What does idle state mean?
The code my users run never terminates, i.e., it permanently spins waiting
for events, so the stack depth never goes to 0.
None of the code is async, as the version of spidermonkey used did not have
it.
They potentially call some native functions (sleep which literally does
thread::sleep in C++) etc, but otherwise the code is non-async and never
terminating, and always at non-zero stack depth.
This sounds like the isolate is never idle, hence there is no nice way to
do this?
Surely chome somehow delivers events/setTimeout timers even if the users
code has a while(true) {} ?
I assume node does it too somehow?
I guess I could check for events to deliver in every native function I
expose, but that feels a bit yuck.
I could also continue doing it in the interrupt, the docs say don't do it,
but it seems to work and nothing panics (I have not run very complicated
code however, not sure at what point it breaks)
Thanks.
On Tuesday, 22 April 2025 at 02:26:21 UTC+1 d3c...@gmail.com wrote:
> On Mon, Apr 21, 2025 at 6:21 PM J Decker <d3c...@gmail.com> wrote:
>
>> You will have to wait for the JS stack to be idle for events to get
>> dispatched... even promises are only dispatched from an idle state in the
>> JS stack (where it has returned fully).
>>
>> You can call any JS functions in the initialization callback - but you
>> cannot use the isolate or make a handle scope in not the right thread... so
>> you have to wait for the uv_async_init'ed callback to be triggered before
>> doing queued work.
>>
>> If this isn't sufficient and you really need parallel or injected
>> execution - for node there's a worker-thread module ; but the eventual
>> results have to be dispatched at the idle level still...
>> https://github.com/laverdet/isolated-vm for example... (this is also a
>> C++ thread that deals directly with allocating and managing isolates)
>>
>> you use `uv_async_init` once, which initialized a uv_async_t handle to be
>> associated with a loop. You then use uv_async_send( handle ); which
>> triggers dispatching to that routine; you will have to create a handle
>> scope in that callback before doing JS functions. The handle can only be
>> closed in the main thread also. The work can be queued to internal
>> tracking, and when the async callback runs, it just checks for outstanding
>> work, and calls appropriate JS callbacks.
>>
>
> By default - initializing handles for for uv_async_send to work - they add
> a reference that keeps (node) running (I see this isn't actually a node
> specific thread though)... you can async_unref( handle ) and that will keep
> it schedulable, but not hold the process open. (may times like opening a
> server socket, you'd want the process to not exit until that socket is
> closed (which is probably never) but other situations might not be critical
> enough to hold the process - my GUI interface has gone this way and the
> window event dispatch don't actually keep the process open; but then I
> ended up with a keep-alive setTimeout()... Just thought it might be useful
> to note.
>
>
>>
>> On Mon, Apr 21, 2025 at 9:51 AM jmr <audrius.b...@gmail.com> wrote:
>>
>>> Ok, seems that I CAN call js functions from within RequestInterrupt,
>>> things seem to work.
>>>
>>> I guess I'm confused what this means in that case: "Registered
>>> |callback| must not reenter interrupted Isolate."
>>>
>>>
>>>
>>> On Monday, 21 April 2025 at 17:41:21 UTC+1 jmr wrote:
>>>
>>>> I'm porting an application that is using SpiderMonkey for embedding,
>>>> and I have a few questions.
>>>>
>>>> One of the things my application does is, it allows user (in
>>>> javascript) to register for events:
>>>>
>>>> func handler(...) { {}
>>>> registerEventHandler("evetName", handler);
>>>>
>>>> In C++, I then store these handlers to be called later once the event
>>>> arrives.
>>>>
>>>> Once the event arrives (different thread than isolate is running on), I
>>>> store it in a pending event list for the runtime (isolate), I then
>>>> call JS_RequestInterruptCallback which interrupts the execution of the
>>>> runtime (isolate), and drops into my C++ interrupt callback.
>>>>
>>>> From my C++ callback, I check for pending events, and call the user
>>>> provided functions (re-entering the isolate) delivering the events, and
>>>> resume execution to the user.
>>>>
>>>> Seems that with v8, I can get quite close to this, except
>>>> isolate->RequestInterrupt does not allow re-entering the isolate/calling
>>>> user code, making this not work.
>>>>
>>>> I tried using EnqueueMicrotask but seems those are never delivered
>>>> automatically unless the script stops, or I call
>>>> PerformMicrotaskCheckpoint
>>>> (which then ends up on the wrong, calling thread)
>>>>
>>>> I tried posting a task to the platform
>>>> (platform->GetForegroundTaskRunner(isolate)->PostTask), but given the
>>>> script is long lived, I don't think this ever gets delivered.
>>>>
>>>> I tried using Locker(isolate) + Isolate::Scope(isolate)
>>>> + isolate->GetCurrentContext() from the event thread, and then calling the
>>>> callbacks, but this crashes non-deterministically, sometimes with "Invoke
>>>> in DisallowJavascriptExecutionScope".
>>>>
>>>> Any guidance is appreciated.
>>>> Thanks.
>>>>
>>>> --
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