iokit/Kernel/IOWorkLoop.cpp

   1 /*
   2  * Copyright (c) 1998-2010 Apple Inc. All rights reserved.
   3  *
   4  * @APPLE_OSREFERENCE_LICENSE_HEADER_START@
   5  *
   6  * This file contains Original Code and/or Modifications of Original Code
   7  * as defined in and that are subject to the Apple Public Source License
   8  * Version 2.0 (the 'License'). You may not use this file except in
   9  * compliance with the License. The rights granted to you under the License
  10  * may not be used to create, or enable the creation or redistribution of,
  11  * unlawful or unlicensed copies of an Apple operating system, or to
  12  * circumvent, violate, or enable the circumvention or violation of, any
  13  * terms of an Apple operating system software license agreement.
  14  *
  15  * Please obtain a copy of the License at
  16  * http://www.opensource.apple.com/apsl/ and read it before using this file.
  17  *
  18  * The Original Code and all software distributed under the License are
  19  * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
  20  * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
  21  * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
  22  * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
  23  * Please see the License for the specific language governing rights and
  24  * limitations under the License.
  25  *
  26  * @APPLE_OSREFERENCE_LICENSE_HEADER_END@
  27  */
  28
  29 #include <pexpert/pexpert.h>
  30 #include <IOKit/IOWorkLoop.h>
  31 #include <IOKit/IOEventSource.h>
  32 #include <IOKit/IOInterruptEventSource.h>
  33 #include <IOKit/IOCommandGate.h>
  34 #include <IOKit/IOTimeStamp.h>
  35 #include <IOKit/IOKitDebug.h>
  36 #include <libkern/OSDebug.h>
  37 #include <kern/thread.h>
  38
  39 #define super OSObject
  40
  41 OSDefineMetaClassAndStructors(IOWorkLoop, OSObject);
  42
  43 // Block of unused functions intended for future use
  44 #if __LP64__
  45 OSMetaClassDefineReservedUnused(IOWorkLoop, 0);
  46 OSMetaClassDefineReservedUnused(IOWorkLoop, 1);
  47 OSMetaClassDefineReservedUnused(IOWorkLoop, 2);
  48 #else
  49 OSMetaClassDefineReservedUsed(IOWorkLoop, 0);
  50 OSMetaClassDefineReservedUsed(IOWorkLoop, 1);
  51 OSMetaClassDefineReservedUsed(IOWorkLoop, 2);
  52 #endif
  53 OSMetaClassDefineReservedUnused(IOWorkLoop, 3);
  54 OSMetaClassDefineReservedUnused(IOWorkLoop, 4);
  55 OSMetaClassDefineReservedUnused(IOWorkLoop, 5);
  56 OSMetaClassDefineReservedUnused(IOWorkLoop, 6);
  57 OSMetaClassDefineReservedUnused(IOWorkLoop, 7);
  58
  59 enum IOWorkLoopState { kLoopRestart = 0x1, kLoopTerminate = 0x2 };
  60 static inline void SETP(void *addr, unsigned int flag)
  61     { unsigned char *num = (unsigned char *) addr; *num |= flag; }
  62 static inline void CLRP(void *addr, unsigned int flag)
  63     { unsigned char *num = (unsigned char *) addr; *num &= ~flag; }
  64 static inline bool ISSETP(void *addr, unsigned int flag)
  65     { unsigned char *num = (unsigned char *) addr; return (*num & flag) != 0; }
  66
  67 #define fFlags loopRestart
  68
  69 #define passiveEventChain       reserved->passiveEventChain
  70
  71 #if IOKITSTATS
  72
  73 #define IOStatisticsRegisterCounter() \
  74 do { \
  75         reserved->counter = IOStatistics::registerWorkLoop(this); \
  76 } while(0)
  77
  78 #define IOStatisticsUnregisterCounter() \
  79 do { \
  80         if (reserved) \
  81                 IOStatistics::unregisterWorkLoop(reserved->counter); \
  82 } while(0)
  83
  84 #define IOStatisticsOpenGate() \
  85 do { \
  86         IOStatistics::countWorkLoopOpenGate(reserved->counter); \
  87 } while(0)
  88
  89 #define IOStatisticsCloseGate() \
  90 do { \
  91         IOStatistics::countWorkLoopCloseGate(reserved->counter); \
  92 } while(0)
  93
  94 #define IOStatisticsAttachEventSource() \
  95 do { \
