X-Git-Url: http://repo.macrolet.net/gitweb/?a=blobdiff_plain;f=src%2Fcode%2Fsignal.lisp;h=02a215af07f92c5992aed74dad2b8631cc1a4012;hb=60a7d6fe1a3005f89973181c065d2bfa8c974e55;hp=a4c529878aba4eb1ff4de5f6298c0fd67e6e05b0;hpb=5a2b6553fbbbb62fa789350facd0d56bb136045f;p=sbcl.git diff --git a/src/code/signal.lisp b/src/code/signal.lisp index a4c5298..02a215a 100644 --- a/src/code/signal.lisp +++ b/src/code/signal.lisp @@ -36,37 +36,152 @@ ;;; any system calls, and by then the cost of the extra system calls ;;; are lost in the noise when compared with the cost of delivering ;;; the signal in the first place. +;;; +;;; The conditional bindings done by this code here are worth the +;;; trouble as binding is more expensive then read & test -- so +;;; (if *foo* +;;; (foo) +;;; (let ((*foo* t)) +;;; (foo))) +;;; is faster then +;;; (let ((*foo* t)) +;;; (foo)) +;;; provided that the first branch is true "often enough". (defvar *interrupts-enabled* t) (defvar *interrupt-pending* nil) +(defvar *allow-with-interrupts* t) (sb!xc:defmacro without-interrupts (&body body) #!+sb-doc - "Execute BODY in a context impervious to interrupts." - (let ((name (gensym "WITHOUT-INTERRUPTS-BODY-"))) - `(flet ((,name () ,@body)) - (if *interrupts-enabled* - (unwind-protect - (let ((*interrupts-enabled* nil)) - (,name)) - ;; FIXME: Does it matter that an interrupt coming in here - ;; could be executed before any of the pending interrupts? - ;; Or do incoming interrupts have the good grace to check - ;; whether interrupts are pending before executing themselves - ;; immediately? - (when *interrupt-pending* - (receive-pending-interrupt))) - (,name))))) + "Executes BODY with all deferrable interrupts disabled. Deferrable +interrupts arriving during execution of the BODY take effect after BODY has +been executed. + +Deferrable interrupts include most blockable POSIX signals, and +SB-THREAD:INTERRUPT-THREAD. Does not interfere with garbage collection, and +unlike in many traditional Lisps using userspace threads, in SBCL +WITHOUT-INTERRUPTS does not inhibit scheduling of other threads. + +Binds ALLOW-WITH-INTERRUPTS and WITH-LOCAL-INTERRUPTS as a local macros. + +ALLOW-WITH-INTERRUPTS allows the WITH-INTERRUPTS to take effect during the +dynamic scope of its body, unless there is an outer WITHOUT-INTERRUPTS without +a corresponding ALLOW-WITH-INTERRUPTS. + +WITH-LOCAL-INTERRUPTS executes its body with interrupts enabled provided that +for there is an ALLOW-WITH-INTERRUPTS for every WITHOUT-INTERRUPTS surrounding +the current one. WITH-LOCAL-INTERRUPTS is equivalent to: + + (allow-with-interrupts (with-interrupts ...)) + +Care must be taken not to let either ALLOW-WITH-INTERRUPTS or +WITH-LOCAL-INTERRUPTS appear in a function that escapes from inside the +WITHOUT-INTERRUPTS in: + + (without-interrupts + ;; The body of the lambda would be executed with WITH-INTERRUPTS allowed + ;; regardless of the interrupt policy in effect when it is called. + (lambda () (allow-with-interrupts ...))) + + (without-interrupts + ;; The body of the lambda would be executed with interrupts enabled + ;; regardless of the interrupt policy in effect when it is called. + (lambda () (with-local-interrupts ...))) +" + (with-unique-names (outer-allow-with-interrupts) + `(dx-flet ((without-interrupts-thunk (,outer-allow-with-interrupts) + (declare (disable-package-locks allow-with-interrupts + with-interrupts) + (ignorable ,outer-allow-with-interrupts)) + (macrolet ((allow-with-interrupts (&body allow-forms) + `(dx-flet ((allow-with-interrupts-thunk () + ,@allow-forms)) + (call-allowing-with-interrupts + #'allow-with-interrupts-thunk + ,',outer-allow-with-interrupts))) + (with-local-interrupts (&body with-forms) + `(dx-flet ((with-local-interrupts-thunk () + ,@with-forms)) + (call-with-local-interrupts + #'with-local-interrupts-thunk + ,',outer-allow-with-interrupts)))) + (declare (enable-package-locks allow-with-interrupts + with-interrupts)) + ,@body))) + (call-without-interrupts #'without-interrupts-thunk)))) (sb!xc:defmacro with-interrupts (&body body) #!+sb-doc - "Allow interrupts while executing BODY. As interrupts are normally allowed, - this is only useful inside a WITHOUT-INTERRUPTS." - (let ((name (gensym))) - `(flet ((,name () ,@body)) - (if *interrupts-enabled* - (,name) - (let ((*interrupts-enabled* t)) - (when *interrupt-pending* - (receive-pending-interrupt)) - (,name)))))) + "Executes BODY with deferrable interrupts conditionally enabled. If there +are pending interrupts they take effect prior to executing BODY. + +As interrupts are normally allowed WITH-INTERRUPTS only makes sense if there +is an outer WITHOUT-INTERRUPTS with a corresponding ALLOW-WITH-INTERRUPTS: +interrupts are not enabled if any outer WITHOUT-INTERRUPTS is not accompanied +by ALLOW-WITH-INTERRUPTS." + `(dx-flet ((with-interrupts-thunk () ,@body)) + (call-with-interrupts + #'with-interrupts-thunk + (and (not *interrupts-enabled*) *allow-with-interrupts*)))) + +(defun call-allowing-with-interrupts (function allowp) + (declare (function function)) + (if allowp + (let ((*allow-with-interrupts* t)) + (funcall function)) + (funcall function))) + +(defun call-with-interrupts (function allowp) + (declare (function function)) + (if allowp + (let ((*interrupts-enabled* t)) + (when *interrupt-pending* + (receive-pending-interrupt)) + (funcall function)) + (funcall function))) + +;; Distinct from CALL-WITH-INTERRUPTS as it needs to bind both *A-W-I* +;; and *I-E*. +(defun call-with-local-interrupts (function allowp) + (declare (function function)) + (if allowp + (let* ((*allow-with-interrupts* t) + (*interrupts-enabled* t)) + (when *interrupt-pending* + (receive-pending-interrupt)) + (funcall function)) + (funcall function))) + +(defun call-without-interrupts (function) + (declare (function function)) + (flet ((run-without-interrupts () + (if *allow-with-interrupts* + (let ((*allow-with-interrupts* nil)) + (funcall function t)) + (funcall function nil)))) + (if *interrupts-enabled* + (unwind-protect + (let ((*interrupts-enabled* nil)) + (run-without-interrupts)) + ;; If we were interrupted in the protected section, then the + ;; interrupts are still blocked and it remains so until the + ;; pending interrupt is handled. + ;; + ;; If we were not interrupted in the protected section, but + ;; here, then even if the interrupt handler enters another + ;; WITHOUT-INTERRUPTS, the pending interrupt will be handled + ;; immediately upon exit from said WITHOUT-INTERRUPTS, so it + ;; is as if nothing has happened. + (when *interrupt-pending* + (receive-pending-interrupt))) + (run-without-interrupts)))) + +;;; A low-level operation that assumes that *INTERRUPTS-ENABLED* is false, +;;; and *ALLOW-WITH-INTERRUPTS* is true. +(defun %check-interrupts () + ;; Here we check for pending interrupts first, because reading a special + ;; is faster then binding it! + (when *interrupt-pending* + (let ((*interrupts-enabled* t)) + (receive-pending-interrupt))))