iokit/IOKit/IOLocks.h

   1 /*
   2  * Copyright (c) 1998-2012 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  *
  30  */
  31
  32 #ifndef __IOKIT_IOLOCKS_H
  33 #define __IOKIT_IOLOCKS_H
  34
  35 #ifndef KERNEL
  36 #error IOLocks.h is for kernel use only
  37 #endif
  38
  39 #include <sys/appleapiopts.h>
  40 #include <sys/cdefs.h>
  41
  42 #include <IOKit/system.h>
  43
  44 #include <IOKit/IOReturn.h>
  45 #include <IOKit/IOTypes.h>
  46
  47 #ifdef __cplusplus
  48 extern "C" {
  49 #endif
  50
  51 #include <libkern/locks.h>
  52 #include <machine/machine_routines.h>
  53
  54 /*! @var IOLockGroup
  55  *   Global lock group used by all IOKit locks.  To simplify kext debugging and lock-heat analysis, consider using lck_* locks with a per-driver lock group, as defined in kern/locks.h.
  56  */
  57 extern lck_grp_t        *IOLockGroup;
  58
  59 #if defined(XNU_KERNEL_PRIVATE)
  60 #define IOLOCKS_INLINE  1
  61 #endif
  62
  63 /*
  64  * Mutex lock operations
  65  */
  66
  67 #ifdef  IOLOCKS_INLINE
  68 typedef lck_mtx_t       IOLock;
  69 #else
  70 typedef struct _IOLock  IOLock;
  71 #endif  /* IOLOCKS_INLINE */
  72
  73
  74 /*! @function IOLockAlloc
  75  *   @abstract Allocates and initializes a mutex.
  76  *   @discussion Allocates a mutex in general purpose memory, and initializes it. Mutexes are general purpose blocking mutual exclusion locks, supplied by libkern/locks.h. This function may block and so should not be called from interrupt level or while a spin lock is held.  IOLocks use the global IOKit lock group, IOLockGroup.  To simplify kext debugging and lock-heat analysis, consider using lck_* locks with a per-driver lock group, as defined in kern/locks.h.
  77  *   @result Pointer to the allocated lock, or zero on failure. */
  78
  79 IOLock * IOLockAlloc( void );
  80
  81 /*! @function IOLockFree
  82  *   @abstract Frees a mutex.
  83  *   @discussion Frees a lock allocated with IOLockAlloc. Mutex should be unlocked with no waiters.
  84  *   @param lock Pointer to the allocated lock. */
  85
  86 void    IOLockFree( IOLock * lock);
  87
  88 /*! @function IOLockGetMachLock
  89  *   @abstract Accessor to a Mach mutex.
  90  *   @discussion Accessor to the Mach mutex.
  91  *   @param lock Pointer to the allocated lock. */
  92
  93 lck_mtx_t * IOLockGetMachLock( IOLock * lock);
  94
  95 /*! @function IOLockLock
  96  *   @abstract Lock a mutex.
  97  *   @discussion Lock the mutex. If the lock is held by any thread, block waiting for its unlock. This function may block and so should not be called from interrupt level or while a spin lock is held. Locking the mutex recursively from one thread will result in deadlock.
  98  *   @param lock Pointer to the allocated lock. */
  99
 100 #ifdef  IOLOCKS_INLINE
 101 #define IOLockLock(l)   lck_mtx_lock(l)
 102 #else
 103 void    IOLockLock( IOLock * lock);
 104 #endif  /* !IOLOCKS_INLINE */
 105
 106 /*! @function IOLockTryLock
 107  *   @abstract Attempt to lock a mutex.
 108  *   @discussion Lock the mutex if it is currently unlocked, and return true. If the lock is held by any thread, return false.
 109  *   @param lock Pointer to the allocated lock.
 110  *   @result True if the mutex was unlocked and is now locked by the caller, otherwise false. */
 111
 112 #ifdef  IOLOCKS_INLINE
 113 #define IOLockTryLock(l)        lck_mtx_try_lock(l)
 114 #else
 115 boolean_t IOLockTryLock( IOLock * lock);
 116 #endif  /* !IOLOCKS_INLINE */
 117
 118 /*! @function IOLockUnlock
 119  *   @abstract Unlock a mutex.
