;; low-level thread primitives support
;;
- ;; As of SBCL 0.8, this is only supposed to work in x86 Linux, on which
- ;; system it's implemented using clone(2) and the %fs segment register.
- ;; Note that no consistent effort to audit the SBCL library code for
- ;; thread safety has been performed, so caveat executor.
+ ;; As of SBCL 0.8, this is only supposed to work in x86 Linux with
+ ;; NPTL support (usually kernel 2.6, though sme Red Hat distributions
+ ;; with older kernels also have it) and is implemented using clone(2)
+ ;; and the %fs segment register. Note that no consistent effort to
+ ;; audit the SBCL library code for thread safety has been performed,
+ ;; so caveat executor.
; :sb-thread
- ;; Kernel support for futexes (so-called "fast userspace mutexes") is
- ;; available in Linux 2.6 and some versions of 2.4 (Red Hat vendor
- ;; kernels, possibly other vendors too). We can take advantage of
- ;; these to do faster and probably more reliable mutex and condition
- ;; variable support. An SBCL built with this feature will fall back
- ;; to the old system if the futex() syscall is not available at
- ;; runtime
- ; :sb-futex
-
;; Support for detection of unportable code (when applied to the
;; COMMON-LISP package, or SBCL-internal pacakges) or bad-neighbourly
;; code (when applied to user-level packages), relating to material
(sb!alien:define-alien-routine "block_sigcont" void)
(sb!alien:define-alien-routine "unblock_sigcont_and_sleep" void)
-#!+sb-futex
(declaim (inline futex-wait futex-wake))
-#!+sb-futex
(sb!alien:define-alien-routine
"futex_wait" int (word unsigned-long) (old-value unsigned-long))
-#!+sb-futex
(sb!alien:define-alien-routine
"futex_wake" int (word unsigned-long) (n unsigned-long))
-;;; this should only be called while holding the queue spinlock.
-;;; it releases the spinlock before sleeping
-(defun wait-on-queue (queue &optional lock)
- (let ((pid (current-thread-id)))
- (block-sigcont)
- (when lock (release-mutex lock))
- (sb!sys:without-interrupts
- (pushnew pid (waitqueue-data queue)))
- (setf (waitqueue-lock queue) 0)
- (unblock-sigcont-and-sleep)))
-
-;;; this should only be called while holding the queue spinlock. It doesn't
-;;; release it
-(defun dequeue (queue)
- (let ((pid (current-thread-id)))
- (sb!sys:without-interrupts
- (setf (waitqueue-data queue)
- (delete pid (waitqueue-data queue))))))
-
-;;; this should only be called while holding the queue spinlock.
-(defun signal-queue-head (queue)
- (let ((p (car (waitqueue-data queue))))
- (when p (signal-thread-to-dequeue p))))
-
;;;; mutex
-;;; i suspect there may be a race still in this: the futex version requires
-;;; the old mutex value before sleeping, so how do we get away without it
(defun get-mutex (lock &optional new-value (wait-p t))
"Acquire LOCK, setting it to NEW-VALUE or some suitable default value
if NIL. If WAIT-P is non-NIL and the lock is in use, sleep until it
is available"
- (declare (type mutex lock) (optimize (speed 3)))
- (let ((pid (current-thread-id)))
- (unless new-value (setf new-value pid))
- (assert (not (eql new-value (mutex-value lock))))
- (get-spinlock lock 2 pid)
- (loop
- (unless
- ;; args are object slot-num old-value new-value
- (sb!vm::%instance-set-conditional lock 4 nil new-value)
- (dequeue lock)
- (setf (waitqueue-lock lock) 0)
- (return t))
- (unless wait-p
- (setf (waitqueue-lock lock) 0)
- (return nil))
- (wait-on-queue lock nil))))
-
-#!+sb-futex
-(defun get-mutex/futex (lock &optional new-value (wait-p t))
(declare (type mutex lock) (optimize (speed 3)))
(let ((pid (current-thread-id))
old)
(futex-wait (mutex-value-address lock)
(sb!kernel:get-lisp-obj-address old)))))
-(defun release-mutex (lock &optional (new-value nil))
- (declare (type mutex lock))
- ;; we assume the lock is ours to release
- (with-spinlock (lock)
- (setf (mutex-value lock) new-value)
- (signal-queue-head lock)))
-
-#!+sb-futex
-(defun release-mutex/futex (lock)
+(defun release-mutex (lock)
(declare (type mutex lock))
(setf (mutex-value lock) nil)
(futex-wake (mutex-value-address lock) 1))
(assert lock)
(let ((value (mutex-value lock)))
(unwind-protect
- (progn
- (get-spinlock queue 2 (current-thread-id))
- (wait-on-queue queue lock))
- ;; 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.
