[Lldb-commits] [lldb] ffc0533 - [lldb] Use the non-locking variant of objc_copyRealizedClassList

[Jonas Devlieghere via lldb-commits]

Author: Jonas Devlieghere
Date: 2021-06-25T15:02:49-07:00
New Revision: ffc0533855871f4c784f6535044ce7c2bd076392

URL: https://github.com/llvm/llvm-project/commit/ffc0533855871f4c784f6535044ce7c2bd076392
DIFF: https://github.com/llvm/llvm-project/commit/ffc0533855871f4c784f6535044ce7c2bd076392.diff

LOG: [lldb] Use the non-locking variant of objc_copyRealizedClassList

Avoid standing the Objective-C runtime lock by calling
objc_copyRealizedClassList_nolock instead of objc_copyRealizedClassList.

We already guarantee that no other threads can run while we're running
this utility expression, similar to when we parse the data ourselves
from the gdb_objc_realized_classes struct.

Worst case this will crash if the list is getting edited, which won't do
any harm and we'll just try again later.

Differential revision: https://reviews.llvm.org/D104951

Added: 
    

Modified: 
    lldb/source/Plugins/LanguageRuntime/ObjC/AppleObjCRuntime/AppleObjCRuntimeV2.cpp

Removed: 
    


################################################################################
diff  --git a/lldb/source/Plugins/LanguageRuntime/ObjC/AppleObjCRuntime/AppleObjCRuntimeV2.cpp b/lldb/source/Plugins/LanguageRuntime/ObjC/AppleObjCRuntime/AppleObjCRuntimeV2.cpp
index 069368c8e058..a3a0827cfe65 100644
--- a/lldb/source/Plugins/LanguageRuntime/ObjC/AppleObjCRuntime/AppleObjCRuntimeV2.cpp
+++ b/lldb/source/Plugins/LanguageRuntime/ObjC/AppleObjCRuntime/AppleObjCRuntimeV2.cpp
@@ -172,7 +172,7 @@ static const char *g_get_dynamic_class_info2_body = R"(
 extern "C" {
     int printf(const char * format, ...);
     void free(void *ptr);
-    Class* objc_copyRealizedClassList(unsigned int *outCount);
+    Class* objc_copyRealizedClassList_nolock(unsigned int *outCount);
     const char* objc_debug_class_getNameRaw(Class cls);
 }
 
@@ -199,7 +199,7 @@ __lldb_apple_objc_v2_get_dynamic_class_info2(void *gdb_objc_realized_classes_ptr
     ClassInfo *class_infos = (ClassInfo *)class_infos_ptr;
 
     uint32_t count = 0;
-    Class* realized_class_list = objc_copyRealizedClassList(&count);
+    Class* realized_class_list = objc_copyRealizedClassList_nolock(&count);
     DEBUG_PRINTF ("count = %u\n", count);
 
     uint32_t idx = 0;
@@ -668,7 +668,7 @@ AppleObjCRuntimeV2::AppleObjCRuntimeV2(Process *process,
   static const ConstString g_gdb_object_getClass("gdb_object_getClass");
   m_has_object_getClass = HasSymbol(g_gdb_object_getClass);
   static const ConstString g_objc_copyRealizedClassList(
-      "objc_copyRealizedClassList");
+      "objc_copyRealizedClassList_nolock");
   m_has_objc_copyRealizedClassList = HasSymbol(g_objc_copyRealizedClassList);
 
   RegisterObjCExceptionRecognizer(process);