  96         IOStatistics::attachWorkLoopEventSource(reserved->counter, inEvent->reserved->counter); \
  97 } while(0)
  98
  99 #define IOStatisticsDetachEventSource() \
 100 do { \
 101         IOStatistics::detachWorkLoopEventSource(reserved->counter, inEvent->reserved->counter); \
 102 } while(0)
 103
 104 #else
 105
 106 #define IOStatisticsRegisterCounter()
 107 #define IOStatisticsUnregisterCounter()
 108 #define IOStatisticsOpenGate()
 109 #define IOStatisticsCloseGate()
 110 #define IOStatisticsAttachEventSource()
 111 #define IOStatisticsDetachEventSource()
 112
 113 #endif /* IOKITSTATS */
 114
 115 bool IOWorkLoop::init()
 116 {
 117     // The super init and gateLock allocation MUST be done first.
 118     if ( !super::init() )
 119         return false;
 120
 121         // Allocate our ExpansionData if it hasn't been allocated already.
 122         if ( !reserved )
 123         {
 124                 reserved = IONew(ExpansionData,1);
 125                 if ( !reserved )
 126                         return false;
 127
 128                 bzero(reserved,sizeof(ExpansionData));
 129         }
 130
 131 #if DEBUG
 132         OSBacktrace ( reserved->allocationBacktrace, sizeof ( reserved->allocationBacktrace ) / sizeof ( reserved->allocationBacktrace[0] ) );
 133 #endif
 134
 135     if ( gateLock == NULL ) {
 136         if ( !( gateLock = IORecursiveLockAlloc()) )
 137             return false;
 138     }
 139
 140     if ( workToDoLock == NULL ) {
 141         if ( !(workToDoLock = IOSimpleLockAlloc()) )
 142             return false;
 143         IOSimpleLockInit(workToDoLock);
 144         workToDo = false;
 145     }
 146
 147     IOStatisticsRegisterCounter();
 148
 149     if ( controlG == NULL ) {
 150         controlG = IOCommandGate::commandGate(
 151             this,
 152             OSMemberFunctionCast(
 153                 IOCommandGate::Action,
 154                 this,
 155                 &IOWorkLoop::_maintRequest));
 156
 157         if ( !controlG )
 158             return false;
 159         // Point the controlGate at the workLoop.  Usually addEventSource
 160         // does this automatically.  The problem is in this case addEventSource
 161         // uses the control gate and it has to be bootstrapped.
 162         controlG->setWorkLoop(this);
 163         if (addEventSource(controlG) != kIOReturnSuccess)
 164             return false;
 165     }
 166
 167     if ( workThread == NULL ) {
 168         thread_continue_t cptr = OSMemberFunctionCast(
 169             thread_continue_t,
 170             this,
 171             &IOWorkLoop::threadMain);
 172         if (KERN_SUCCESS != kernel_thread_start(cptr, this, &workThread))
 173             return false;
 174     }
 175
 176     (void) thread_set_tag(workThread, THREAD_TAG_IOWORKLOOP);
 177     return true;
 178 }
 179
 180 IOWorkLoop *
 181 IOWorkLoop::workLoop()
 182 {
 183     return IOWorkLoop::workLoopWithOptions(0);
 184 }
 185
 186 IOWorkLoop *
 187 IOWorkLoop::workLoopWithOptions(IOOptionBits options)
 188 {
 189         IOWorkLoop *me = new IOWorkLoop;
 190
 191         if (me && options) {
 192                 me->reserved = IONew(ExpansionData,1);
 193                 if (!me->reserved) {
 194                         me->release();
 195                         return 0;
 196                 }
 197                 bzero(me->reserved,sizeof(ExpansionData));
 198                 me->reserved->options = options;
 199         }
 200
 201         if (me && !me->init()) {
 202                 me->release();
 203                 return 0;
 204         }
 205
 206         return me;
 207 }
 208
 209 // Free is called twice:
 210 // First when the atomic retainCount transitions from 1 -> 0
 211 // Secondly when the work loop itself is commiting hari kari
 212 // Hence the each leg of the free must be single threaded.
