after popping one works fine, because from the
+       ;; OS's point of view we have returned from the signal handler
+       ;; (thanks to arrange_return_to_lisp_function) so at least one
+       ;; more signal will be delivered.
+       (when (thread-interruptions *current-thread*)
+         (signal-interrupt-thread (thread-os-thread *current-thread*)))
+       (if interruption
+           (with-interrupts
+             (funcall interruption))
+           (return))))))
+
+;;; The order of interrupt execution is peculiar. If thread A
+;;; interrupts thread B with I1, I2 and B for some reason receives I1
+;;; when FUN2 is already on the list, then it is FUN2 that gets to run
+;;; first. But when FUN2 is run SIG_INTERRUPT_THREAD is enabled again
+;;; and I2 hits pretty soon in FUN2 and run FUN1. This is of course
+;;; just one scenario, and the order of thread interrupt execution is
+;;; undefined.

 (defun interrupt-thread (thread function)
   #!+sb-doc
   "Interrupt the live THREAD and make it run FUNCTION. A moderate
 (defun interrupt-thread (thread function)
   #!+sb-doc
   "Interrupt the live THREAD and make it run FUNCTION. A moderate

-degree of care is expected for use of interrupt-thread, due to its
+degree of care is expected for use of INTERRUPT-THREAD, due to its

 nature: if you interrupt a thread that was holding important locks
 then do something that turns out to need those locks, you probably
 won't like the effect."
   #!-sb-thread (declare (ignore thread))
 nature: if you interrupt a thread that was holding important locks
 then do something that turns out to need those locks, you probably
 won't like the effect."
   #!-sb-thread (declare (ignore thread))

-  ;; not quite perfect, because it does not take WITHOUT-INTERRUPTS
-  ;; into account

   #!-sb-thread
   #!-sb-thread

-  (funcall function)
+  (with-interrupt-bindings
+    (with-interrupts (funcall function)))

   #!+sb-thread
   (if (eq thread *current-thread*)
   #!+sb-thread
   (if (eq thread *current-thread*)

-      (funcall function)
-      (let ((function (coerce function 'function)))
-        (multiple-value-bind (res err)
-            ;; protect against gcing just when the ub32 address is
-            ;; just ready to be passed to C
-            (sb!sys::with-pinned-objects (function)
-              (sb!unix::syscall ("interrupt_thread"
-                                 system-area-pointer sb!alien:unsigned-long)
-                                thread
-                                (thread-%sap thread)
-                                (sb!kernel:get-lisp-obj-address function)))
-          (unless res
-            (error 'interrupt-thread-error :thread thread :errno err))))))
+      (with-interrupt-bindings
+        (with-interrupts (funcall function)))
+      (let ((os-thread (thread-os-thread thread)))
+        (cond ((not os-thread)
+               (error 'interrupt-thread-error :thread thread))
+              (t
+               (with-interruptions-lock (thread)
+                 (push function (thread-interruptions thread)))
+               (when (minusp (signal-interrupt-thread os-thread))
+                 (error 'interrupt-thread-error :thread thread)))))))

 
 (defun terminate-thread (thread)
   #!+sb-doc
 
 (defun terminate-thread (thread)
   #!+sb-doc

@@ -575,16 +961,82 @@ won't like the effect."
 SB-EXT:QUIT - the usual cleanup forms will be evaluated"
   (interrupt-thread thread 'sb!ext:quit))
 
 SB-EXT:QUIT - the usual cleanup forms will be evaluated"
   (interrupt-thread thread 'sb!ext:quit))
 

-;;; internal use only.  If you think you need to use this, either you
+(define-alien-routine "thread_yield" int)
+
+#!+sb-doc
+(setf (fdocumentation 'thread-yield 'function)
+      "Yield the processor to other threads.")
+
+;;; internal use only.  If you think you need to use these, either you

