On Fri, 8 Dec 2023 17:12:29 GMT, Sergey Bylokhov <s...@openjdk.org> wrote:
>> The fix for a regression caused by the >> https://bugs.openjdk.org/browse/JDK-6508941. it does not take into account >> RPC_E_CHANGED_MODE when COM was already initialized using >> COINIT_MULTITHREADED mode. >> >> @aivanov-jdk please take a look. > > Sergey Bylokhov has updated the pull request incrementally with one > additional commit since the last revision: > > Update src/java.desktop/windows/native/libawt/windows/awt_Desktop.cpp > > date > > Co-authored-by: Alexey Ivanov <alexey.iva...@oracle.com> > > The confusion could come from #14898 where [#14898 > > (comment)](https://github.com/openjdk/jdk/pull/14898#issuecomment-1748967705) > > us from calling DirectSound API which supports both MTA and STA. > > Would like to clarify difference between this and that patch: this bug shows > that some api does not support MTA mode, and intentionally requests the STA - > so our code was broken by some external call -> enable COM+MTA. > > At the same time the [patch](https://github.com/openjdk/jdk/pull/14898) may > change the current mode of the thread from STA to MTA and that seems could > break all code executed after? How come? It can't change: once COM is initialised on a thread, its threading model cannot be changed. This is what `RPC_E_CHANGED_MODE` error code conveys, in other words you request initialising COM in a threading model that's different the model COM has been initialised previously. The code in #14898 always initialises COM in MTA. If COM is initialised in STA, the thread and COM remains in STA. The only difference is that it is still *valid* to call the DirectSound API because the API supports both MTA and STA modes. This case corresponds to option 3 in [this comment](https://github.com/openjdk/jdk/pull/14898#issuecomment-1748967705). In other words the workflow in case 3 of JDK-8301846 / PR 14898: // some app code COM -> STA = S_OK // more code AudioSystem.getMixerInfo(): COM -> MTA = RPC_E_CHANGED_MODE // threading model still STA DirectSoundEnumerateW / DirectSoundCaptureEnumerateW skip ::CoUninitialize() // thread continues with COM in STA (I was even inclined to use [the same approach](https://github.com/openjdk/jdk/pull/14898#discussion_r1276539431) with a worker thread which initialises COM to avoid dealing with `RPC_E_CHANGED_MODE`. It was only after I had received [clarification from Microsoft](https://github.com/openjdk/jdk/pull/14898#issuecomment-1721687912) that I changed my opinion because (a) Initialising and uninitialising COM aren't heavy; (b) DirectSound APIs support both MTA and STA.) ------------- PR Comment: https://git.openjdk.org/jdk/pull/17010#issuecomment-1850737151
