1 /* 2 * Copyright (c) 1998-2019 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 #ifndef __IOKIT_IOWORKLOOP_H 30 #define __IOKIT_IOWORKLOOP_H 31 32 #include <libkern/c++/OSObject.h> 33 #include <IOKit/IOReturn.h> 34 #include <IOKit/IOLib.h> 35 #include <IOKit/IOLocks.h> 36 #include <libkern/c++/OSPtr.h> 37 38 #include <IOKit/system.h> 39 40 #if IOKITSTATS 41 #include <IOKit/IOStatisticsPrivate.h> 42 #endif 43 44 class IOEventSource; 45 class IOTimerEventSource; 46 class IOCommandGate; 47 48 /*! @class IOWorkLoop 49 * @discussion An IOWorkLoop is a thread of control that is intended to be used to provide single threaded access to hardware. This class has no knowledge of the nature and type of the events that it marshals and forwards. When a device driver successfully starts (see IOService::start), it is expected to create the event sources it will need to receive events. Then a work loop is initialized and the events are added to the work loop for monitoring. In general this set up will be automated by the family superclass of the specific device. 50 * <br><br> 51 * The thread main method walks the event source linked list and messages each one requesting a work check. At this point each event source is expected to notify its registered owner that the event has occurred. After each event has been walked and each indicates that another loop isn't required (by setting the 'more' flag to false) the thread will go to sleep on a signaling semaphore. 52 * <br><br> 53 * When an event source is registered with a work loop it is informed of the semaphore to use to wake up the loop. 54 */ 55 class IOWorkLoop : public OSObject 56 { 57 OSDeclareDefaultStructors(IOWorkLoop); 58 59 public: 60 /*! 61 * @typedef Action 62 * @discussion Type and arguments of callout C function that is used when 63 * a runCommand is executed by a client. Cast to this type when you want a C++ 64 * member function to be used. Note the arg1 - arg3 parameters are straight pass 65 * through from the runCommand to the action callout. 66 * @param target 67 * Target of the function, can be used as a refcon. Note if a C++ function 68 * was specified, this parameter is implicitly the first parameter in the target 69 * member function's parameter list. 70 * @param arg0 Argument to action from run operation. 71 * @param arg1 Argument to action from run operation. 72 * @param arg2 Argument to action from run operation. 73 * @param arg3 Argument to action from run operation. 74 */ 75 typedef IOReturn (*Action)(OSObject *target, 76 void *arg0, void *arg1, 77 void *arg2, void *arg3); 78 79 #ifdef __BLOCKS__ 80 typedef IOReturn (^ActionBlock)(); 81 #endif /* __BLOCKS__ */ 82 83 enum { 84 kPreciousStack = 0x00000001, 85 kTimeLockPanics = 0x00000002, 86 }; 87 88 private: 89 /*! @function threadMainContinuation 90 * @abstract Static function that calls the threadMain function. 91 */ 92 static void threadMainContinuation(IOWorkLoop *self); 93 94 /*! @function eventSourcePerformsWork 95 * @abstract Checks if the event source passed in overrides checkForWork() to perform any work. 96 * IOWorkLoop uses this to determine if the event source should be polled in runEventSources() or not. 97 * @param inEventSource The event source to check. 98 */ 99 bool eventSourcePerformsWork(IOEventSource *inEventSource); 100 101 /*! @function releaseEventChain 102 * @abstract Static function that releases the events in a chain and sets 103 * their work loops to NULL. 104 */ 105 static void releaseEventChain(LIBKERN_CONSUMED IOEventSource *eventChain); 106 107 protected: 108 109 /*! @typedef maintCommandEnum 110 * @discussion Enumeration of commands that _maintCommand can deal with. 111 * @constant mAddEvent Used to tag a Remove event source command. 112 * @constant mRemoveEvent Used to tag a Remove event source command. 113 */ 114 typedef enum { mAddEvent, mRemoveEvent } maintCommandEnum; 115 116 /*! @var gateLock 117 * Mutual exclusion lock that is used by close and open Gate functions. 