 120  *  @discussion Unlock the mutex and wake any blocked waiters. Results are undefined if the caller has not locked the mutex. This function may block and so should not be called from interrupt level or while a spin lock is held.
 121  *   @param lock Pointer to the allocated lock. */
 122
 123 #ifdef  IOLOCKS_INLINE
 124 #define IOLockUnlock(l) lck_mtx_unlock(l)
 125 #else
 126 void    IOLockUnlock( IOLock * lock);
 127 #endif  /* !IOLOCKS_INLINE */
 128
 129 /*! @function IOLockSleep
 130  *   @abstract Sleep with mutex unlock and relock
 131  *  @discussion Prepare to sleep,unlock the mutex, and re-acquire it on wakeup. Results are undefined if the caller has not locked the mutex. This function may block and so should not be called from interrupt level or while a spin lock is held.
 132  *   @param lock Pointer to the locked lock.
 133  *   @param event The event to sleep on. Must be non-NULL.
 134  *   @param interType How can the sleep be interrupted.
 135  *       @result The wait-result value indicating how the thread was awakened.*/
 136 int     IOLockSleep( IOLock * lock, void *event, UInt32 interType) __DARWIN14_ALIAS(IOLockSleep);
 137
 138 int     IOLockSleepDeadline( IOLock * lock, void *event,
 139     AbsoluteTime deadline, UInt32 interType) __DARWIN14_ALIAS(IOLockSleepDeadline);
 140
 141 void    IOLockWakeup(IOLock * lock, void *event, bool oneThread) __DARWIN14_ALIAS(IOLockWakeup);
 142
 143 #ifdef XNU_KERNEL_PRIVATE
 144 /*! @enum     IOLockAssertState
 145  *  @abstract Used with IOLockAssert to assert the state of a lock.
 146  */
 147 typedef enum {
 148         kIOLockAssertOwned    = LCK_ASSERT_OWNED,
 149         kIOLockAssertNotOwned = LCK_ASSERT_NOTOWNED
 150 } IOLockAssertState;
 151
 152 #ifdef IOLOCKS_INLINE
 153 #define IOLockAssert(l, type) LCK_MTX_ASSERT(l, type)
 154 #else
 155 /*! @function   IOLockAssert
 156  *  @abstract   Assert that lock is either held or not held by current thread.
 157  *  @discussion Call with either kIOLockAssertOwned or kIOLockAssertNotOwned.
 158  *  Panics the kernel if the lock is not owned if called with kIOLockAssertOwned,
 159  *  and vice-versa.
 160  */
 161 void    IOLockAssert(IOLock * lock, IOLockAssertState type);
 162 #endif /* !IOLOCKS_INLINE */
 163 #endif /* !XNU_KERNEL_PRIVATE */
 164
 165 #ifdef __APPLE_API_OBSOLETE
 166
 167 /* The following API is deprecated */
 168
 169 typedef enum {
 170         kIOLockStateUnlocked        = 0,
 171         kIOLockStateLocked          = 1
 172 } IOLockState;
 173
 174 void    IOLockInitWithState( IOLock * lock, IOLockState state);
 175 #define IOLockInit( l ) IOLockInitWithState( l, kIOLockStateUnlocked);
 176
 177 static __inline__ void
 178 IOTakeLock( IOLock * lock)
 179 {
 180         IOLockLock(lock);
 181 }
 182 static __inline__ boolean_t
 183 IOTryLock(  IOLock * lock)
 184 {
 185         return IOLockTryLock(lock);
 186 }
 187 static __inline__ void
 188 IOUnlock(   IOLock * lock)
 189 {
 190         IOLockUnlock(lock);
 191 }
 192
 193 #endif /* __APPLE_API_OBSOLETE */
 194
 195 /*
 196  * Recursive lock operations
 197  */
 198
 199 typedef struct _IORecursiveLock IORecursiveLock;
 200
 201 /*! @function IORecursiveLockAlloc
 202  *   @abstract Allocates and initializes an recursive lock.
 203  *   @discussion Allocates a recursive lock in general purpose memory, and initializes it. Recursive locks function identically to mutexes but allow one thread to lock more than once, with balanced unlocks.  IORecursiveLocks use the global IOKit lock group, IOLockGroup.  To simplify kext debugging and lock-heat analysis, consider using lck_* locks with a per-driver lock group, as defined in kern/locks.h.
