src/code/serve-event.lisp

   1 ;;;; This software is part of the SBCL system. See the README file for
   2 ;;;; more information.
   3 ;;;;
   4 ;;;; This software is derived from the CMU CL system, which was
   5 ;;;; written at Carnegie Mellon University and released into the
   6 ;;;; public domain. The software is in the public domain and is
   7 ;;;; provided with absolutely no warranty. See the COPYING and CREDITS
   8 ;;;; files for more information.
   9
  10 (in-package "SB!IMPL")
  11
  12 ;;;; file descriptor I/O noise
  13
  14 (defstruct (handler
  15             (:constructor make-handler (direction descriptor function))
  16             (:copier nil))
  17   ;; Reading or writing...
  18   (direction nil :type (member :input :output))
  19   ;; File descriptor this handler is tied to.
  20   (descriptor 0 :type (mod #.sb!unix:fd-setsize))
  21   ;; T iff this handler is running.
  22   ;;
  23   ;; FIXME: unused. At some point this used to be set to T
  24   ;; around the call to the handler-function, but that was commented
  25   ;; out with the verbose explantion "Doesn't work -- ACK".
  26   active
  27   ;; Function to call.
  28   (function nil :type function)
  29   ;; T if this descriptor is bogus.
  30   bogus)
  31
  32 (def!method print-object ((handler handler) stream)
  33   (print-unreadable-object (handler stream :type t)
  34     (format stream
  35             "~A on ~:[~;BOGUS ~]descriptor ~W: ~S"
  36             (handler-direction handler)
  37             (handler-bogus handler)
  38             (handler-descriptor handler)
  39             (handler-function handler))))
  40
  41 (defvar *descriptor-handlers* nil
  42   #!+sb-doc
  43   "List of all the currently active handlers for file descriptors")
  44
  45 (sb!xc:defmacro with-descriptor-handlers (&body forms)
  46   ;; FD-STREAM functionality can add and remove descriptors on it's
  47   ;; own, so getting an interrupt while modifying this and the
  48   ;; starting to recursively modify it could lose...
  49   `(without-interrupts ,@forms))
  50
  51 (defun list-all-descriptor-handlers ()
  52   (with-descriptor-handlers
  53     (copy-list *descriptor-handlers*)))
  54
  55 (defun select-descriptor-handlers (function)
  56   (declare (function function))
  57   (with-descriptor-handlers
  58     (remove-if-not function *descriptor-handlers*)))
  59
  60 (defun map-descriptor-handlers (function)
  61   (declare (function function))
  62   (with-descriptor-handlers
  63     (dolist (handler *descriptor-handlers*)
  64       (funcall function handler))))
  65
  66 ;;; Add a new handler to *descriptor-handlers*.
  67 (defun add-fd-handler (fd direction function)
  68   #!+sb-doc
  69   "Arange to call FUNCTION whenever FD is usable. DIRECTION should be
  70   either :INPUT or :OUTPUT. The value returned should be passed to
  71   SYSTEM:REMOVE-FD-HANDLER when it is no longer needed."
  72   (unless (member direction '(:input :output))
  73     ;; FIXME: should be TYPE-ERROR?
  74     (error "Invalid direction ~S, must be either :INPUT or :OUTPUT" direction))
  75   (let ((handler (make-handler direction fd function)))
  76     (with-descriptor-handlers
  77       (push handler *descriptor-handlers*))
  78     handler))
  79
  80 ;;; Remove an old handler from *descriptor-handlers*.
  81 (defun remove-fd-handler (handler)
  82   #!+sb-doc
  83   "Removes HANDLER from the list of active handlers."
  84   (with-descriptor-handlers
  85     (setf *descriptor-handlers*
  86           (delete handler *descriptor-handlers*))))
  87
  88 ;;; Search *descriptor-handlers* for any reference to fd, and nuke 'em.
  89 (defun invalidate-descriptor (fd)
  90   #!+sb-doc
  91   "Remove any handers refering to fd. This should only be used when attempting
  92   to recover from a detected inconsistancy."
  93   (with-descriptor-handlers
  94     (setf *descriptor-handlers*
  95           (delete fd *descriptor-handlers*
  96                   :key #'handler-descriptor))))
  97
  98 ;;; Add the handler to *descriptor-handlers* for the duration of BODY.
  99 (defmacro with-fd-handler ((fd direction function) &rest body)
 100   #!+sb-doc
 101   "Establish a handler with SYSTEM:ADD-FD-HANDLER for the duration of BODY.
 102    DIRECTION should be either :INPUT or :OUTPUT, FD is the file descriptor to
 103    use, and FUNCTION is the function to call whenever FD is usable."
