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
  37 #include <IOKit/system.h>
  38
  39 #if IOKITSTATS
  40 #include <IOKit/IOStatisticsPrivate.h>
  41 #endif
  42
  43 class IOEventSource;
  44 class IOTimerEventSource;
  45 class IOCommandGate;
  46
  47 /*! @class IOWorkLoop
  48     @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.
  49 <br><br>
  50         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.
  51 <br><br>
  52         When an event source is registered with a work loop it is informed of the semaphore to use to wake up the loop.
  53 */
  54 class IOWorkLoop : public OSObject
  55 {
  56     OSDeclareDefaultStructors(IOWorkLoop)
  57
  58 public:
  59 /*!
  60     @typedef Action
  61     @discussion Type and arguments of callout C function that is used when
  62 a runCommand is executed by a client.  Cast to this type when you want a C++
  63 member function to be used.  Note the arg1 - arg3 parameters are straight pass
  64 through from the runCommand to the action callout.
  65     @param target
  66         Target of the function, can be used as a refcon.  Note if a C++ function
  67 was specified, this parameter is implicitly the first parameter in the target
  68 member function's parameter list.
  69     @param arg0 Argument to action from run operation.
  70     @param arg1 Argument to action from run operation.
  71     @param arg2 Argument to action from run operation.
  72     @param arg3 Argument to action from run operation.
  73 */
  74     typedef IOReturn (*Action)(OSObject *target,
  75                                void *arg0, void *arg1,
  76                                void *arg2, void *arg3);
  77     enum {
  78         kPreciousStack = 0x00000001
  79     };
  80
  81 private:
  82 /*! @function threadMainContinuation
  83     @abstract Static function that calls the threadMain function.
  84 */
  85     static void threadMainContinuation(IOWorkLoop *self);
  86
  87 /*! @function eventSourcePerformsWork
  88         @abstract Checks if the event source passed in overrides checkForWork() to perform any work.
  89 IOWorkLoop uses this to determine if the event source should be polled in runEventSources() or not.
  90         @param inEventSource The event source to check.
  91 */
  92         bool eventSourcePerformsWork(IOEventSource *inEventSource);
  93
  94 protected:
  95
  96 /*! @typedef maintCommandEnum
  97     @discussion Enumeration of commands that _maintCommand can deal with.
  98     @constant mAddEvent Used to tag a Remove event source command.
  99     @constant mRemoveEvent Used to tag a Remove event source command.
 100 */
 101     typedef enum { mAddEvent, mRemoveEvent } maintCommandEnum;
 102
 103 /*! @var gateLock
 104     Mutual exclusion lock that is used by close and open Gate functions.
 105     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.
 106 */
 107     IORecursiveLock *gateLock;
 108
 109 /*! @var eventChain
 110     Pointer to first event source in linked list.
 111 */
 112     IOEventSource *eventChain;
 113
 114 /*! @var controlG
 115     Internal control gate to maintain event system.
 116 */
 117     IOCommandGate *controlG;
 118
 119 /*! @var workToDoLock
 120     The spin lock that is used to guard the 'workToDo' variable.
 121 */
 122     IOSimpleLock *workToDoLock;
 123
 124 /*! @var workThread
 125     Work loop thread.
 126 */
 127     IOThread workThread;
 128
 129 /*! @var workToDo
 130     Used to to indicate that an interrupt has fired and needs to be processed.
 131 */
 132     volatile bool workToDo;
 133
 134 /*! @var loopRestart
 135     Set if an event chain has been changed and the system has to be rechecked from start.  (Internal use only)
 136 */
 137     bool loopRestart;
 138
 139 /*! @struct ExpansionData
 140     @discussion This structure will be used to expand the capablilties of the IOWorkLoop in the future.