 204  *   @result Pointer to the allocated lock, or zero on failure. */
 205
 206 IORecursiveLock * IORecursiveLockAlloc( void );
 207
 208 /*! @function IORecursiveLockFree
 209  *   @abstract Frees a recursive lock.
 210  *   @discussion Frees a lock allocated with IORecursiveLockAlloc. Lock should be unlocked with no waiters.
 211  *   @param lock Pointer to the allocated lock. */
 212
 213 void            IORecursiveLockFree( IORecursiveLock * lock);
 214
 215 /*! @function IORecursiveLockGetMachLock
 216  *   @abstract Accessor to a Mach mutex.
 217  *   @discussion Accessor to the Mach mutex.
 218  *   @param lock Pointer to the allocated lock. */
 219
 220 lck_mtx_t * IORecursiveLockGetMachLock( IORecursiveLock * lock);
 221
 222 /*! @function IORecursiveLockLock
 223  *   @abstract Lock a recursive lock.
 224  *   @discussion Lock the recursive lock. If the lock is held by another thread, block waiting for its unlock. This function may block and so should not be called from interrupt level or while a spin lock is held. The lock may be taken recursively by the same thread, with a balanced number of calls to IORecursiveLockUnlock.
 225  *   @param lock Pointer to the allocated lock. */
 226
 227 void            IORecursiveLockLock( IORecursiveLock * lock);
 228
 229 /*! @function IORecursiveLockTryLock
 230  *   @abstract Attempt to lock a recursive lock.
 231  *   @discussion Lock the lock if it is currently unlocked, or held by the calling thread, and return true. If the lock is held by another thread, return false. Successful calls to IORecursiveLockTryLock should be balanced with calls to IORecursiveLockUnlock.
 232  *   @param lock Pointer to the allocated lock.
 233  *   @result True if the lock is now locked by the caller, otherwise false. */
 234
 235 boolean_t       IORecursiveLockTryLock( IORecursiveLock * lock);
 236
 237 /*! @function IORecursiveLockUnlock
 238  *   @abstract Unlock a recursive lock.
 239  *  @discussion Undo one call to IORecursiveLockLock, if the lock is now unlocked wake any blocked waiters. Results are undefined if the caller does not balance calls to IORecursiveLockLock with IORecursiveLockUnlock. This function may block and so should not be called from interrupt level or while a spin lock is held.
 240  *   @param lock Pointer to the allocated lock. */
 241
 242 void            IORecursiveLockUnlock( IORecursiveLock * lock);
 243
 244 /*! @function IORecursiveLockHaveLock
 245  *   @abstract Check if a recursive lock is held by the calling thread.
 246  *   @discussion If the lock is held by the calling thread, return true, otherwise the lock is unlocked, or held by another thread and false is returned.
 247  *   @param lock Pointer to the allocated lock.
 248  *   @result True if the calling thread holds the lock otherwise false. */
 249
 250 boolean_t       IORecursiveLockHaveLock( const IORecursiveLock * lock);
 251
 252 extern int      IORecursiveLockSleep( IORecursiveLock *_lock,
 253     void *event, UInt32 interType);
 254 extern int      IORecursiveLockSleepDeadline( IORecursiveLock * _lock, void *event,
 255     AbsoluteTime deadline, UInt32 interType);
 256 extern void     IORecursiveLockWakeup( IORecursiveLock *_lock,
 257     void *event, bool oneThread);
 258
 259 /*
 260  * Complex (read/write) lock operations
 261  */
 262
 263 #ifdef  IOLOCKS_INLINE
 264 typedef lck_rw_t                IORWLock;
 265 #else
 266 typedef struct _IORWLock        IORWLock;
 267 #endif  /* IOLOCKS_INLINE */
 268
 269 /*! @function IORWLockAlloc
 270  *   @abstract Allocates and initializes a read/write lock.
 271  *   @discussion Allocates and initializes a read/write lock in general purpose memory. Read/write locks provide for multiple readers, one exclusive writer, and are supplied by libkern/locks.h. This function may block and so should not be called from interrupt level or while a spin lock is held.  IORWLocks use the global IOKit lock group, IOLockGroup.  To simplify kext debugging and lock-heat analysis, consider using lck_* locks with a per-driver lock group, as defined in kern/locks.h.