- (with-spinlock (queue)
- (dequeue queue))
- (get-mutex lock value))))
-
-#!+sb-futex
-(defun condition-wait/futex (queue lock)
- (assert lock)
- (let ((value (mutex-value lock)))
- (unwind-protect
(let ((me (current-thread-id)))
;; XXX we should do something to ensure that the result of this setf
;; is visible to all CPUs
(defun condition-notify (queue)
"Notify one of the processes waiting on QUEUE"
- (with-spinlock (queue) (signal-queue-head queue)))
-
-#!+sb-futex
-(defun condition-notify/futex (queue)
- "Notify one of the processes waiting on QUEUE."
(let ((me (current-thread-id)))
;; no problem if >1 thread notifies during the comment in
;; condition-wait: as long as the value in queue-data isn't the
(setf (waitqueue-data queue) me)
(futex-wake (waitqueue-data-address queue) 1)))
-#!+sb-futex
-(defun condition-broadcast/futex (queue)
+(defun condition-broadcast (queue)
(let ((me (current-thread-id)))
(setf (waitqueue-data queue) me)
(futex-wake (waitqueue-data-address queue) (ash 1 30))))
-(defun condition-broadcast (queue)
- "Notify all of the processes waiting on QUEUE."
- (with-spinlock (queue)
- (map nil #'signal-thread-to-dequeue (waitqueue-data queue))))
-
-;;; Futexes may be available at compile time but not runtime, so we
-;;; default to not using them unless os_init says they're available
-(defun maybe-install-futex-functions ()
- #!+sb-futex
- (unless (zerop (extern-alien "linux_supports_futex" int))
- (sb!ext:without-package-locks
- (setf (fdefinition 'get-mutex) #'get-mutex/futex
- (fdefinition 'release-mutex) #'release-mutex/futex
- (fdefinition 'condition-wait) #'condition-wait/futex
- (fdefinition 'condition-broadcast) #'condition-broadcast/futex
- (fdefinition 'condition-notify) #'condition-notify/futex))
- t))
-
(defun make-thread (function)
(let* ((real-function (coerce function 'function))
(tid
#include "thread.h"
size_t os_vm_page_size;
-#ifdef LISP_FEATURE_SB_FUTEX
+#ifdef LISP_FEATURE_SB_THREAD
#include <linux/unistd.h>
#include <errno.h>
#include "gc.h"
\f
int linux_sparc_siginfo_bug = 0;
-int linux_supports_futex=0;
void os_init(void)
{
major_version);
}
if (!(major_version>2 || minor_version >= 4)) {
-#ifdef LISP_FEATURE_SB_THREAD
- lose("linux kernel 2.4 required for thread-enabled SBCL");
-#endif
#ifdef LISP_FEATURE_SPARC
FSHOW((stderr,"linux kernel %d.%d predates 2.4;\n enabling workarounds for SPARC kernel bugs in signal handling.\n", major_version,minor_version));
linux_sparc_siginfo_bug = 1;
#endif
}
-#ifdef LISP_FEATURE_SB_FUTEX
+#ifdef LISP_FEATURE_SB_THREAD
futex_wait(futex,-1);
- if(errno!=ENOSYS) linux_supports_futex=1;
+ if(errno==ENOSYS) {
+ lose("linux with NPTL support (e.g. kernel 2.6 or newer) required for thread-enabled SBCL");
+ }
#endif
os_vm_page_size = getpagesize();
}
sig_stop_for_gc_handler);
undoably_install_low_level_interrupt_handler(SIG_THREAD_EXIT,
thread_exit_handler);
- if(!linux_supports_futex)
- undoably_install_low_level_interrupt_handler(SIG_DEQUEUE,
- sigcont_handler);
#endif
}
-#ifdef LISP_FEATURE_SB_FUTEX
+#ifdef LISP_FEATURE_SB_THREAD
int futex_wait(int *lock_word, int oldval) {
int t= sys_futex(lock_word,FUTEX_WAIT,oldval, 0);
return t;
projects / sbcl.git / commitdiff