mono/utils/mono-threads-mach-helper.c

   1 /**
   2  * \file
   3  * ObjectiveC hacks to improve our changes with thread shutdown
   4  *
   5  * Author:
   6  *      Rodrigo Kumpera (kumpera@gmail.com)
   7  *
   8  * (C) 2014 Xamarin Inc
   9  */
  10
  11 #if defined(__MACH__)
  12
  13 #include "config.h"
  14 #include <glib.h>
  15 #include <stdio.h>
  16 #include <objc/runtime.h>
  17 #include <objc/message.h>
  18 #include <mono/utils/mono-compiler.h>
  19 #include <mono/utils/mono-publib.h>
  20
  21 /*
  22  * We cannot include mono-threads.h as this includes io-layer internal types
  23  * which conflicts with objc.
  24  * Hence the hack here.
  25 */
  26 void mono_threads_init_dead_letter (void);
  27 void mono_threads_install_dead_letter (void);
  28 MONO_API void
  29 mono_thread_info_detach (void);
  30
  31 static Class nsobject, nsthread, mono_dead_letter_class;
  32 static SEL dealloc, release, currentThread, threadDictionary, init, alloc, objectForKey, setObjectForKey;
  33 static id mono_dead_letter_key;
  34
  35 /*
  36  * Our Mach bindings have a problem in that they might need to attach
  37  * the runtime after the the user tls keys have been destroyed.
  38  *
  39  * This happens when a bound object is retained by NSThread, which is
  40  * released very late in the TLS cleanup process.
  41  *
  42  * At that point, attaching the runtime leaves us in no position to
  43  * detach it later using TLS destructors as pthread is done with user
  44  * keys. This leaves us with a dead thread registered, which can cause
  45  * all sorts of terrible problems.
  46  *
  47  * The tipical crash is when another thread is created at the exact
  48  * same address of the previous one, cause thread registration to abort
  49  * due to duplicate entries.
  50  *
  51  * So what do we do here?
  52  *
  53  * Experimentation showns that threadDictionary is destroied after the
  54  * problematic keys, so we add our dead letter object as an aditional
  55  * way to be notified of thread death.
  56  */
  57 static void
  58 mono_dead_letter_dealloc (id self, SEL _cmd)
  59 {
  60         struct objc_super super;
  61         super.receiver = self;
  62 #if !defined(__cplusplus) && !__OBJC2__
  63         super.class = nsobject;
  64 #else
  65         super.super_class = nsobject;
  66 #endif
  67         void (*objc_msgSendSuper_op)(struct objc_super *, SEL) = (void (*)(struct objc_super *, SEL)) objc_msgSendSuper;
  68         objc_msgSendSuper_op (&super, dealloc);
  69
  70         mono_thread_info_detach ();
  71 }
  72
  73 void
  74 mono_threads_install_dead_letter (void)
  75 {
  76         id cur, dict;
  77
  78         /*
  79          * See the 'Dispatch Objective-C Messages Using the Method Function’s Prototype' section in
  80          * the '64-Bit Transition Guide for Cocoa Touch' as to why this is required.
  81          *
  82          * It doesn't hurt on other architectures either, so no need to #ifdef it only for ARM64.
  83          */
  84
  85         id (*id_objc_msgSend)(id, SEL) = (id (*)(id, SEL)) objc_msgSend;
  86         id (*id_objc_msgSend_id)(id, SEL, id) = (id (*)(id, SEL, id)) objc_msgSend;
  87         void (*objc_msgSend_id_id)(id, SEL, id, id) = (void (*)(id, SEL, id, id)) objc_msgSend;
  88
  89         cur = id_objc_msgSend ((id)nsthread, currentThread);
  90         if (!cur)
  91                 return;
  92         dict = id_objc_msgSend (cur, threadDictionary);
  93         if (dict && id_objc_msgSend_id (dict, objectForKey, mono_dead_letter_key) == nil) {
  94                 id value = id_objc_msgSend (id_objc_msgSend ((id)mono_dead_letter_class, alloc), init);
  95
  96                 objc_msgSend_id_id (dict, setObjectForKey, value, mono_dead_letter_key);
  97
  98                 id_objc_msgSend (value, release);
  99         }
 100 }
 101
 102 void
 103 mono_threads_init_dead_letter (void)
 104 {
 105         id nsstring = (id) objc_getClass ("NSString");
 106         id nsautoreleasepool = (id) objc_getClass ("NSAutoreleasePool");
 107         SEL stringWithUTF8String = sel_registerName ("stringWithUTF8String:");
 108         SEL retain = sel_registerName ("retain");
 109         id pool;
 110
 111         nsthread = (Class)objc_getClass ("NSThread");
 112         nsobject = (Class)objc_getClass ("NSObject");
 113
 114         init = sel_registerName ("init");
 115         alloc = sel_registerName ("alloc");
 116         release = sel_registerName ("release");
 117         dealloc = sel_registerName ("dealloc");
 118
 119
 120         currentThread = sel_registerName ("currentThread");
 121         threadDictionary = sel_registerName ("threadDictionary");
 122         setObjectForKey = sel_registerName ("setObject:forKey:");
 123         objectForKey = sel_registerName ("objectForKey:");
 124
 125         // define the dead letter class
 126         mono_dead_letter_class = objc_allocateClassPair (nsobject, "MonoDeadLetter", 0);
 127         class_addMethod (mono_dead_letter_class, dealloc, (IMP)mono_dead_letter_dealloc, "v@:");
 128         objc_registerClassPair (mono_dead_letter_class);
 129
 130         id (*id_objc_msgSend)(id, SEL) = (id (*)(id, SEL)) objc_msgSend;
 131
 132         // create the dict key
 133         pool = id_objc_msgSend (id_objc_msgSend (nsautoreleasepool, alloc), init);
 134
 135         id (*objc_msgSend_char)(id, SEL, const char*) = (id (*)(id, SEL, const char*)) objc_msgSend;
 136         mono_dead_letter_key = objc_msgSend_char (nsstring, stringWithUTF8String, "mono-dead-letter");
 137
 138         id_objc_msgSend (mono_dead_letter_key, retain);
 139         id_objc_msgSend (pool, release);
 140 }
 141 #endif