 272  *   @result Pointer to the allocated lock, or zero on failure. */
 273
 274 IORWLock * IORWLockAlloc( void );
 275
 276 /*! @function IORWLockFree
 277  *  @abstract Frees a read/write lock.
 278  *  @discussion Frees a lock allocated with IORWLockAlloc. Lock should be unlocked with no waiters.
 279  *   @param lock Pointer to the allocated lock. */
 280
 281 void    IORWLockFree( IORWLock * lock);
 282
 283 /*! @function IORWLockGetMachLock
 284  *   @abstract Accessor to a Mach read/write lock.
 285  *   @discussion Accessor to the Mach read/write lock.
 286  *   @param lock Pointer to the allocated lock. */
 287
 288 lck_rw_t * IORWLockGetMachLock( IORWLock * lock);
 289
 290 /*! @function IORWLockRead
 291  *   @abstract Lock a read/write lock for read.
 292  *  @discussion Lock the lock for read, allowing multiple readers when there are no writers. If the lock is held for write, block waiting for its unlock. This function may block and so should not be called from interrupt level or while a spin lock is held. Locking the lock recursively from one thread, for read or write, can result in deadlock.
 293  *   @param lock Pointer to the allocated lock. */
 294
 295 #ifdef  IOLOCKS_INLINE
 296 #define IORWLockRead(l) lck_rw_lock_shared(l)
 297 #else
 298 void    IORWLockRead(IORWLock * lock);
 299 #endif  /* !IOLOCKS_INLINE */
 300
 301 /*! @function IORWLockWrite
 302  *   @abstract Lock a read/write lock for write.
 303  *   @discussion Lock the lock for write, allowing one writer exlusive access. If the lock is held for read or write, block waiting for its unlock. This function may block and so should not be called from interrupt level or while a spin lock is held. Locking the lock recursively from one thread, for read or write, can result in deadlock.
 304  *   @param lock Pointer to the allocated lock. */
 305
 306 #ifdef  IOLOCKS_INLINE
 307 #define IORWLockWrite(l)        lck_rw_lock_exclusive(l)
 308 #else
 309 void    IORWLockWrite( IORWLock * lock);
 310 #endif  /* !IOLOCKS_INLINE */
 311
 312 /*! @function IORWLockUnlock
 313  *   @abstract Unlock a read/write lock.
 314  *   @discussion Undo one call to IORWLockRead or IORWLockWrite. Results are undefined if the caller has not locked the lock. This function may block and so should not be called from interrupt level or while a spin lock is held.
 315  *   @param lock Pointer to the allocated lock. */
 316
 317 #ifdef  IOLOCKS_INLINE
 318 #define IORWLockUnlock(l)       lck_rw_done(l)
 319 #else
 320 void    IORWLockUnlock( IORWLock * lock);
 321 #endif  /* !IOLOCKS_INLINE */
 322
 323 #ifdef XNU_KERNEL_PRIVATE
 324 /*! @enum     IORWLockAssertState
 325  *  @abstract Used with IORWLockAssert to assert the state of a lock.
 326  */
 327 typedef enum {
 328         kIORWLockAssertRead    = LCK_RW_ASSERT_SHARED,
 329         kIORWLockAssertWrite   = LCK_RW_ASSERT_EXCLUSIVE,
 330         kIORWLockAssertHeld    = LCK_RW_ASSERT_HELD,
 331         kIORWLockAssertNotHeld = LCK_RW_ASSERT_NOTHELD
 332 } IORWLockAssertState;
 333
 334 #ifdef IOLOCKS_INLINE
 335 #define IORWLockAssert(l, type) LCK_RW_ASSERT(l, type)
 336 #else
 337 /*! @function   IORWLockAssert
 338  *  @abstract   Assert that a reader-writer lock is either held or not held
 339  *  by the current thread.
 340  *  @discussion Call with a value defined by the IORWLockAssertState type.
 341  *  If the specified lock is not in the state specified by the type argument,
 342  *  then the kernel will panic.
