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| 22 | <a href="./Home">MLton 20180207</a>\r |
| 23 | </div>\r |
| 24 | </div>\r |
| 25 | <div id="header">\r |
| 26 | <h1>MLtonSignal</h1>\r |
| 27 | </div>\r |
| 28 | <div id="content">\r |
| 29 | <div id="preamble">\r |
| 30 | <div class="sectionbody">\r |
| 31 | <div class="listingblock">\r |
| 32 | <div class="content"><div class="highlight"><pre><span class="k">signature</span><span class="w"> </span><span class="n">MLTON_SIGNAL</span><span class="w"> </span><span class="p">=</span><span class="w"></span>\r |
| 33 | <span class="w"> </span><span class="k">sig</span><span class="w"></span>\r |
| 34 | <span class="w"> </span><span class="k">type</span><span class="w"> </span><span class="n">t</span><span class="w"> </span><span class="p">=</span><span class="w"> </span><span class="n">Posix</span><span class="p">.</span><span class="n">Signal</span><span class="p">.</span><span class="n">signal</span><span class="w"></span>\r |
| 35 | <span class="w"> </span><span class="k">type</span><span class="w"> </span><span class="n">signal</span><span class="w"> </span><span class="p">=</span><span class="w"> </span><span class="n">t</span><span class="w"></span>\r |
| 36 | \r |
| 37 | <span class="w"> </span><span class="k">structure</span><span class="w"> </span><span class="n">Handler</span><span class="p">:</span><span class="w"></span>\r |
| 38 | <span class="w"> </span><span class="k">sig</span><span class="w"></span>\r |
| 39 | <span class="w"> </span><span class="k">type</span><span class="w"> </span><span class="n">t</span><span class="w"></span>\r |
| 40 | \r |
| 41 | <span class="w"> </span><span class="k">val</span><span class="w"> </span><span class="n">default</span><span class="p">:</span><span class="w"> </span><span class="n">t</span><span class="w"></span>\r |
| 42 | <span class="w"> </span><span class="k">val</span><span class="w"> </span><span class="n">handler</span><span class="p">:</span><span class="w"> </span><span class="p">(</span><span class="n">Thread</span><span class="p">.</span><span class="n">Runnable</span><span class="p">.</span><span class="n">t</span><span class="w"> </span><span class="p">-></span><span class="w"> </span><span class="n">Thread</span><span class="p">.</span><span class="n">Runnable</span><span class="p">.</span><span class="n">t</span><span class="p">)</span><span class="w"> </span><span class="p">-></span><span class="w"> </span><span class="n">t</span><span class="w"></span>\r |
| 43 | <span class="w"> </span><span class="k">val</span><span class="w"> </span><span class="n">ignore</span><span class="p">:</span><span class="w"> </span><span class="n">t</span><span class="w"></span>\r |
| 44 | <span class="w"> </span><span class="k">val</span><span class="w"> </span><span class="n">isDefault</span><span class="p">:</span><span class="w"> </span><span class="n">t</span><span class="w"> </span><span class="p">-></span><span class="w"> </span><span class="n">bool</span><span class="w"></span>\r |
| 45 | <span class="w"> </span><span class="k">val</span><span class="w"> </span><span class="n">isIgnore</span><span class="p">:</span><span class="w"> </span><span class="n">t</span><span class="w"> </span><span class="p">-></span><span class="w"> </span><span class="n">bool</span><span class="w"></span>\r |
| 46 | <span class="w"> </span><span class="k">val</span><span class="w"> </span><span class="n">simple</span><span class="p">:</span><span class="w"> </span><span class="p">(</span><span class="n">unit</span><span class="w"> </span><span class="p">-></span><span class="w"> </span><span class="n">unit</span><span class="p">)</span><span class="w"> </span><span class="p">-></span><span class="w"> </span><span class="n">t</span><span class="w"></span>\r |
| 47 | <span class="w"> </span><span class="k">end</span><span class="w"></span>\r |
| 48 | \r |
| 49 | <span class="w"> </span><span class="k">structure</span><span class="w"> </span><span class="n">Mask</span><span class="p">:</span><span class="w"></span>\r |
| 50 | <span class="w"> </span><span class="k">sig</span><span class="w"></span>\r |
