iokit/IOKit/IOWorkLoop.h

   1 /*
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  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 */