118 * This is a recursive lock, which allows multiple layers of code to share a single IOWorkLoop without deadlock. This is common in IOKit since threads of execution tend to follow the service plane in the IORegistry, and multiple objects along the call path may acquire the gate for the same (shared) workloop. 119 */ 120 IORecursiveLock *gateLock; 121 122 /*! @var eventChain 123 * Pointer to first event source in linked list. 124 */ 125 IOEventSource *eventChain; 126 127 /*! @var controlG 128 * Internal control gate to maintain event system. 129 */ 130 IOCommandGate *controlG; 131 132 /*! @var workToDoLock 133 * The spin lock that is used to guard the 'workToDo' variable. 134 */ 135 IOSimpleLock *workToDoLock; 136 137 /*! @var workThread 138 * Work loop thread. 139 */ 140 IOThread workThread; 141 142 /*! @var workToDo 143 * Used to to indicate that an interrupt has fired and needs to be processed. 144 */ 145 volatile bool workToDo; 146 147 /*! @var loopRestart 148 * Set if an event chain has been changed and the system has to be rechecked from start. (Internal use only) 149 */ 150 bool loopRestart; 151 152 /*! @struct ExpansionData 153 * @discussion This structure will be used to expand the capablilties of the IOWorkLoop in the future. 154 */ 155 struct ExpansionData { 156 IOOptionBits options; 157 IOEventSource *passiveEventChain; 158 #if IOKITSTATS 159 struct IOWorkLoopCounter *counter; 160 #else 161 void *iokitstatsReserved; 162 #endif 163 uint64_t lockInterval; 164 uint64_t lockTime; 165 }; 166 167 /*! @var reserved 168 * Reserved for future use. (Internal use only) 169 */ 170 ExpansionData *reserved; 171 172 /*! @function _maintRequest 173 * @abstract Synchronous implementation of addEventSource and removeEventSource functions. 174 * @discussion This function implements the commands as defined in the maintCommandEnum. It can be subclassed but it isn't an external API in the usual sense. A subclass implementation of _maintRequest would be called synchronously with respect to the work loop and it should be implemented in the usual way that an ioctl would be. 175 * @return kIOReturnUnsupported if the command given is not implemented, kIOReturnSuccess otherwise. 176 */ 177 virtual IOReturn _maintRequest(void *command, void *data, void *, void *); 178 179 /*! @function free 180 * @discussion Mandatory free of the object independent of the current retain count. If the work loop is running, this method will not return until the thread has successfully terminated. Each event source in the chain will be released and the working semaphore will be destroyed. 181 * <br><br> 182 * If the client has some outstanding requests on an event they will never be informed of completion. If an external thread is blocked on any of the event sources they will be awakened with a KERN_INTERUPTED status. 183 */ 184 virtual void free() APPLE_KEXT_OVERRIDE; 185 186 /*! @function threadMain 187 * @discussion Work loop threads main function. This function consists of 3 188 * loops: the outermost loop is the semaphore clear and wait loop, the middle 189 * loop terminates when there is no more work, and the inside loop walks the 190 * event list calling the checkForWork method in each event source. If an 191 * event source has more work to do, it can set the more flag and the middle 192 * loop will repeat. When no more work is outstanding the outermost will 193 * sleep until an event is signalled. 194 */ 195 virtual void threadMain(); 196 197 public: 198 199 /*! @function workLoop 200 * @abstract Factory member function to construct and intialize a work loop. 201 * @result Returns a workLoop instance if constructed successfully, 0 otherwise. 202 */ 203 static OSPtr<IOWorkLoop> workLoop(); 204 205 /*! @function workLoopWithOptions(IOOptionBits options) 206 * @abstract Factory member function to constuct and intialize a work loop. 207 * @param options Options - kPreciousStack to avoid stack deallocation on paging path. 208 * @result Returns a workLoop instance if constructed successfully, 0 otherwise. 209 */ 210 static OSPtr<IOWorkLoop> workLoopWithOptions(IOOptionBits options); 211 212 /*! @function init 213 * @discussion Initializes an instance of the workloop. This method creates and initializes the signaling semaphore, the controller gate lock, and spawns the thread that will continue executing. 