src/dyldLock.h

   1 /* -*- mode: C++; c-basic-offset: 4; tab-width: 4 -*-
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  24
  25
  26 #ifndef __DYLDLOCK__
  27 #define __DYLDLOCK__
  28
  29 //
  30 // This file contains the syncronization utilities used by dyld to be thread safe.
  31 // Access to all dyld data structures is protected by a reader-writer lock.
  32 // This lock allows multiple "reader" threads to access dyld data structures at
  33 // the same time.  If there is a "writer" thread, it is the only thread allowed
  34 // access to dyld data structures.
  35 //
  36 // The implementation of all dyld API's must acquire the global lock around accesses
  37 // to dyld's data structures.  This is done using the macros DYLD_*_LOCK_THIS_BLOCK.
  38 // Example:
  39 //
  40 //  void dyld_api_modifying_dyld() {
  41 //              DYLD_WRITER_LOCK_THIS_BLOCK;
  42 //              // free to do stuff here
  43 //              // that modifies dyld data structures
  44 //      }
  45 //
  46 //  void dyld_api_examinging_dyld() {
  47 //              DYLD_READER_LOCK_THIS_BLOCK
  48 //              // can only do stuff here
  49 //              // that examines but does not modify dyld data structures
  50 //      }
  51 //
  52 //  void dyld_api_state_free() {
  53 //              DYLD_NO_LOCK_THIS_BLOCK
  54 //              // can only do stuff here
  55 //              // that does not require locking
  56 //      }
  57 //
  58
  59
  60 #define DYLD_READER_LOCK_THIS_BLOCK             LockReaderHelper _dyld_lock;
  61 #define DYLD_WRITER_LOCK_THIS_BLOCK             LockWriterHelper _dyld_lock;
  62 #define DYLD_NO_LOCK_THIS_BLOCK
  63
  64 // used by dyld wrapper functions in libSystem
  65 class LockReaderHelper
  66 {
  67 public:
  68         LockReaderHelper() __attribute__((visibility("hidden")));
  69         ~LockReaderHelper() __attribute__((visibility("hidden")));
  70 };
  71
  72 // used by dyld wrapper functions in libSystem
  73 class LockWriterHelper
  74 {
  75 public:
  76         LockWriterHelper() __attribute__((visibility("hidden")));
  77         ~LockWriterHelper() __attribute__((visibility("hidden")));
  78 };
  79
  80 // used by lazy binding
  81 extern void lockForLazyBinding() __attribute__((visibility("hidden")));
  82 extern void unlockForLazyBinding() __attribute__((visibility("hidden")));
  83
  84
  85
  86 #endif // __DYLDLOCK__
  87