| 51 | <span class="w"> </span><span class="k">type</span><span class="w"> </span><span class="n">t</span><span class="w"></span>\r |
| 52 | \r |
| 53 | <span class="w"> </span><span class="k">val</span><span class="w"> </span><span class="n">all</span><span class="p">:</span><span class="w"> </span><span class="n">t</span><span class="w"></span>\r |
| 54 | <span class="w"> </span><span class="k">val</span><span class="w"> </span><span class="n">allBut</span><span class="p">:</span><span class="w"> </span><span class="n">signal</span><span class="w"> </span><span class="n">list</span><span class="w"> </span><span class="p">-></span><span class="w"> </span><span class="n">t</span><span class="w"></span>\r |
| 55 | <span class="w"> </span><span class="k">val</span><span class="w"> </span><span class="n">block</span><span class="p">:</span><span class="w"> </span><span class="n">t</span><span class="w"> </span><span class="p">-></span><span class="w"> </span><span class="n">unit</span><span class="w"></span>\r |
| 56 | <span class="w"> </span><span class="k">val</span><span class="w"> </span><span class="n">getBlocked</span><span class="p">:</span><span class="w"> </span><span class="n">unit</span><span class="w"> </span><span class="p">-></span><span class="w"> </span><span class="n">t</span><span class="w"></span>\r |
| 57 | <span class="w"> </span><span class="k">val</span><span class="w"> </span><span class="n">isMember</span><span class="p">:</span><span class="w"> </span><span class="n">t</span><span class="w"> </span><span class="n">*</span><span class="w"> </span><span class="n">signal</span><span class="w"> </span><span class="p">-></span><span class="w"> </span><span class="n">bool</span><span class="w"></span>\r |
| 58 | <span class="w"> </span><span class="k">val</span><span class="w"> </span><span class="n">none</span><span class="p">:</span><span class="w"> </span><span class="n">t</span><span class="w"></span>\r |
| 59 | <span class="w"> </span><span class="k">val</span><span class="w"> </span><span class="n">setBlocked</span><span class="p">:</span><span class="w"> </span><span class="n">t</span><span class="w"> </span><span class="p">-></span><span class="w"> </span><span class="n">unit</span><span class="w"></span>\r |
| 60 | <span class="w"> </span><span class="k">val</span><span class="w"> </span><span class="n">some</span><span class="p">:</span><span class="w"> </span><span class="n">signal</span><span class="w"> </span><span class="n">list</span><span class="w"> </span><span class="p">-></span><span class="w"> </span><span class="n">t</span><span class="w"></span>\r |
| 61 | <span class="w"> </span><span class="k">val</span><span class="w"> </span><span class="n">unblock</span><span class="p">:</span><span class="w"> </span><span class="n">t</span><span class="w"> </span><span class="p">-></span><span class="w"> </span><span class="n">unit</span><span class="w"></span>\r |
| 62 | <span class="w"> </span><span class="k">end</span><span class="w"></span>\r |
| 63 | \r |
| 64 | <span class="w"> </span><span class="k">val</span><span class="w"> </span><span class="n">getHandler</span><span class="p">:</span><span class="w"> </span><span class="n">t</span><span class="w"> </span><span class="p">-></span><span class="w"> </span><span class="n">Handler</span><span class="p">.</span><span class="n">t</span><span class="w"></span>\r |
| 65 | <span class="w"> </span><span class="k">val</span><span class="w"> </span><span class="n">handled</span><span class="p">:</span><span class="w"> </span><span class="n">unit</span><span class="w"> </span><span class="p">-></span><span class="w"> </span><span class="n">Mask</span><span class="p">.</span><span class="n">t</span><span class="w"></span>\r |
| 66 | <span class="w"> </span><span class="k">val</span><span class="w"> </span><span class="n">prof</span><span class="p">:</span><span class="w"> </span><span class="n">t</span><span class="w"></span>\r |
| 67 | <span class="w"> </span><span class="k">val</span><span class="w"> </span><span class="n">restart</span><span class="p">:</span><span class="w"> </span><span class="n">bool</span><span class="w"> </span><span class="n">ref</span><span class="w"></span>\r |