 104   (let ((handler (gensym)))
 105     `(let (,handler)
 106        (unwind-protect
 107            (progn
 108              (setf ,handler (add-fd-handler ,fd ,direction ,function))
 109              ,@body)
 110          (when ,handler
 111            (remove-fd-handler ,handler))))))
 112
 113 ;;; First, get a list and mark bad file descriptors. Then signal an error
 114 ;;; offering a few restarts.
 115 (defun handler-descriptors-error ()
 116   (let ((bogus-handlers nil))
 117     (dolist (handler (list-all-descriptor-handlers))
 118       (unless (or (handler-bogus handler)
 119                   (sb!unix:unix-fstat (handler-descriptor handler)))
 120         (setf (handler-bogus handler) t)
 121         (push handler bogus-handlers)))
 122     (restart-case (error "~S ~[have~;has a~:;have~] bad file descriptor~:P."
 123                          bogus-handlers (length bogus-handlers))
 124       (remove-them ()
 125         :report "Remove bogus handlers."
 126         (with-descriptor-handlers
 127           (setf *descriptor-handlers*
 128                 (delete-if #'handler-bogus *descriptor-handlers*))))
 129       (retry-them ()
 130         :report "Retry bogus handlers."
 131        (dolist (handler bogus-handlers)
 132          (setf (handler-bogus handler) nil)))
 133       (continue ()
 134         :report "Go on, leaving handlers marked as bogus.")))
 135   nil)
 136
 137 \f
 138 ;;;; SERVE-ALL-EVENTS, SERVE-EVENT, and friends
 139
 140 ;;; Wait until FD is usable for DIRECTION. The timeout given to serve-event is
 141 ;;; recalculated each time through the loop so that WAIT-UNTIL-FD-USABLE will
 142 ;;; timeout at the correct time irrespective of how many events are handled in
 143 ;;; the meantime.
 144 (defun wait-until-fd-usable (fd direction &optional timeout)
 145   #!+sb-doc
 146   "Wait until FD is usable for DIRECTION. DIRECTION should be either :INPUT or
 147 :OUTPUT. TIMEOUT, if supplied, is the number of seconds to wait before giving
 148 up."
 149   (prog (usable)
 150    :restart
 151      (multiple-value-bind (to-sec to-usec stop-sec stop-usec signalp)
 152          (decode-timeout timeout)
 153        (declare (type (or integer null) to-sec to-usec))
 154        (with-fd-handler (fd direction (lambda (fd)
 155                                         (declare (ignore fd))
 156                                         (setf usable t)))
 157          (loop
 158            (sub-serve-event to-sec to-usec signalp)
 159            (when usable
 160              (return-from wait-until-fd-usable t))
 161            (when to-sec
 162              (multiple-value-bind (sec usec)
 163                  (decode-internal-time (get-internal-real-time))
 164                (setf to-sec (- stop-sec sec))
 165                (cond ((> usec stop-usec)
 166                       (decf to-sec)
 167                       (setf to-usec (- (+ stop-usec 1000000) usec)))
 168                      (t
 169                       (setf to-usec (- stop-usec usec)))))
 170              (when (or (minusp to-sec) (minusp to-usec))
 171                (if signalp
 172                    (progn
 173                      (signal-deadline)
 174                      (go :restart))
 175                    (return-from wait-until-fd-usable nil)))))))))
 176 \f
 177 ;;; Wait for up to timeout seconds for an event to happen. Make sure all
 178 ;;; pending events are processed before returning.
 179 (defun serve-all-events (&optional timeout)
 180   #!+sb-doc
 181   "SERVE-ALL-EVENTS calls SERVE-EVENT with the specified timeout. If
 182 SERVE-EVENT does something (returns T) it loops over SERVE-EVENT with a
 183 timeout of 0 until there are no more events to serve. SERVE-ALL-EVENTS returns
 184 T if SERVE-EVENT did something and NIL if not."
 185   (do ((res nil)
 186        (sval (serve-event timeout) (serve-event 0)))
 187       ((null sval) res)
 188     (setq res t)))
 189
 190 ;;; Serve a single set of events.
 191 (defun serve-event (&optional timeout)
 192   #!+sb-doc
 193   "Receive pending events on all FD-STREAMS and dispatch to the appropriate
 194 handler functions. If timeout is specified, server will wait the specified
 195 time (in seconds) and then return, otherwise it will wait until something
 196 happens. Server returns T if something happened and NIL otherwise. Timeout
 197 0 means polling without waiting."