 141 */
 142     struct ExpansionData {
 143         IOOptionBits options;
 144         IOEventSource *passiveEventChain;
 145 #if DEBUG
 146         void * allocationBacktrace[16];
 147 #endif /* DEBUG */
 148 #if IOKITSTATS
 149         struct IOWorkLoopCounter *counter;
 150 #else
 151         void *iokitstatsReserved;
 152 #endif
 153     };
 154
 155 /*! @var reserved
 156     Reserved for future use.  (Internal use only)
 157 */
 158     ExpansionData *reserved;
 159
 160 /*! @function _maintRequest
 161     @abstract Synchronous implementation of addEventSource and removeEventSource functions.
 162     @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.
 163     @return kIOReturnUnsupported if the command given is not implemented, kIOReturnSuccess otherwise.
 164 */
 165     virtual IOReturn _maintRequest(void *command, void *data, void *, void *);
 166
 167 /*! @function free
 168     @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.
 169 <br><br>
 170         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.
 171 */
 172     virtual void free();
 173
 174 /*! @function threadMain
 175     @discussion Work loop threads main function.  This function consists of 3
 176     loops: the outermost loop is the semaphore clear and wait loop, the middle
 177     loop terminates when there is no more work, and the inside loop walks the
 178     event list calling the checkForWork method in each event source.  If an
 179     event source has more work to do, it can set the more flag and the middle
 180     loop will repeat.  When no more work is outstanding the outermost will
 181     sleep until an event is signalled.
 182 */
 183     virtual void threadMain();
 184
 185 public:
 186
 187 /*! @function workLoop
 188     @abstract Factory member function to construct and intialize a work loop.
 189     @result Returns a workLoop instance if constructed successfully, 0 otherwise.
 190 */
 191     static IOWorkLoop *workLoop();
 192
 193 /*! @function workLoopWithOptions(IOOptionBits options)
 194     @abstract Factory member function to constuct and intialize a work loop.
 195     @param options Options - kPreciousStack to avoid stack deallocation on paging path.
 196     @result Returns a workLoop instance if constructed successfully, 0 otherwise.
 197 */
 198     static IOWorkLoop *workLoopWithOptions(IOOptionBits options);
 199
 200 /*! @function init
 201     @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.
 202     @result Returns true if initialized successfully, false otherwise.
 203 */
 204     virtual bool init();
 205
 206 /*! @function getThread
 207     @abstract Gets the workThread.
 208     @result Returns workThread.
 209 */
 210     virtual IOThread getThread() const;
 211
 212 /*! @function onThread
 213     @abstract Is the current execution context on the work thread?
 214     @result Returns true if IOThreadSelf() == workThread.
 215 */
 216     virtual bool onThread() const;
 217
 218 /*! @function inGate
 219     @abstract Is the current execution context holding the work-loop's gate?
 220     @result Returns true if IOThreadSelf() is gate holder.
 221 */
 222     virtual bool inGate() const;
 223
 224 /*! @function addEventSource
 225     @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.
 226     @param newEvent Pointer to IOEventSource subclass to add.
 227     @result Always returns kIOReturnSuccess.
 228 */
 229     virtual IOReturn addEventSource(IOEventSource *newEvent);
 230
 231 /*! @function removeEventSource
 232     @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.
 233     @param toRemove Pointer to IOEventSource subclass to remove.
 234     @result Returns kIOReturnSuccess if successful, kIOReturnBadArgument if toRemove couldn't be found.
 235 */
 236     virtual IOReturn removeEventSource(IOEventSource *toRemove);
 237
 238 /*! @function enableAllEventSources
 239     @abstract Calls enable() in all event sources.
 240     @discussion For all event sources in eventChain, call enable() function.  See IOEventSource::enable().
 241 */
 242     virtual void enableAllEventSources() const;
 243
 244 /*! @function disableAllEventSources
 245     @abstract Calls disable() in all event sources.
 246     @discussion For all event sources in eventChain, call disable() function.  See IOEventSource::disable().
 247 */
 248     virtual void disableAllEventSources() const;
 249
 250 /*! @function enableAllInterrupts
 251     @abstract Calls enable() in all interrupt event sources.
 252     @discussion For all event sources (ES) for which OSDynamicCast(IOInterruptEventSource, ES) is valid, in eventChain call enable() function.  See IOEventSource::enable().