214 * @result Returns true if initialized successfully, false otherwise. 215 */ 216 virtual bool init() APPLE_KEXT_OVERRIDE; 217 218 /*! @function getThread 219 * @abstract Gets the workThread. 220 * @result Returns workThread. 221 */ 222 virtual IOThread getThread() const; 223 224 /*! @function onThread 225 * @abstract Is the current execution context on the work thread? 226 * @result Returns true if IOThreadSelf() == workThread. 227 */ 228 virtual bool onThread() const; 229 230 /*! @function inGate 231 * @abstract Is the current execution context holding the work-loop's gate? 232 * @result Returns true if IOThreadSelf() is gate holder. 233 */ 234 virtual bool inGate() const; 235 236 /*! @function addEventSource 237 * @discussion Add an event source to be monitored by the work loop. This function does not return until the work loop has acknowledged the arrival of the new event source. When a new event has been added the threadMain will always restart its loop and check all outstanding events. The event source is retained by the work loop. 238 * @param newEvent Pointer to IOEventSource subclass to add. 239 * @result Always returns kIOReturnSuccess. 240 */ 241 virtual IOReturn addEventSource(IOEventSource *newEvent); 242 243 /*! @function removeEventSource 244 * @discussion Remove an event source from the work loop. This function does not return until the work loop has acknowledged the removal of the event source. When an event has been removed the threadMain will always restart its loop and check all outstanding events. The event source will be released before return. 245 * @param toRemove Pointer to IOEventSource subclass to remove. 246 * @result Returns kIOReturnSuccess if successful, kIOReturnBadArgument if toRemove couldn't be found. 247 */ 248 virtual IOReturn removeEventSource(IOEventSource *toRemove); 249 250 /*! @function enableAllEventSources 251 * @abstract Calls enable() in all event sources. 252 * @discussion For all event sources in eventChain, call enable() function. See IOEventSource::enable(). 253 */ 254 virtual void enableAllEventSources() const; 255 256 /*! @function disableAllEventSources 257 * @abstract Calls disable() in all event sources. 258 * @discussion For all event sources in eventChain, call disable() function. See IOEventSource::disable(). 259 */ 260 virtual void disableAllEventSources() const; 261 262 /*! @function enableAllInterrupts 263 * @abstract Calls enable() in all interrupt event sources. 264 * @discussion For all event sources (ES) for which OSDynamicCast(IOInterruptEventSource, ES) is valid, in eventChain call enable() function. See IOEventSource::enable(). 265 */ 266 virtual void enableAllInterrupts() const; 267 268 /*! @function disableAllInterrupts 269 * @abstract Calls disable() in all interrupt event sources. 270 * @discussion For all event sources (ES) for which OSDynamicCast(IOInterruptEventSource, ES) is valid, in eventChain call disable() function. See IOEventSource::disable(). 271 */ 272 virtual void disableAllInterrupts() const; 273 274 275 protected: 276 // Internal APIs used by event sources to control the thread 277 friend class IOEventSource; 278 friend class IOTimerEventSource; 279 friend class IOCommandGate; 280 #if IOKITSTATS 281 friend class IOStatistics; 282 #endif 283 virtual void signalWorkAvailable(); 284 virtual void openGate(); 285 virtual void closeGate(); 286 virtual bool tryCloseGate(); 287 virtual int sleepGate(void *event, UInt32 interuptibleType); 288 virtual void wakeupGate(void *event, bool oneThread); 289 290 public: 291 /* methods available in Mac OS X 10.1 or later */ 292 293 /*! @function runAction 294 * @abstract Single thread a call to an action with the work-loop. 295 * @discussion Client function that causes the given action to be called in a single threaded manner. Beware: the work-loop's gate is recursive and runAction can cause direct or indirect re-entrancy. When executing on a client's thread, runAction will sleep until the work-loop's gate opens for execution of client actions, the action is single threaded against all other work-loop event sources. 