iokit/IOKit/IOWorkLoop.h

   1 /*
   2  * Copyright (c) 1998-2007 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.
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  26  * @APPLE_OSREFERENCE_LICENSE_HEADER_END@
  27  */
  28 /*
  29 Copyright (c) 1998 Apple Computer, Inc.  All rights reserved.
  30 HISTORY
  31     1998-7-13   Godfrey van der Linden(gvdl)
  32         Created.
  33     1998-10-30  Godfrey van der Linden(gvdl)
  34         Converted to C++
  35 */
  36
  37 #ifndef __IOKIT_IOWORKLOOP_H
  38 #define __IOKIT_IOWORKLOOP_H
  39
  40 #include <libkern/c++/OSObject.h>
  41 #include <IOKit/IOReturn.h>
  42 #include <IOKit/IOLib.h>
  43 #include <IOKit/IOLocks.h>
  44
  45 #include <IOKit/system.h>
  46
  47 class IOEventSource;
  48 class IOTimerEventSource;
  49 class IOCommandGate;
  50
  51 /*! @class IOWorkLoop
  52     @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.
  53 <br><br>
  54         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.
  55 <br><br>
  56         When an event source is registered with a work loop it is informed of the semaphore to use to wake up the loop.
  57 */
  58 class IOWorkLoop : public OSObject
  59 {
  60     OSDeclareDefaultStructors(IOWorkLoop)
  61
  62 public:
  63 /*!
  64     @typedef Action
  65     @discussion Type and arguments of callout C function that is used when
  66 a runCommand is executed by a client.  Cast to this type when you want a C++
  67 member function to be used.  Note the arg1 - arg3 parameters are straight pass
  68 through from the runCommand to the action callout.
  69     @param target
  70         Target of the function, can be used as a refcon.  Note if a C++ function
  71 was specified, this parameter is implicitly the first parameter in the target
  72 member function's parameter list.
  73     @param arg0 Argument to action from run operation.
  74     @param arg1 Argument to action from run operation.
  75     @param arg2 Argument to action from run operation.
  76     @param arg3 Argument to action from run operation.
  77 */
  78     typedef IOReturn (*Action)(OSObject *target,
  79                                void *arg0, void *arg1,
  80                                void *arg2, void *arg3);
  81     enum {
  82         kPreciousStack = 0x00000001
  83     };
  84
  85 private:
  86 /*! @function threadMainContinuation
  87     @abstract Static function that calls the threadMain function.
  88 */
  89     static void threadMainContinuation(IOWorkLoop *self);
  90
  91 protected:
  92
  93 /*! @typedef maintCommandEnum
  94     @discussion Enumeration of commands that _maintCommand can deal with.
  95     @constant mAddEvent Used to tag a Remove event source command.
  96     @constant mRemoveEvent Used to tag a Remove event source command.
  97 */
  98     typedef enum { mAddEvent, mRemoveEvent } maintCommandEnum;
  99
 100 /*! @var gateLock
 101     Mutual exclusion lock that is used by close and open Gate functions.
 102     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.
 103 */
 104     IORecursiveLock *gateLock;
 105
 106 /*! @var eventChain
 107     Pointer to first event source in linked list.
 108 */
 109     IOEventSource *eventChain;
 110
 111 /*! @var controlG
 112     Internal control gate to maintain event system.
 113 */
 114     IOCommandGate *controlG;
 115
 116 /*! @var workToDoLock
 117     The spin lock that is used to guard the 'workToDo' variable.
 118 */
 119     IOSimpleLock *workToDoLock;
 120
 121 /*! @var workThread
 122     Work loop thread.
 123 */
 124     IOThread workThread;
 125
 126 /*! @var workToDo
 127     Used to to indicate that an interrupt has fired and needs to be processed.
 128 */
 129     volatile bool workToDo;
 130
 131 /*! @var loopRestart
 132     Set if an event chain has been changed and the system has to be rechecked from start.  (Internal use only)
 133 */
 134     bool loopRestart;
 135
 136 /*! @struct ExpansionData
 137     @discussion This structure will be used to expand the capablilties of the IOWorkLoop in the future.
 138 */
 139     struct ExpansionData {
 140         IOOptionBits options;
 141     };
 142
 143 /*! @var reserved
 144     Reserved for future use.  (Internal use only)
 145 */
 146     ExpansionData *reserved;
 147
 148 /*! @function _maintRequest
 149     @abstract Synchronous implementation of addEventSource and removeEventSource functions.
 150     @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.
 151     @return kIOReturnUnsupported if the command given is not implemented, kIOReturnSuccess otherwise.
 152 */
 153     virtual IOReturn _maintRequest(void *command, void *data, void *, void *);
 154
 155 /*! @function free
 156     @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.
 157 <br><br>
 158         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.
 159 */
 160     virtual void free();
 161
 162 /*! @function threadMain
 163     @discussion Work loop threads main function.  This function consists of 3
 164     loops: the outermost loop is the semaphore clear and wait loop, the middle
 165     loop terminates when there is no more work, and the inside loop walks the
 166     event list calling the checkForWork method in each event source.  If an
 167     event source has more work to do, it can set the more flag and the middle
 168     loop will repeat.  When no more work is outstanding the outermost will
 169     sleep until an event is signalled.
 170 */
 171     virtual void threadMain();
 172
 173 public:
 174
 175 /*! @function workLoop
 176     @abstract Factory member function to construct and intialize a work loop.
 177     @result Returns a workLoop instance if constructed successfully, 0 otherwise.
 178 */
 179     static IOWorkLoop *workLoop();
 180
 181 /*! @function workLoopWithOptions(IOOptionBits options)
 182     @abstract Factory member function to constuct and intialize a work loop.
