(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)))
+ #!+sb-thread
+ (sap-int (sb!vm::current-thread-offset-sap sb!vm::thread-os-thread-slot))
+ #!-sb-thread
+ 0)
(defun init-initial-thread ()
(/show0 "Entering INIT-INITIAL-THREAD")
;;;; Aliens, low level stuff
+(define-alien-routine "kill_safely"
+ integer
+ (os-thread #!-alpha unsigned-long #!+alpha unsigned-int)
+ (signal int))
+
#!+sb-thread
(progn
;; FIXME it would be good to define what a thread id is or isn't
(define-alien-routine ("create_thread" %create-thread)
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)
(thread-yield)
(return-from get-spinlock t))))
(if (and (not *interrupts-enabled*) *allow-with-interrupts*)
- ;; If interrupts are enabled, 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))
+ ;; If interrupts are disabled, but we are allowed to
+ ;; enabled them, check for pending interrupts every once
+ ;; in a while. %CHECK-INTERRUPTS is taking shortcuts, make
+ ;; sure that deferrables are unblocked by doing an empty
+ ;; WITH-INTERRUPTS once.
+ (progn
+ (with-interrupts)
+ (loop
+ (loop repeat 128 do (cas)) ; 128 is arbitrary here
+ (sb!unix::%check-interrupts)))
(loop (cas)))))
t))
(defun release-spinlock (spinlock)
(declare (optimize (speed 3) (safety 0)))
- ;; Simply setting SPINLOCK-VALUE to NIL is not enough as it does not
- ;; propagate to other processors, plus without a memory barrier the
- ;; CPU might reorder instructions allowing code from the critical
- ;; section to leak out. Use COMPARE-AND-SWAP for the memory barrier
- ;; effect and do some sanity checking while we are at it.
- (unless (eq *current-thread*
- (sb!ext:compare-and-swap (spinlock-value spinlock)
- *current-thread* nil))
- (error "Only the owner can release the spinlock ~S." spinlock)))
+ ;; 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
(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
"Acquire MUTEX for NEW-OWNER, which must be a thread or NIL. If
(when (eq new-owner old)
(error "Recursive lock attempt ~S." mutex))
#!-sb-thread
- (if old
- (error "Strange deadlock on ~S in an unithreaded build?" mutex)
- (setf (mutex-%owner mutex) new-owner)))
+ (when old
+ (error "Strange deadlock on ~S in an unithreaded build?" mutex)))
+ #!-sb-thread
+ (setf (mutex-%owner mutex) new-owner)
#!+sb-thread
(progn
;; FIXME: Lutexes do not currently support deadlines, as at least
(setf (mutex-%owner mutex) new-owner)
t)
#!-sb-lutex
+ ;; This is a direct translation 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+)))
+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))))
+ (loop
+ (multiple-value-bind (to-sec to-usec) (decode-timeout nil)
+ (case (with-pinned-objects (mutex)
+ (futex-wait (mutex-state-address mutex)
+ (get-lisp-obj-address +lock-contested+)
+ (or to-sec -1)
+ (or to-usec 0)))
+ ((1) (signal-deadline))
+ ((2))
+ (otherwise (return))))))
(setf old (sb!ext:compare-and-swap (mutex-state mutex)
+lock-free+
+lock-contested+))
RELEASE-MUTEX is not interrupt safe: interrupts should be disabled
around calls to it.
-Signals a WARNING is current thread is not the current owner of the
+Signals a WARNING if current thread is not the current owner of the
mutex."
(declare (type mutex mutex))
;; Order matters: set owner to NIL before releasing state.
(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+)
;; mutex on our way out.
(without-interrupts
(unwind-protect
- (let ((me *current-thread*))
+ (let ((me nil))
;; This setf becomes visible to other CPUS due to the
;; usual memory barrier semantics of lock
;; acquire/release.
