RFR: JDK-8298908: Instrument Metaspace for ASan [v12]

[Ioi Lam]

On Thu, 12 Jan 2023 07:40:05 GMT, Thomas Stuefe <stuefe at openjdk.org> wrote:

>> src/hotspot/share/memory/metaspace/chunkManager.cpp line 308:
>> 
>>> 306:   }
>>> 307: 
>>> 308:   if (enlarged) {
>> 
>> What's the reason of calling the ASAN functions outside of the lock?
>> 
>> Will we have a race condition if two threads call ChunkManager::attempt_enlarge_chunk() at the same time and get to here out of order? @tstuefe
>
> To be enlarged chunk belongs to the class loader already, and we are inside the class loader metaspace lock.

If there's no particular reason to do it outside of the lock, I would prefer to have the ASAN call while holding the lock. That way you don't need to worry about race conditions.


MutexLocker fcl(Metaspace_lock, Mutex::_no_safepoint_check_flag);
old_level = c->level();
enlarged = c->vsnode()->attempt_enlarge_chunk(c, &_chunks);
ASAN_UNPOISON_MEMORY_REGION(....);

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PR: https://git.openjdk.org/jdk/pull/11702