 183     @param options Options - kPreciousStack to avoid stack deallocation on paging path.
 184     @result Returns a workLoop instance if constructed successfully, 0 otherwise.
 185 */
 186     static IOWorkLoop *workLoopWithOptions(IOOptionBits options);
 187
 188 /*! @function init
 189     @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.
 190     @result Returns true if initialized successfully, false otherwise.
 191 */
 192     virtual bool init();
 193
 194 /*! @function getThread
 195     @abstract Gets the workThread.
 196     @result Returns workThread.
 197 */
 198     virtual IOThread getThread() const;
 199
 200 /*! @function onThread
 201     @abstract Is the current execution context on the work thread?
 202     @result Returns true if IOThreadSelf() == workThread.
 203 */
 204     virtual bool onThread() const;
 205
 206 /*! @function inGate
 207     @abstract Is the current execution context holding the work-loop's gate?
 208     @result Returns true if IOThreadSelf() is gate holder.
 209 */
 210     virtual bool inGate() const;
 211
 212 /*! @function addEventSource
 213     @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.
 214     @param newEvent Pointer to IOEventSource subclass to add.
 215     @result Always returns kIOReturnSuccess.
 216 */
 217     virtual IOReturn addEventSource(IOEventSource *newEvent);
 218
 219 /*! @function removeEventSource
 220     @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.
 221     @param toRemove Pointer to IOEventSource subclass to remove.
 222     @result Returns kIOReturnSuccess if successful, kIOReturnBadArgument if toRemove couldn't be found.
 223 */
 224     virtual IOReturn removeEventSource(IOEventSource *toRemove);
 225
 226 /*! @function enableAllEventSources
 227     @abstract Calls enable() in all event sources.
 228     @discussion For all event sources in eventChain, call enable() function.  See IOEventSource::enable().
 229 */
 230     virtual void enableAllEventSources() const;
 231
 232 /*! @function disableAllEventSources
 233     @abstract Calls disable() in all event sources.
 234     @discussion For all event sources in eventChain, call disable() function.  See IOEventSource::disable().
 235 */
 236     virtual void disableAllEventSources() const;
 237
 238 /*! @function enableAllInterrupts
 239     @abstract Calls enable() in all interrupt event sources.
 240     @discussion For all event sources (ES) for which IODynamicCast(IOInterruptEventSource, ES) is valid, in eventChain call enable() function.  See IOEventSource::enable().
 241 */
 242     virtual void enableAllInterrupts() const;
 243
 244 /*! @function disableAllInterrupts
 245     @abstract Calls disable() in all interrupt event sources.
 246     @discussion For all event sources (ES) for which IODynamicCast(IOInterruptEventSource, ES) is valid,  in eventChain call disable() function.  See IOEventSource::disable().
 247 */
 248     virtual void disableAllInterrupts() const;
 249
 250
 251 protected:
 252     // Internal APIs used by event sources to control the thread
 253     friend class IOEventSource;
 254     friend class IOTimerEventSource;
 255     virtual void signalWorkAvailable();
 256     virtual void openGate();
 257     virtual void closeGate();
 258     virtual bool tryCloseGate();
 259     virtual int  sleepGate(void *event, UInt32 interuptibleType);
 260     virtual void wakeupGate(void *event, bool oneThread);
 261
 262 public:
 263     /* methods available in Mac OS X 10.1 or later */
 264
 265 /*! @function runAction
 266     @abstract Single thread a call to an action with the work-loop.
 267     @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.
 268     @param action Pointer to function to be executed in work-loop context.
 269     @param arg0 Parameter for action parameter, defaults to 0.
 270     @param arg1 Parameter for action parameter, defaults to 0.
 271     @param arg2 Parameter for action parameter, defaults to 0.
 272     @param arg3 Parameter for action parameter, defaults to 0.
 273     @result Returns the value of the Action callout.
 274 */
 275     OSMetaClassDeclareReservedUsed(IOWorkLoop, 0);
 276     virtual IOReturn runAction(Action action, OSObject *target,
 277                                void *arg0 = 0, void *arg1 = 0,
 278                                void *arg2 = 0, void *arg3 = 0);
 279
 280 /*! @function runEventSources
 281     @discussion Consists of the inner 2 loops of the threadMain function(qv).
 282     The outer loop terminates when there is no more work, and the inside loop
 283     walks the event list calling the checkForWork method in each event source.
 284     If an event source has more work to do, it can set the more flag and the
 285     outer loop will repeat.
 286 <br><br>
 287     This function can be used to clear a priority inversion between the normal
 288     workloop thread and multimedia's real time threads.  The problem is that
 289     the interrupt action routine is often held off by high priority threads.
 290     So if they want to get their data now they will have to call us and ask if
 291     any data is available.  The multi-media user client will arrange for this
 292     function to be called, which causes any pending interrupts to be processed
 293     and the completion routines called.  By the time the function returns all
 294     outstanding work will have been completed at the real time threads
 295     priority.
 296
 297     @result Return false if the work loop is shutting down, true otherwise.
 298 */
 299     OSMetaClassDeclareReservedUsed(IOWorkLoop, 1);
 300     virtual bool runEventSources();
 301
 302 protected:
 303
 304     OSMetaClassDeclareReservedUnused(IOWorkLoop, 2);
 305     OSMetaClassDeclareReservedUnused(IOWorkLoop, 3);
 306     OSMetaClassDeclareReservedUnused(IOWorkLoop, 4);
 307     OSMetaClassDeclareReservedUnused(IOWorkLoop, 5);
 308     OSMetaClassDeclareReservedUnused(IOWorkLoop, 6);
 309     OSMetaClassDeclareReservedUnused(IOWorkLoop, 7);
 310 };
 311
 312 #endif /* !__IOKIT_IOWORKLOOP_H */