 213 void IOWorkLoop::free()
 214 {
 215     if (workThread) {
 216         IOInterruptState is;
 217
 218         // If we are here then we must be trying to shut down this work loop
 219         // in this case disable all of the event source, mark the loop
 220         // as terminating and wakeup the work thread itself and return
 221         // Note: we hold the gate across the entire operation mainly for the
 222         // benefit of our event sources so we can disable them cleanly.
 223         closeGate();
 224
 225         disableAllEventSources();
 226
 227         is = IOSimpleLockLockDisableInterrupt(workToDoLock);
 228         SETP(&fFlags, kLoopTerminate);
 229         thread_wakeup_one((void *) &workToDo);
 230         IOSimpleLockUnlockEnableInterrupt(workToDoLock, is);
 231
 232         openGate();
 233     }
 234     else /* !workThread */ {
 235         IOEventSource *event, *next;
 236
 237         for (event = eventChain; event; event = next) {
 238             next = event->getNext();
 239             event->setWorkLoop(0);
 240             event->setNext(0);
 241             event->release();
 242         }
 243         eventChain = 0;
 244
 245         for (event = passiveEventChain; event; event = next) {
 246             next = event->getNext();
 247             event->setWorkLoop(0);
 248             event->setNext(0);
 249             event->release();
 250         }
 251         passiveEventChain = 0;
 252
 253         // Either we have a partial initialization to clean up
 254         // or the workThread itself is performing hari-kari.
 255         // Either way clean up all of our resources and return.
 256
 257         if (controlG) {
 258             controlG->release();
 259             controlG = 0;
 260         }
 261
 262         if (workToDoLock) {
 263             IOSimpleLockFree(workToDoLock);
 264             workToDoLock = 0;
 265         }
 266
 267         if (gateLock) {
 268             IORecursiveLockFree(gateLock);
 269             gateLock = 0;
 270         }
 271
 272         IOStatisticsUnregisterCounter();
 273
 274         if (reserved) {
 275             IODelete(reserved, ExpansionData, 1);
 276             reserved = 0;
 277         }
 278
 279         super::free();
 280     }
 281 }
 282
 283 IOReturn IOWorkLoop::addEventSource(IOEventSource *newEvent)
 284 {
 285     return controlG->runCommand((void *) mAddEvent, (void *) newEvent);
 286 }
 287
 288 IOReturn IOWorkLoop::removeEventSource(IOEventSource *toRemove)
 289 {
 290     return controlG->runCommand((void *) mRemoveEvent, (void *) toRemove);
 291 }
 292
 293 void IOWorkLoop::enableAllEventSources() const
 294 {
 295     IOEventSource *event;
 296
 297     for (event = eventChain; event; event = event->getNext())
 298         event->enable();
 299
 300     for (event = passiveEventChain; event; event = event->getNext())
 301         event->enable();
 302 }
 303
 304 void IOWorkLoop::disableAllEventSources() const
 305 {
 306     IOEventSource *event;
 307
 308     for (event = eventChain; event; event = event->getNext())
 309                 event->disable();
 310