296 * @param action Pointer to function to be executed in work-loop context. 297 * @param arg0 Parameter for action parameter, defaults to 0. 298 * @param arg1 Parameter for action parameter, defaults to 0. 299 * @param arg2 Parameter for action parameter, defaults to 0. 300 * @param arg3 Parameter for action parameter, defaults to 0. 301 * @result Returns the value of the Action callout. 302 */ 303 virtual IOReturn runAction(Action action, OSObject *target, 304 void *arg0 = NULL, void *arg1 = NULL, 305 void *arg2 = NULL, void *arg3 = NULL); 306 307 #ifdef __BLOCKS__ 308 /*! @function runAction 309 * @abstract Single thread a call to an action with the work-loop. 310 * @discussion Client function that causes the given action to be called in a single threaded manner. Beware: the work-loop's gate is recursive and runAction can cause direct or indirect re-entrancy. When executing on a client's thread, runAction will sleep until the work-loop's gate opens for execution of client actions, the action is single threaded against all other work-loop event sources. 311 * @param action Block to be executed in work-loop context. 312 * @result Returns the result of the action block. 313 */ 314 IOReturn runActionBlock(ActionBlock action); 315 #endif /* __BLOCKS__ */ 316 317 /*! @function runEventSources 318 * @discussion Consists of the inner 2 loops of the threadMain function(qv). 319 * The outer loop terminates when there is no more work, and the inside loop 320 * walks the event list calling the checkForWork method in each event source. 321 * If an event source has more work to do, it can set the more flag and the 322 * outer loop will repeat. 323 * <br><br> 324 * This function can be used to clear a priority inversion between the normal 325 * workloop thread and multimedia's real time threads. The problem is that 326 * the interrupt action routine is often held off by high priority threads. 327 * So if they want to get their data now they will have to call us and ask if 328 * any data is available. The multi-media user client will arrange for this 329 * function to be called, which causes any pending interrupts to be processed 330 * and the completion routines called. By the time the function returns all 331 * outstanding work will have been completed at the real time threads 332 * priority. 333 * 334 * @result Return false if the work loop is shutting down, true otherwise. 335 */ 336 virtual bool runEventSources(); 337 338 /*! @function setMaximumLockTime 339 * @discussion For diagnostics use in DEVELOPMENT kernels, set a time interval which if the work loop lock is held for this time or greater, IOWorkLoop will panic or log a backtrace. 340 * @param interval An absolute time interval, eg. created with clock_interval_to_absolutetime_interval(). 341 * @param options Pass IOWorkLoop::kTimeLockPanics to panic when the time is exceeded, otherwise a log will be generated with OSReportWithBacktrace(). 342 */ 343 void setMaximumLockTime(uint64_t interval, uint32_t options); 344 345 protected: 346 // Internal APIs used by event sources to control the thread 347 virtual int sleepGate(void *event, AbsoluteTime deadline, UInt32 interuptibleType); 348 349 #if XNU_KERNEL_PRIVATE 350 void lockTime(void); 351 #endif /* XNU_KERNEL_PRIVATE */ 352 353 protected: 354 #if __LP64__ 355 OSMetaClassDeclareReservedUnused(IOWorkLoop, 0); 356 OSMetaClassDeclareReservedUnused(IOWorkLoop, 1); 357 OSMetaClassDeclareReservedUnused(IOWorkLoop, 2); 358 #else 359 OSMetaClassDeclareReservedUsedX86(IOWorkLoop, 0); 360 OSMetaClassDeclareReservedUsedX86(IOWorkLoop, 1); 361 OSMetaClassDeclareReservedUsedX86(IOWorkLoop, 2); 362 #endif 363 OSMetaClassDeclareReservedUnused(IOWorkLoop, 3); 364 OSMetaClassDeclareReservedUnused(IOWorkLoop, 4); 365 OSMetaClassDeclareReservedUnused(IOWorkLoop, 5); 366 OSMetaClassDeclareReservedUnused(IOWorkLoop, 6); 367 OSMetaClassDeclareReservedUnused(IOWorkLoop, 7); 368 }; 369 370 #endif /* !__IOKIT_IOWORKLOOP_H */ 371