| 68 | <span class="w"> </span><span class="k">val</span><span class="w"> </span><span class="n">setHandler</span><span class="p">:</span><span class="w"> </span><span class="n">t</span><span class="w"> </span><span class="n">*</span><span class="w"> </span><span class="n">Handler</span><span class="p">.</span><span class="n">t</span><span class="w"> </span><span class="p">-></span><span class="w"> </span><span class="n">unit</span><span class="w"></span>\r |
| 69 | <span class="w"> </span><span class="k">val</span><span class="w"> </span><span class="n">suspend</span><span class="p">:</span><span class="w"> </span><span class="n">Mask</span><span class="p">.</span><span class="n">t</span><span class="w"> </span><span class="p">-></span><span class="w"> </span><span class="n">unit</span><span class="w"></span>\r |
| 70 | <span class="w"> </span><span class="k">val</span><span class="w"> </span><span class="n">vtalrm</span><span class="p">:</span><span class="w"> </span><span class="n">t</span><span class="w"></span>\r |
| 71 | <span class="w"> </span><span class="k">end</span><span class="w"></span>\r |
| 72 | </pre></div></div></div>\r |
| 73 | <div class="paragraph"><p>Signals handlers are functions from (runnable) threads to (runnable)\r |
| 74 | threads. When a signal arrives, the corresponding signal handler is\r |
| 75 | invoked, its argument being the thread that was interrupted by the\r |
| 76 | signal. The signal handler runs asynchronously, in its own thread.\r |
| 77 | The signal handler returns the thread that it would like to resume\r |
| 78 | execution (this is often the thread that it was passed). It is an\r |
| 79 | error for a signal handler to raise an exception that is not handled\r |
| 80 | within the signal handler itself.</p></div>\r |
| 81 | <div class="paragraph"><p>A signal handler is never invoked while the running thread is in a\r |
| 82 | critical section (see <a href="MLtonThread">MLtonThread</a>). Invoking a signal handler\r |
| 83 | implicitly enters a critical section and the normal return of a signal\r |
| 84 | handler implicitly exits the critical section; hence, a signal handler\r |
| 85 | is never interrupted by another signal handler.</p></div>\r |
| 86 | <div class="ulist"><ul>\r |
| 87 | <li>\r |
| 88 | <p>\r |
| 89 | <span class="monospaced">type t</span>\r |
| 90 | </p>\r |
| 91 | <div class="paragraph"><p>the type of signals.</p></div>\r |
| 92 | </li>\r |
| 93 | <li>\r |
| 94 | <p>\r |
| 95 | <span class="monospaced">type Handler.t</span>\r |
| 96 | </p>\r |
| 97 | <div class="paragraph"><p>the type of signal handlers.</p></div>\r |
| 98 | </li>\r |
| 99 | <li>\r |
| 100 | <p>\r |
| 101 | <span class="monospaced">Handler.default</span>\r |
| 102 | </p>\r |
| 103 | <div class="paragraph"><p>handles the signal with the default action.</p></div>\r |
| 104 | </li>\r |
| 105 | <li>\r |
| 106 | <p>\r |
| 107 | <span class="monospaced">Handler.handler f</span>\r |
| 108 | </p>\r |
| 109 | <div class="paragraph"><p>returns a handler <span class="monospaced">h</span> such that when a signal <span class="monospaced">s</span> is handled by <span class="monospaced">h</span>,\r |
| 110 | <span class="monospaced">f</span> will be passed the thread that was interrupted by <span class="monospaced">s</span> and should\r |
| 111 | return the thread that will resume execution.</p></div>\r |
| 112 | </li>\r |
| 113 | <li>\r |
| 114 | <p>\r |
| 115 | <span class="monospaced">Handler.ignore</span>\r |
| 116 | </p>\r |
| 117 | <div class="paragraph"><p>is a handler that will ignore the signal.</p></div>\r |
| 118 | </li>\r |
| 119 | <li>\r |
| 120 | <p>\r |
| 121 | <span class="monospaced">Handler.isDefault</span>\r |
| 122 | </p>\r |
| 123 | <div class="paragraph"><p>returns true if the handler is the default handler.</p></div>\r |
| 124 | </li>\r |
| 125 | <li>\r |
| 126 | <p>\r |
| 127 | <span class="monospaced">Handler.isIgnore</span>\r |
| 128 | </p>\r |
| 129 | <div class="paragraph"><p>returns true if the handler is the ignore handler.</p></div>\r |