 311         /* NOTE: controlG is in passiveEventChain since it's an IOCommandGate */
 312     for (event = passiveEventChain; event; event = event->getNext())
 313         if (event != controlG)  // Don't disable the control gate
 314             event->disable();
 315 }
 316
 317 void IOWorkLoop::enableAllInterrupts() const
 318 {
 319     IOEventSource *event;
 320
 321     for (event = eventChain; event; event = event->getNext())
 322         if (OSDynamicCast(IOInterruptEventSource, event))
 323             event->enable();
 324 }
 325
 326 void IOWorkLoop::disableAllInterrupts() const
 327 {
 328     IOEventSource *event;
 329
 330     for (event = eventChain; event; event = event->getNext())
 331         if (OSDynamicCast(IOInterruptEventSource, event))
 332             event->disable();
 333 }
 334
 335
 336 /* virtual */ bool IOWorkLoop::runEventSources()
 337 {
 338     bool res = false;
 339     bool traceWL = (gIOKitTrace & kIOTraceWorkLoops) ? true : false;
 340     bool traceES = (gIOKitTrace & kIOTraceEventSources) ? true : false;
 341
 342     closeGate();
 343     if (ISSETP(&fFlags, kLoopTerminate))
 344                 goto abort;
 345
 346     if (traceWL)
 347         IOTimeStampStartConstant(IODBG_WORKLOOP(IOWL_WORK), (uintptr_t) this);
 348
 349     bool more;
 350     do {
 351                 CLRP(&fFlags, kLoopRestart);
 352                 more = false;
 353                 IOInterruptState is = IOSimpleLockLockDisableInterrupt(workToDoLock);
 354                 workToDo = false;
 355                 IOSimpleLockUnlockEnableInterrupt(workToDoLock, is);
 356                 /* NOTE: only loop over event sources in eventChain. Bypass "passive" event sources for performance */
 357                 for (IOEventSource *evnt = eventChain; evnt; evnt = evnt->getNext()) {
 358
 359                         if (traceES)
 360                                 IOTimeStampStartConstant(IODBG_WORKLOOP(IOWL_CLIENT), (uintptr_t) this, (uintptr_t) evnt);
 361
 362                         more |= evnt->checkForWork();
 363
 364                         if (traceES)
 365                                 IOTimeStampEndConstant(IODBG_WORKLOOP(IOWL_CLIENT), (uintptr_t) this, (uintptr_t) evnt);
 366
 367                         if (ISSETP(&fFlags, kLoopTerminate))
 368                                 goto abort;
 369                         else if (fFlags & kLoopRestart) {
 370                                 more = true;
 371                                 break;
 372                         }
 373                 }
 374     } while (more);
 375
 376     res = true;
 377
 378     if (traceWL)
 379         IOTimeStampEndConstant(IODBG_WORKLOOP(IOWL_WORK), (uintptr_t) this);
 380
 381 abort:
 382     openGate();
 383     return res;
 384 }
 385
 386 /* virtual */ void IOWorkLoop::threadMain()
 387 {
 388 restartThread:
 389     do {
 390         if ( !runEventSources() )
 391             goto exitThread;
 392
 393         IOInterruptState is = IOSimpleLockLockDisableInterrupt(workToDoLock);
 394         if ( !ISSETP(&fFlags, kLoopTerminate) && !workToDo) {
 395             assert_wait((void *) &workToDo, false);
