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