| 130 | </li>\r |
| 131 | <li>\r |
| 132 | <p>\r |
| 133 | <span class="monospaced">Handler.simple f</span>\r |
| 134 | </p>\r |
| 135 | <div class="paragraph"><p>returns a handler that executes <span class="monospaced">f ()</span> and does not switch threads.</p></div>\r |
| 136 | </li>\r |
| 137 | <li>\r |
| 138 | <p>\r |
| 139 | <span class="monospaced">type Mask.t</span>\r |
| 140 | </p>\r |
| 141 | <div class="paragraph"><p>the type of signal masks, which are sets of blocked signals.</p></div>\r |
| 142 | </li>\r |
| 143 | <li>\r |
| 144 | <p>\r |
| 145 | <span class="monospaced">Mask.all</span>\r |
| 146 | </p>\r |
| 147 | <div class="paragraph"><p>a mask of all signals.</p></div>\r |
| 148 | </li>\r |
| 149 | <li>\r |
| 150 | <p>\r |
| 151 | <span class="monospaced">Mask.allBut l</span>\r |
| 152 | </p>\r |
| 153 | <div class="paragraph"><p>a mask of all signals except for those in <span class="monospaced">l</span>.</p></div>\r |
| 154 | </li>\r |
| 155 | <li>\r |
| 156 | <p>\r |
| 157 | <span class="monospaced">Mask.block m</span>\r |
| 158 | </p>\r |
| 159 | <div class="paragraph"><p>blocks all signals in <span class="monospaced">m</span>.</p></div>\r |
| 160 | </li>\r |
| 161 | <li>\r |
| 162 | <p>\r |
| 163 | <span class="monospaced">Mask.getBlocked ()</span>\r |
| 164 | </p>\r |
| 165 | <div class="paragraph"><p>gets the signal mask <span class="monospaced">m</span>, i.e. a signal is blocked if and only if it\r |
| 166 | is in <span class="monospaced">m</span>.</p></div>\r |
| 167 | </li>\r |
| 168 | <li>\r |
| 169 | <p>\r |
| 170 | <span class="monospaced">Mask.isMember (m, s)</span>\r |
| 171 | </p>\r |
| 172 | <div class="paragraph"><p>returns true if the signal <span class="monospaced">s</span> is in <span class="monospaced">m</span>.</p></div>\r |
| 173 | </li>\r |
| 174 | <li>\r |
| 175 | <p>\r |
| 176 | <span class="monospaced">Mask.none</span>\r |
| 177 | </p>\r |
| 178 | <div class="paragraph"><p>a mask of no signals.</p></div>\r |
| 179 | </li>\r |
| 180 | <li>\r |
| 181 | <p>\r |
| 182 | <span class="monospaced">Mask.setBlocked m</span>\r |
| 183 | </p>\r |
| 184 | <div class="paragraph"><p>sets the signal mask to <span class="monospaced">m</span>, i.e. a signal is blocked if and only if\r |
| 185 | it is in <span class="monospaced">m</span>.</p></div>\r |
| 186 | </li>\r |
| 187 | <li>\r |
| 188 | <p>\r |
| 189 | <span class="monospaced">Mask.some l</span>\r |
| 190 | </p>\r |
| 191 | <div class="paragraph"><p>a mask of the signals in <span class="monospaced">l</span>.</p></div>\r |
| 192 | </li>\r |
| 193 | <li>\r |
| 194 | <p>\r |
| 195 | <span class="monospaced">Mask.unblock m</span>\r |
| 196 | </p>\r |
| 197 | <div class="paragraph"><p>unblocks all signals in <span class="monospaced">m</span>.</p></div>\r |
| 198 | </li>\r |
| 199 | <li>\r |
| 200 | <p>\r |
| 201 | <span class="monospaced">getHandler s</span>\r |
| 202 | </p>\r |
| 203 | <div class="paragraph"><p>returns the current handler for signal <span class="monospaced">s</span>.</p></div>\r |
| 204 | </li>\r |
| 205 | <li>\r |
| 206 | <p>\r |
| 207 | <span class="monospaced">handled ()</span>\r |
| 208 | </p>\r |
| 209 | <div class="paragraph"><p>returns the signal mask <span class="monospaced">m</span> corresponding to the currently handled\r |
| 210 | signals; i.e., a signal is handled if and only if it is in <span class="monospaced">m</span>.</p></div>\r |
| 211 | </li>\r |
| 212 | <li>\r |
| 213 | <p>\r |
| 214 | <span class="monospaced">prof</span>\r |
| 215 | </p>\r |
| 216 | <div class="paragraph"><p><span class="monospaced">SIGPROF</span>, the profiling signal.</p></div>\r |
| 217 | </li>\r |
| 218 | <li>\r |
| 219 | <p>\r |
| 220 | <span class="monospaced">restart</span>\r |
| 221 | </p>\r |
| 222 | <div class="paragraph"><p>dynamically determines the behavior of interrupted system calls; when\r |
| 223 | <span class="monospaced">true</span>, interrupted system calls are restarted; when <span class="monospaced">false</span>,\r |
| 224 | interrupted system calls raise <span class="monospaced">OS.SysError</span>.</p></div>\r |
| 225 | </li>\r |
| 226 | <li>\r |
| 227 | <p>\r |