 396             IOSimpleLockUnlockEnableInterrupt(workToDoLock, is);
 397             thread_continue_t cptr = NULL;
 398             if (!reserved || !(kPreciousStack & reserved->options))
 399                 cptr = OSMemberFunctionCast(
 400                         thread_continue_t, this, &IOWorkLoop::threadMain);
 401             thread_block_parameter(cptr, this);
 402             goto restartThread;
 403             /* NOTREACHED */
 404         }
 405
 406         // At this point we either have work to do or we need
 407         // to commit suicide.  But no matter
 408         // Clear the simple lock and retore the interrupt state
 409         IOSimpleLockUnlockEnableInterrupt(workToDoLock, is);
 410     } while(workToDo);
 411
 412 exitThread:
 413         thread_t thread = workThread;
 414     workThread = 0;     // Say we don't have a loop and free ourselves
 415     free();
 416
 417         thread_deallocate(thread);
 418     (void) thread_terminate(thread);
 419 }
 420
 421 IOThread IOWorkLoop::getThread() const
 422 {
 423     return workThread;
 424 }
 425
 426 bool IOWorkLoop::onThread() const
 427 {
 428     return (IOThreadSelf() == workThread);
 429 }
 430
 431 bool IOWorkLoop::inGate() const
 432 {
 433     return IORecursiveLockHaveLock(gateLock);
 434 }
 435
 436 // Internal APIs used by event sources to control the thread
 437 void IOWorkLoop::signalWorkAvailable()
 438 {
 439     if (workToDoLock) {
 440         IOInterruptState is = IOSimpleLockLockDisableInterrupt(workToDoLock);
 441         workToDo = true;
 442         thread_wakeup_one((void *) &workToDo);
 443         IOSimpleLockUnlockEnableInterrupt(workToDoLock, is);
 444     }
 445 }
 446
 447 void IOWorkLoop::openGate()
 448 {
 449     IOStatisticsOpenGate();
 450     IORecursiveLockUnlock(gateLock);
 451 }
 452
 453 void IOWorkLoop::closeGate()
 454 {
 455     IORecursiveLockLock(gateLock);
 456     IOStatisticsCloseGate();
 457 }
 458
 459 bool IOWorkLoop::tryCloseGate()
 460 {
 461     bool res = (IORecursiveLockTryLock(gateLock) != 0);
 462     if (res) {
 463         IOStatisticsCloseGate();
 464     }
 465     return res;
 466 }
 467
 468 int IOWorkLoop::sleepGate(void *event, UInt32 interuptibleType)
 469 {
 470     int res;
 471     IOStatisticsOpenGate();
 472     res = IORecursiveLockSleep(gateLock, event, interuptibleType);
 473     IOStatisticsCloseGate();
 474     return res;
 475 }
 476
 477 int IOWorkLoop::sleepGate(void *event, AbsoluteTime deadline, UInt32 interuptibleType)
 478 {
 479     int res;
 480     IOStatisticsOpenGate();
 481     res = IORecursiveLockSleepDeadline(gateLock, event, deadline, interuptibleType);
 482     IOStatisticsCloseGate();
 483     return res;
 484 }
 485
 486 void IOWorkLoop::wakeupGate(void *event, bool oneThread)
 487 {
 488     IORecursiveLockWakeup(gateLock, event, oneThread);
 489 }
 490
 491 IOReturn IOWorkLoop::runAction(Action inAction, OSObject *target,
 492                                   void *arg0, void *arg1,
 493                                   void *arg2, void *arg3)
 494 {
 495     IOReturn res;
 496
 497     // closeGate is recursive so don't worry if we already hold the lock.
