Changeset 179609 in webkit for trunk/Source/JavaScriptCore/runtime/VM.cpp

Timestamp:

Feb 4, 2015, 10:00:05 AM (10 years ago)

Author:

[email protected]

Message:

Remove concept of makeUsableFromMultipleThreads().
<​https://webkit.org/b/141221>

Reviewed by Mark Hahnenberg.

Source/JavaScriptCore:

Currently, we rely on VM::makeUsableFromMultipleThreads() being called before we
start acquiring the JSLock and entering the VM from different threads.
Acquisition of the JSLock will register the acquiring thread with the VM's thread
registry if not already registered. However, it will only do this if the VM's
thread specific key has been initialized by makeUsableFromMultipleThreads().

This is fragile, and also does not read intuitively because one would expect to
acquire the JSLock before calling any methods on the VM. This is exactly what
JSGlobalContextCreateInGroup() did (i.e. acquire the lock before calling
makeUsableFromMultipleThreads()), but is wrong. The result is that the invoking
thread will not have been registered with the VM during that first entry into
the VM.

The fix is to make it so that we initialize the VM's thread specific key on
construction of the VM's MachineThreads registry instead of relying on
makeUsableFromMultipleThreads() being called. With this, we can eliminate
makeUsableFromMultipleThreads() altogether.

Performance results are neutral in aggregate.

• API/JSContextRef.cpp:

(JSGlobalContextCreateInGroup):

• heap/MachineStackMarker.cpp:

(JSC::MachineThreads::MachineThreads):
(JSC::MachineThreads::~MachineThreads):
(JSC::MachineThreads::addCurrentThread):
(JSC::MachineThreads::removeThread):
(JSC::MachineThreads::gatherConservativeRoots):
(JSC::MachineThreads::makeUsableFromMultipleThreads): Deleted.

• heap/MachineStackMarker.h:
• runtime/VM.cpp:

(JSC::VM::sharedInstance):

• runtime/VM.h:

(JSC::VM::makeUsableFromMultipleThreads): Deleted.

Source/WebCore:

No new tests.

• bindings/js/JSDOMWindowBase.cpp:

(WebCore::JSDOMWindowBase::commonVM):

File:

• trunk/Source/JavaScriptCore/runtime/VM.cpp (modified) (1 diff)

trunk/Source/JavaScriptCore/runtime/VM.cpp

@@ -358 +358 @@
     GlobalJSLock globalLock;
     VM*& instance = sharedInstanceInternal();
-    if (!instance) {
+    if (!instance)
         instance = adoptRef(new VM(APIShared, SmallHeap)).leakRef();
-        instance->makeUsableFromMultipleThreads();
-    }
     return *instance;
 }