 253 */
 254     virtual void enableAllInterrupts() const;
 255
 256 /*! @function disableAllInterrupts
 257     @abstract Calls disable() in all interrupt event sources.
 258     @discussion For all event sources (ES) for which OSDynamicCast(IOInterruptEventSource, ES) is valid,  in eventChain call disable() function.  See IOEventSource::disable().
 259 */
 260     virtual void disableAllInterrupts() const;
 261
 262
 263 protected:
 264     // Internal APIs used by event sources to control the thread
 265     friend class IOEventSource;
 266     friend class IOTimerEventSource;
 267 #if IOKITSTATS
 268     friend class IOStatistics;
 269 #endif
 270     virtual void signalWorkAvailable();
 271     virtual void openGate();
 272     virtual void closeGate();
 273     virtual bool tryCloseGate();
 274     virtual int  sleepGate(void *event, UInt32 interuptibleType);
 275     virtual void wakeupGate(void *event, bool oneThread);
 276
 277 public:
 278     /* methods available in Mac OS X 10.1 or later */
 279
 280 /*! @function runAction
 281     @abstract Single thread a call to an action with the work-loop.
 282     @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.
 283     @param action Pointer to function to be executed in work-loop context.
 284     @param arg0 Parameter for action parameter, defaults to 0.
 285     @param arg1 Parameter for action parameter, defaults to 0.
 286     @param arg2 Parameter for action parameter, defaults to 0.
 287     @param arg3 Parameter for action parameter, defaults to 0.
 288     @result Returns the value of the Action callout.
 289 */
 290     virtual IOReturn runAction(Action action, OSObject *target,
 291                                void *arg0 = 0, void *arg1 = 0,
 292                                void *arg2 = 0, void *arg3 = 0);
 293
 294 /*! @function runEventSources
 295     @discussion Consists of the inner 2 loops of the threadMain function(qv).
 296     The outer loop terminates when there is no more work, and the inside loop
 297     walks the event list calling the checkForWork method in each event source.
 298     If an event source has more work to do, it can set the more flag and the
 299     outer loop will repeat.
 300 <br><br>
 301     This function can be used to clear a priority inversion between the normal
 302     workloop thread and multimedia's real time threads.  The problem is that
 303     the interrupt action routine is often held off by high priority threads.
 304     So if they want to get their data now they will have to call us and ask if
 305     any data is available.  The multi-media user client will arrange for this
 306     function to be called, which causes any pending interrupts to be processed
 307     and the completion routines called.  By the time the function returns all
 308     outstanding work will have been completed at the real time threads
 309     priority.
 310
 311     @result Return false if the work loop is shutting down, true otherwise.
 312 */
 313     virtual bool runEventSources();
 314
 315 protected:
 316     // Internal APIs used by event sources to control the thread
 317     virtual int sleepGate(void *event, AbsoluteTime deadline, UInt32 interuptibleType);
 318
 319 protected:
 320 #if __LP64__
 321     OSMetaClassDeclareReservedUnused(IOWorkLoop, 0);
 322     OSMetaClassDeclareReservedUnused(IOWorkLoop, 1);
 323     OSMetaClassDeclareReservedUnused(IOWorkLoop, 2);
 324 #else
 325     OSMetaClassDeclareReservedUsed(IOWorkLoop, 0);
 326     OSMetaClassDeclareReservedUsed(IOWorkLoop, 1);
 327     OSMetaClassDeclareReservedUsed(IOWorkLoop, 2);
 328 #endif
 329     OSMetaClassDeclareReservedUnused(IOWorkLoop, 3);
 330     OSMetaClassDeclareReservedUnused(IOWorkLoop, 4);
 331     OSMetaClassDeclareReservedUnused(IOWorkLoop, 5);
 332     OSMetaClassDeclareReservedUnused(IOWorkLoop, 6);
 333     OSMetaClassDeclareReservedUnused(IOWorkLoop, 7);
 334 };
 335
 336 #endif /* !__IOKIT_IOWORKLOOP_H */