 198   (multiple-value-bind (to-sec to-usec stop-sec stop-usec signalp)
 199       (decode-timeout timeout)
 200     (declare (ignore stop-sec stop-usec))
 201     (sub-serve-event to-sec to-usec signalp)))
 202
 203 ;;; When a *periodic-polling-function* is defined the server will not
 204 ;;; block for more than the maximum event timeout and will call the
 205 ;;; polling function if it does time out.
 206 (declaim (type (or null symbol function) *periodic-polling-function*))
 207 (defvar *periodic-polling-function* nil
 208   "Either NIL, or a designator for a function callable without any
 209 arguments. Called when the system has been waiting for input for
 210 longer then *PERIODIC-POLLING-PERIOD* seconds. Shared between all
 211 threads, unless locally bound. EXPERIMENTAL.")
 212 (declaim (real *periodic-polling-period*))
 213 (defvar *periodic-polling-period* 0
 214   "A real number designating the number of seconds to wait for input
 215 at maximum, before calling the *PERIODIC-POLLING-FUNCTION* \(if any.)
 216 Shared between all threads, unless locally bound. EXPERIMENTAL.")
 217
 218 ;;; Takes timeout broken into seconds and microseconds, NIL timeout means
 219 ;;; to wait as long as needed.
 220 (defun sub-serve-event (to-sec to-usec deadlinep)
 221   (or
 222    (if *periodic-polling-function*
 223        (multiple-value-bind (p-sec p-usec)
 224            (decode-internal-time
 225             (seconds-to-internal-time *periodic-polling-period*))
 226          (if to-sec
 227              (loop repeat (/ (+ to-sec (/ to-usec 1e6))
 228                              *periodic-polling-period*)
 229                    thereis (sub-sub-serve-event p-sec p-usec)
 230                    do (funcall *periodic-polling-function*))
 231              (loop thereis (sub-sub-serve-event p-sec p-usec)
 232                    do (funcall *periodic-polling-function*))))
 233        (sub-sub-serve-event to-sec to-usec))
 234    (when deadlinep
 235      (signal-deadline))))
 236
 237 ;;; Handles the work of the above, except for periodic polling. Returns
 238 ;;; true if something of interest happened.
 239 (defun sub-sub-serve-event (to-sec to-usec)
 240   (sb!alien:with-alien ((read-fds (sb!alien:struct sb!unix:fd-set))
 241                         (write-fds (sb!alien:struct sb!unix:fd-set)))
 242     (sb!unix:fd-zero read-fds)
 243     (sb!unix:fd-zero write-fds)
 244     (let ((count 0))
 245       (declare (type index count))
 246
 247       ;; Initialize the fd-sets for UNIX-SELECT and return the active
 248       ;; descriptor count.
 249       (map-descriptor-handlers
 250        (lambda (handler)
 251          ;; FIXME: If HANDLER-ACTIVE ever is reinstanted, it needs
 252          ;; to be checked here in addition to HANDLER-BOGUS
 253          (unless (handler-bogus handler)
 254            (let ((fd (handler-descriptor handler)))
 255              (ecase (handler-direction handler)
 256                (:input (sb!unix:fd-set fd read-fds))
 257                (:output (sb!unix:fd-set fd write-fds)))
 258              (when (> fd count)
 259                (setf count fd))))))
 260       (incf count)
 261
 262       ;; Next, wait for something to happen.
 263       (multiple-value-bind (value err)
 264           (sb!unix:unix-fast-select count
 265                                     (sb!alien:addr read-fds)
 266                                     (sb!alien:addr write-fds)
 267                                     nil to-sec to-usec)
 268         #!+win32
 269         (declare (ignore err))
 270         ;; Now see what it was (if anything)
 271         (cond ((not value)
 272                ;; Interrupted or one of the file descriptors is bad.
 273                ;; FIXME: Check for other errnos. Why do we return true
 274                ;; when interrupted?
 275                #!-win32
 276                (if (eql err sb!unix:eintr)
 277                    t
 278                  (handler-descriptors-error))
 279                #!+win32
 280                (handler-descriptors-error))
 281               ((plusp value)
 282                ;; Got something. Call file descriptor handlers
 283                ;; according to the readable and writable masks
 284                ;; returned by select.
 285                (dolist (handler
 286                         (select-descriptor-handlers
 287                          (lambda (handler)
 288                            (let ((fd (handler-descriptor handler)))
 289                              (ecase (handler-direction handler)
 290                                (:input (sb!unix:fd-isset fd read-fds))
 291                                (:output (sb!unix:fd-isset fd write-fds)))))))
 292                  (funcall (handler-function handler)
 293                           (handler-descriptor handler)))
 294                t))))))
 295