 498     closeGate();
 499     res = (*inAction)(target, arg0, arg1, arg2, arg3);
 500     openGate();
 501
 502     return res;
 503 }
 504
 505 IOReturn IOWorkLoop::_maintRequest(void *inC, void *inD, void *, void *)
 506 {
 507     maintCommandEnum command = (maintCommandEnum) (uintptr_t) inC;
 508     IOEventSource *inEvent = (IOEventSource *) inD;
 509     IOReturn res = kIOReturnSuccess;
 510
 511     switch (command)
 512     {
 513     case mAddEvent:
 514         if (!inEvent->getWorkLoop()) {
 515             SETP(&fFlags, kLoopRestart);
 516
 517             inEvent->retain();
 518             inEvent->setWorkLoop(this);
 519             inEvent->setNext(0);
 520
 521                 /* Check if this is a passive or active event source being added */
 522                 if (eventSourcePerformsWork(inEvent)) {
 523
 524                     if (!eventChain)
 525                     eventChain = inEvent;
 526                     else {
 527                     IOEventSource *event, *next;
 528
 529                         for (event = eventChain; (next = event->getNext()); event = next)
 530                         ;
 531                         event->setNext(inEvent);
 532
 533                 }
 534
 535             }
 536             else {
 537
 538                     if (!passiveEventChain)
 539                     passiveEventChain = inEvent;
 540                     else {
 541                     IOEventSource *event, *next;
 542
 543                         for (event = passiveEventChain; (next = event->getNext()); event = next)
 544                         ;
 545                         event->setNext(inEvent);
 546
 547                 }
 548
 549             }
 550             IOStatisticsAttachEventSource();
 551         }
 552         break;
 553
 554     case mRemoveEvent:
 555         if (inEvent->getWorkLoop()) {
 556                 IOStatisticsDetachEventSource();
 557
 558                 if (eventSourcePerformsWork(inEvent)) {
 559                                 if (eventChain == inEvent)
 560                                         eventChain = inEvent->getNext();
 561                                 else {
 562                                         IOEventSource *event, *next;
 563
 564                                         event = eventChain;
 565                                         while ((next = event->getNext()) && next != inEvent)
 566                                                 event = next;
 567
 568                                         if (!next) {
 569                                                 res = kIOReturnBadArgument;
 570                                                 break;
 571                                         }
 572                                         event->setNext(inEvent->getNext());
 573                                 }
 574                 }
 575                 else {
 576                                 if (passiveEventChain == inEvent)
 577                                         passiveEventChain = inEvent->getNext();
 578                                 else {
 579                                         IOEventSource *event, *next;
 580
 581                                         event = passiveEventChain;
 582                                         while ((next = event->getNext()) && next != inEvent)
 583                                                 event = next;
 584
 585                                         if (!next) {
 586                                                 res = kIOReturnBadArgument;
 587                                                 break;
 588                                         }
 589                                         event->setNext(inEvent->getNext());
 590                                 }
 591                 }
 592
 593             inEvent->setWorkLoop(0);
 594             inEvent->setNext(0);
 595             inEvent->release();
 596             SETP(&fFlags, kLoopRestart);
 597         }
 598         break;
 599
 600     default:
 601         return kIOReturnUnsupported;
 602     }
 603
 604     return res;
 605 }
 606
 607 bool
 608 IOWorkLoop::eventSourcePerformsWork(IOEventSource *inEventSource)
 609 {
 610         bool    result = true;
 611
 612         /*
 613          * The idea here is to see if the subclass of IOEventSource has overridden checkForWork().
 614          * The assumption is that if you override checkForWork(), you need to be
 615          * active and not passive.
 616          *
 617          * We picked a known quantity controlG that does not override
 618          * IOEventSource::checkForWork(), namely the IOCommandGate associated with
 619          * the workloop to which this event source is getting attached.
 620          *
 621          * We do a pointer comparison on the offset in the vtable for inNewEvent against
 622          * the offset in the vtable for inReferenceEvent. This works because
 623          * IOCommandGate's slot for checkForWork() has the address of
 624          * IOEventSource::checkForWork() in it.
 625          *
 626          * Think of OSMemberFunctionCast yielding the value at the vtable offset for
 627          * checkForWork() here. We're just testing to see if it's the same or not.
 628          *
 629          */
 630         if (controlG) {
 631                 void *  ptr1;
 632                 void *  ptr2;
 633
 634                 ptr1 = OSMemberFunctionCast(void*, inEventSource, &IOEventSource::checkForWork);
 635                 ptr2 = OSMemberFunctionCast(void*, controlG, &IOEventSource::checkForWork);
 636
 637                 if (ptr1 == ptr2)
 638                         result = false;
 639         }
 640
 641     return result;
 642 }