| 228 | <span class="monospaced">setHandler (s, h)</span>\r |
| 229 | </p>\r |
| 230 | <div class="paragraph"><p>sets the handler for signal <span class="monospaced">s</span> to <span class="monospaced">h</span>.</p></div>\r |
| 231 | </li>\r |
| 232 | <li>\r |
| 233 | <p>\r |
| 234 | <span class="monospaced">suspend m</span>\r |
| 235 | </p>\r |
| 236 | <div class="paragraph"><p>temporarily sets the signal mask to <span class="monospaced">m</span> and suspends until an unmasked\r |
| 237 | signal is received and handled, at which point <span class="monospaced">suspend</span> resets the\r |
| 238 | mask and returns.</p></div>\r |
| 239 | </li>\r |
| 240 | <li>\r |
| 241 | <p>\r |
| 242 | <span class="monospaced">vtalrm</span>\r |
| 243 | </p>\r |
| 244 | <div class="paragraph"><p><span class="monospaced">SIGVTALRM</span>, the signal for virtual timers.</p></div>\r |
| 245 | </li>\r |
| 246 | </ul></div>\r |
| 247 | </div>\r |
| 248 | </div>\r |
| 249 | <div class="sect1">\r |
| 250 | <h2 id="_interruptible_system_calls">Interruptible System Calls</h2>\r |
| 251 | <div class="sectionbody">\r |
| 252 | <div class="paragraph"><p>Signal handling interacts in a non-trivial way with those functions in\r |
| 253 | the <a href="BasisLibrary">Basis Library</a> that correspond directly to\r |
| 254 | interruptible system calls (a subset of those functions that may raise\r |
| 255 | <span class="monospaced">OS.SysError</span>). The desire is that these functions should have\r |
| 256 | predictable semantics. The principal concerns are:</p></div>\r |
| 257 | <div class="olist arabic"><ol class="arabic">\r |
| 258 | <li>\r |
| 259 | <p>\r |
| 260 | System calls that are interrupted by signals should, by default, be\r |
| 261 | restarted; the alternative is to raise\r |
| 262 | </p>\r |
| 263 | <div class="listingblock">\r |
| 264 | <div class="content"><div class="highlight"><pre><span class="n">OS</span><span class="p">.</span><span class="n">SysError</span><span class="w"> </span><span class="p">(</span><span class="n">Posix</span><span class="p">.</span><span class="n">Error</span><span class="p">.</span><span class="n">errorMsg</span><span class="w"> </span><span class="n">Posix</span><span class="p">.</span><span class="n">Error</span><span class="p">.</span><span class="n">intr</span><span class="p">,</span><span class="w"></span>\r |
| 265 | <span class="w"> </span><span class="n">SOME</span><span class="w"> </span><span class="n">Posix</span><span class="p">.</span><span class="n">Error</span><span class="p">.</span><span class="n">intr</span><span class="p">)</span><span class="w"></span>\r |
| 266 | </pre></div></div></div>\r |
| 267 | <div class="paragraph"><p>This behavior is determined dynamically by the value of <span class="monospaced">Signal.restart</span>.</p></div>\r |
| 268 | </li>\r |
| 269 | <li>\r |
| 270 | <p>\r |
| 271 | Signal handlers should always get a chance to run (when outside a\r |
| 272 | critical region). If a system call is interrupted by a signal, then\r |
| 273 | the signal handler will run before the call is restarted or\r |
| 274 | <span class="monospaced">OS.SysError</span> is raised; that is, before the <span class="monospaced">Signal.restart</span> check.\r |
| 275 | </p>\r |
| 276 | </li>\r |
| 277 | <li>\r |
| 278 | <p>\r |
| 279 | A system call that must be restarted while in a critical section\r |
| 280 | will be restarted with the handled signals blocked (and the previously\r |
| 281 | blocked signals remembered). This encourages the system call to\r |
| 282 | complete, allowing the program to make progress towards leaving the\r |
| 283 | critical section where the signal can be handled. If the system call\r |
| 284 | completes, the set of blocked signals are restored to those previously\r |
| 285 | blocked.\r |
| 286 | </p>\r |
| 287 | </li>\r |
| 288 | </ol></div>\r |
| 289 | </div>\r |
| 290 | </div>\r |
| 291 | </div>\r |
| 292 | <div id="footnotes"><hr></div>\r |
| 293 | <div id="footer">\r |
| 294 | <div id="footer-text">\r |
| 295 | </div>\r |
| 296 | <div id="footer-badges">\r |
| 297 | </div>\r |
| 298 | </div>\r |
| 299 | </body>\r |
| 300 | </html>\r |