 343  */
 344 void    IORWLockAssert(IORWLock * lock, IORWLockAssertState type);
 345 #endif /* !IOLOCKS_INLINE */
 346 #endif /* !XNU_KERNEL_PRIVATE */
 347
 348 #ifdef __APPLE_API_OBSOLETE
 349
 350 /* The following API is deprecated */
 351
 352 static __inline__ void
 353 IOReadLock( IORWLock * lock)
 354 {
 355         IORWLockRead(lock);
 356 }
 357 static __inline__ void
 358 IOWriteLock(  IORWLock * lock)
 359 {
 360         IORWLockWrite(lock);
 361 }
 362 static __inline__ void
 363 IORWUnlock(   IORWLock * lock)
 364 {
 365         IORWLockUnlock(lock);
 366 }
 367
 368 #endif /* __APPLE_API_OBSOLETE */
 369
 370
 371 /*
 372  * Simple locks. Cannot block while holding a simple lock.
 373  */
 374
 375 #ifdef  IOLOCKS_INLINE
 376 typedef lck_spin_t              IOSimpleLock;
 377 #else
 378 typedef struct _IOSimpleLock    IOSimpleLock;
 379 #endif  /* IOLOCKS_INLINE */
 380
 381 /*! @function IOSimpleLockAlloc
 382  *   @abstract Allocates and initializes a spin lock.
 383  *   @discussion Allocates and initializes a spin lock in general purpose memory. Spin locks provide non-blocking mutual exclusion for synchronization between thread context and interrupt context, or for multiprocessor synchronization, and are supplied by libkern/locks.h. This function may block and so should not be called from interrupt level or while a spin lock is held.  IOSimpleLocks use the global IOKit lock group, IOLockGroup.  To simplify kext debugging and lock-heat analysis, consider using lck_* locks with a per-driver lock group, as defined in kern/locks.h.
 384  *   @result Pointer to the allocated lock, or zero on failure. */
 385
 386 IOSimpleLock * IOSimpleLockAlloc( void );
 387
 388 /*! @function IOSimpleLockFree
 389  *   @abstract Frees a spin lock.
 390  *   @discussion Frees a lock allocated with IOSimpleLockAlloc.
 391  *   @param lock Pointer to the lock. */
 392
 393 void IOSimpleLockFree( IOSimpleLock * lock );
 394
 395 /*! @function IOSimpleLockGetMachLock
 396  *   @abstract Accessor to a Mach spin lock.
 397  *   @discussion Accessor to the Mach spin lock.
 398  *   @param lock Pointer to the allocated lock. */
 399
 400 lck_spin_t * IOSimpleLockGetMachLock( IOSimpleLock * lock);
 401
 402 /*! @function IOSimpleLockInit
 403  *   @abstract Initialize a spin lock.
 404  *   @discussion Initialize a non heap allocated spin lock to the unlocked state. Use this function when your lock is, for example, a member variable. You will need to call IOSimpleLockDestroy when you are finished with the lock to avoid lock group refcount leaks.
 405  *   @param lock Pointer to the lock. */
 406
 407 void IOSimpleLockInit( IOSimpleLock * lock );
 408
 409 /*! @function IOSimpleLockDestroy
 410  *   @abstract De-initializes (destroys) a spin lock initialized with IOSimpleLockInit
 411  *   @discussion Destroy / De-initialize a non heap allocated spin lock, releasing any system resources such as lock group refcounts.
 412  *   @param lock Pointer to the lock. */
 413
 414 void IOSimpleLockDestroy( IOSimpleLock * lock );
 415
 416 /*! @function IOSimpleLockLock
 417  *   @abstract Lock a spin lock.
 418  *  @discussion Lock the spin lock. If the lock is held, spin waiting for its unlock. Spin locks disable preemption, cannot be held across any blocking operation, and should be held for very short periods. When used to synchronize between interrupt context and thread context they should be locked with interrupts disabled - IOSimpleLockLockDisableInterrupt() will do both. Locking the lock recursively from one thread will result in deadlock.
 419  *   @param lock Pointer to the lock. */
 420
 421 #ifdef  IOLOCKS_INLINE
 422 #define IOSimpleLockLock(l)     lck_spin_lock(l)
 423 #else
 424 void IOSimpleLockLock( IOSimpleLock * lock );
 425 #endif  /* !IOLOCKS_INLINE */
 426
 427
 428 /*! @function IOSimpleLockTryLock
 429  *   @abstract Attempt to lock a spin lock.
 430  *  @discussion Lock the spin lock if it is currently unlocked, and return true. If the lock is held, return false. Successful calls to IOSimpleLockTryLock should be balanced with calls to IOSimpleLockUnlock.