;; 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))))
+ (loop
+ (multiple-value-bind (to-sec to-usec) (decode-timeout nil)
+ (case (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))))
+ ((1) (signal-deadline))
+ ((2))
+ ;; EWOULDBLOCK, -1 here, is the possible spurious
+ ;; wakeup case. 0 is the normal wakeup.
+ (otherwise (return))))))
;; 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
(defun condition-notify (queue &optional (n 1))
#!+sb-doc
"Notify N threads waiting on QUEUE. The same mutex that is used in
-the correspoinding condition-wait must be held by this thread during
+the corresponding 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
(defun handle-thread-exit (thread)
(/show0 "HANDLING THREAD EXIT")
- ;; We're going down, can't handle interrupts sanely anymore. GC
- ;; remains enabled.
- (block-deferrable-signals)
;; Lisp-side cleanup
(with-all-threads-lock
(setf (thread-%alive-p thread) nil)
;; 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))
(format nil
"~~@<Terminate this thread (~A)~~@:>"
*current-thread*))
- (unwind-protect
- (progn
- ;; 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)
- (setf (thread-result thread)
- (cons t
- (multiple-value-list
- (funcall real-function)))))
- (handle-thread-exit 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.
- (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))))
+ ;; 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))
"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-mutex ((thread-result-lock thread))
+ (with-system-mutex ((thread-result-lock thread) :allow-with-interrupts t)
(cond ((car (thread-result thread))
- (values-list (cdr (thread-result thread))))
+ (return-from join-thread
+ (values-list (cdr (thread-result thread)))))
(defaultp
- default)
- (t
- (error 'join-thread-error :thread thread)))))
+ (return-from join-thread default))))
+ (error 'join-thread-error :thread thread))
(defun destroy-thread (thread)
#!+sb-doc
`(with-system-mutex ((thread-interruptions-lock ,thread))
,@body))
-;;; Called from the signal handler in C.
+;;; Called from the signal handler.
+#!-win32
(defun run-interruption ()
- (in-interruption ()
- (loop
- (let ((interruption (with-interruptions-lock (*current-thread*)
- (pop (thread-interruptions *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.
+ (let ((interruption (with-interruptions-lock (*current-thread*)
+ (pop (thread-interruptions *current-thread*)))))
+ ;; If there is more to do, then resignal and let the normal
+ ;; interrupt deferral mechanism take care of the rest. From the
+ ;; OS's point of view the signal we are in the handler for is no
+ ;; longer pending, so the signal will not be lost.
+ (when (thread-interruptions *current-thread*)
+ (kill-safely (thread-os-thread *current-thread*) sb!unix:sigpipe))
+ (when interruption
+ (funcall interruption))))
+
(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
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))
- #!-sb-thread
+won't like the effect. FUNCTION runs with interrupts disabled, but
+WITH-INTERRUPTS is allowed in it. Keep in mind that many things may
+enable interrupts (GET-MUTEX when contended, for instance) so the
+first thing to do is usually a WITH-INTERRUPTS or a
+WITHOUT-INTERRUPTS. Within a thread interrupts are queued, they are
+run in same the order they were sent."
+ #!+win32
+ (declare (ignore thread))
+ #!+win32
(with-interrupt-bindings
(with-interrupts (funcall function)))
- #!+sb-thread
- (if (eq thread *current-thread*)
- (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)))))))
+ #!-win32
+ (let ((os-thread (thread-os-thread thread)))
+ (cond ((not os-thread)
+ (error 'interrupt-thread-error :thread thread))
+ (t
+ (with-interruptions-lock (thread)
+ ;; Append to the end of the interruptions queue. It's
+ ;; O(N), but it does not hurt to slow interruptors down a
+ ;; bit when the queue gets long.
+ (setf (thread-interruptions thread)
+ (append (thread-interruptions thread)
+ (list (lambda ()
+ (without-interrupts
+ (allow-with-interrupts
+ (funcall function))))))))
+ (when (minusp (kill-safely os-thread sb!unix:sigpipe))
+ (error 'interrupt-thread-error :thread thread))))))
(defun terminate-thread (thread)
#!+sb-doc