 ;;; are an SBCL developer, are doing something that you should discuss
 ;;; with an SBCL developer first, or are doing something that you
 ;;; should probably discuss with a professional psychiatrist first
 #!+sb-thread
 ;;; are an SBCL developer, are doing something that you should discuss
 ;;; with an SBCL developer first, or are doing something that you
 ;;; should probably discuss with a professional psychiatrist first
 #!+sb-thread

-(defun symbol-value-in-thread (symbol thread)
-  (let ((thread-sap (thread-%sap thread)))
-    (let* ((index (sb!vm::symbol-tls-index symbol))
-           (tl-val (sb!sys:sap-ref-word thread-sap
-                                        (* sb!vm:n-word-bytes index))))
-      (if (eql tl-val sb!vm::unbound-marker-widetag)
-          (sb!vm::symbol-global-value symbol)
-          (sb!kernel:make-lisp-obj tl-val)))))
+(progn
+  (defun %thread-sap (thread)
+    (let ((thread-sap (alien-sap (extern-alien "all_threads" (* t))))
+          (target (thread-os-thread thread)))
+      (loop
+        (when (sap= thread-sap (int-sap 0)) (return nil))
+        (let ((os-thread (sap-ref-word thread-sap
+                                       (* sb!vm:n-word-bytes
+                                          sb!vm::thread-os-thread-slot))))
+          (when (= os-thread target) (return thread-sap))
+          (setf thread-sap
+                (sap-ref-sap thread-sap (* sb!vm:n-word-bytes
+                                           sb!vm::thread-next-slot)))))))
+
+  (defun %symbol-value-in-thread (symbol thread)
+    (tagbody
+       ;; Prevent the dead from dying completely while we look for the
+       ;; TLS area...
+       (with-all-threads-lock
+         (if (thread-alive-p thread)
+             (let* ((offset (* sb!vm:n-word-bytes
+                               (sb!vm::symbol-tls-index symbol)))
+                    (tl-val (sap-ref-word (%thread-sap thread) offset)))
+               (if (eql tl-val sb!vm::no-tls-value-marker-widetag)
+                   (go :unbound)
+                   (return-from %symbol-value-in-thread
+                     (values (make-lisp-obj tl-val) t))))
+             (return-from %symbol-value-in-thread (values nil nil))))
+     :unbound
+       (error "Cannot read thread-local symbol value: ~S unbound in ~S"
+              symbol thread)))
+
+  (defun %set-symbol-value-in-thread (symbol thread value)
+    (tagbody
+       (with-pinned-objects (value)
+         ;; Prevent the dead from dying completely while we look for
+         ;; the TLS area...
+         (with-all-threads-lock
+           (if (thread-alive-p thread)
+               (let* ((offset (* sb!vm:n-word-bytes
+                                 (sb!vm::symbol-tls-index symbol)))
+                      (sap (%thread-sap thread))
+                      (tl-val (sap-ref-word sap offset)))
+                 (if (eql tl-val sb!vm::no-tls-value-marker-widetag)
+                     (go :unbound)
+                     (setf (sap-ref-word sap offset)
+                           (get-lisp-obj-address value)))
+                 (return-from %set-symbol-value-in-thread (values value t)))
+               (return-from %set-symbol-value-in-thread (values nil nil)))))
+     :unbound
+       (error "Cannot set thread-local symbol value: ~S unbound in ~S"
+              symbol thread))))
+
+(defun sb!vm::locked-symbol-global-value-add (symbol-name delta)
+  (sb!vm::locked-symbol-global-value-add symbol-name delta))
+\f
+
+;;;; Stepping
+
+(defun thread-stepping ()
+  (make-lisp-obj
+   (sap-ref-word (current-thread-sap)
+                 (* sb!vm::thread-stepping-slot sb!vm:n-word-bytes))))
+
+(defun (setf thread-stepping) (value)
+  (setf (sap-ref-word (current-thread-sap)
+                      (* sb!vm::thread-stepping-slot sb!vm:n-word-bytes))
+        (get-lisp-obj-address value)))