 431  *   @param lock Pointer to the lock.
 432  *   @result True if the lock was unlocked and is now locked by the caller, otherwise false. */
 433
 434 #ifdef  IOLOCKS_INLINE
 435 #define IOSimpleLockTryLock(l)  lck_spin_try_lock(l)
 436 #else
 437 boolean_t IOSimpleLockTryLock( IOSimpleLock * lock );
 438 #endif  /* !IOLOCKS_INLINE */
 439
 440 /*! @function IOSimpleLockUnlock
 441  *   @abstract Unlock a spin lock.
 442  *   @discussion Unlock the lock, and restore preemption. Results are undefined if the caller has not locked the lock.
 443  *   @param lock Pointer to the lock. */
 444
 445 #ifdef  IOLOCKS_INLINE
 446 #define IOSimpleLockUnlock(l)   lck_spin_unlock(l)
 447 #else
 448 void IOSimpleLockUnlock( IOSimpleLock * lock );
 449 #endif  /* !IOLOCKS_INLINE */
 450
 451 #ifdef XNU_KERNEL_PRIVATE
 452 /*! @enum     IOSimpleLockAssertState
 453  *  @abstract Used with IOSimpleLockAssert to assert the state of a lock.
 454  */
 455 typedef enum {
 456         kIOSimpleLockAssertOwned    = LCK_ASSERT_OWNED,
 457         kIOSimpleLockAssertNotOwned = LCK_ASSERT_NOTOWNED
 458 } IOSimpleLockAssertState;
 459
 460 #ifdef IOLOCKS_INLINE
 461 #define IOSimpleLockAssert(l, type) LCK_SPIN_ASSERT(l, type)
 462 #else
 463 /*! @function   IOSimpleLockAssert
 464  *  @abstract   Assert that spinlock is either held or not held by current thread.
 465  *  @discussion Call with either kIOSimpleLockAssertOwned or kIOSimpleLockAssertNotOwned.
 466  *  Panics the kernel if the lock is not owned if called with
 467  *  kIOSimpleLockAssertOwned and vice-versa.
 468  */
 469 void    IOSimpleLockAssert(IOSimpleLock *lock, IOSimpleLockAssertState type);
 470 #endif /* !IOLOCKS_INLINE */
 471 #endif /* !XNU_KERNEL_PRIVATE */
 472
 473 #if __LP64__
 474 typedef boolean_t IOInterruptState;
 475 #else
 476 typedef long int IOInterruptState;
 477 #endif
 478
 479 /*! @function IOSimpleLockLockDisableInterrupt
 480  *   @abstract Lock a spin lock.
 481  *   @discussion Lock the spin lock. If the lock is held, spin waiting for its unlock. Simple locks disable preemption, cannot be held across any blocking operation, and should be held for very short periods. When used to synchronize between interrupt context and thread context they should be locked with interrupts disabled - IOSimpleLockLockDisableInterrupt() will do both. Locking the lock recursively from one thread will result in deadlock.
 482  *   @param lock Pointer to the lock. */
 483
 484 static __inline__
 485 IOInterruptState
 486 IOSimpleLockLockDisableInterrupt( IOSimpleLock * lock )
 487 {
 488         IOInterruptState    state = ml_set_interrupts_enabled( false );
 489         IOSimpleLockLock( lock );
 490         return state;
 491 }
 492
 493 /*! @function IOSimpleLockUnlockEnableInterrupt
 494  *   @abstract Unlock a spin lock, and restore interrupt state.
 495  *   @discussion Unlock the lock, and restore preemption and interrupts to the state as they were when the lock was taken. Results are undefined if the caller has not locked the lock.
 496  *   @param lock Pointer to the lock.
 497  *   @param state The interrupt state returned by IOSimpleLockLockDisableInterrupt() */
 498
 499 static __inline__
 500 void
 501 IOSimpleLockUnlockEnableInterrupt( IOSimpleLock * lock,
 502     IOInterruptState state )
 503 {
 504         IOSimpleLockUnlock( lock );
 505         ml_set_interrupts_enabled( state );
 506 }
 507
 508 #ifdef __cplusplus
 509 } /* extern "C" */
 510 #endif
 511
 512 #endif /* !__IOKIT_IOLOCKS_H */