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