>
> Are you assuming that the worker is terminated while it's calling
> DoSomethingElseWithV8()? If yes, why does HasCaught() not return true? If
> no, what's a problem of continuing execution?
No, the worker is terminated while DoSomethingWithV8 (without "Else"), and
Blink continues running more V8 code at DoSomethingElseWithV8. Two pieces
of code run consecutively.
Worker thread (worker isolate):
{
v8::TryCatch try_catch(isolate);
DoSomethingWithV8(); // The Isolate terminates here.
if (try_catch.HasCaught()) { // => true due to termination
// Handle error or termination.
return;
}
}
{
v8::TryCatch try_catch(isolate);
DoSomethingElseWithV8(); // V8 APIs fail because the Isolate is
terminating.
if (try_catch.HasCaught()) { // => false because no new exception is
thrown inside the v8::TryCatch.
return; // Blink doesn't reach here.
}
// Blink reach here instead. :(
}
IIUC, the second try_catch.HasCaught() doesn't return true because there is
no new exception thrown inside the v8::TryCatch scope, although V8 APIs
fail inside DoSomethingElseWithV8 due to a pending termination exception.
Cheers,
Yuki Shiino
2018年11月8日(木) 3:18 Kentaro Hara <hara...@chromium.org>:
> Sorry, I'm not sure if I understand your example...
>
>
> On Wed, Nov 7, 2018 at 2:21 AM Yutaka Hirano <yhir...@chromium.org> wrote:
>
>> +ricea@
>>
>> On Wed, Nov 7, 2018 at 6:44 PM Yuki Shiino <yukishi...@chromium.org>
>> wrote:
>>
>>> Hi V8-team and platform-architecture-dev,
>>>
>>> TL;DR: We'd like to extend v8::TryCatch APIs a little.
>>>
>>> We're having an issue how to handle worker termination, i.e. v8::Isolate
>>> termination. Roughly speaking, the situation is like below.
>>>
>>> Main thread:
>>> v8::Isolate* worker_isolate = ...;
>>> worker_isolate->TerminateExecution(); // Terminates the worker
>>> isolate.
>>>
>>> Worker thread (worker isolate):
>>> v8::TryCatch try_catch(isolate);
>>> DoSomethingWithV8(); // The Isolate terminates here.
>>> if (try_catch.HasCaught()) { // => true due to termination
>>> // Handle error or termination.
>>> return;
>>> }
>>>
>>> No problem so far. Worker thread MUST NOT run any V8 code no longer
>>> because the Isolate is terminating. However, Blink is not perfect, and
>>> it's pretty tough for Blink to stop everything with 100% correctness.
>>> Occasionally (or rarely) Blink continues running more V8 code like below.
>>>
>>> Worker thread (worker isolate):
>>> v8::TryCatch try_catch(isolate);
>>> DoSomethingElseWithV8();
>>> if (try_catch.HasCaught()) { // => false because no new exception
>>> is thrown inside the v8::TryCatch.
>>> return; // Blink doesn't reach here.
>>> }
>>> // Blink reach here instead. :(
>>>
>>> If v8::TryCatch::HasCaught() returned true, Blink would be able to
>>> handle it as error and Blink would work much better than now (Blink is now
>>> crashing).
>>>
>>
> Are you assuming that the worker is terminated while it's calling
> DoSomethingElseWithV8()? If yes, why does HasCaught() not return true? If
> no, what's a problem of continuing execution?
>
>
>
>>> So, proposals here are something like below (not yet so concrete).
>>>
>>> a) Make v8::TryCatch::HasCaught() return true if there already exists a
>>> pending exception. (Maybe this is no good.)
>>> b) Make a new API like v8::TryCatch::HasPendingException() and make it
>>> return true. Blink rewrites all HasCaught() to the new one.
>>>
>>> Similarly,
>>>
>>> a2) Make v8::TryCatch::Exception() return a pending exception if there
>>> already exists.
>>> b2) Make a new API like v8::TryCatch::PendingException() and make it
>>> return a thrown exception or pending exception in the isolate if any.
>>> Blink rewrites all Exception() to the new one.
>>>
>>> What do you think of the issue and proposals?
>>>
>>> Cheers,
>>> Yuki Shiino
>>>
>>> --
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>> <https://groups.google.com/a/chromium.org/d/msgid/platform-architecture-dev/CABihn6ER8q9QABC3ROCSkm6V4w%2BDb0xEqRvjgzwBpMG9DmiG1Q%40mail.gmail.com?utm_medium=email&utm_source=footer>
>> .
>>
>
>
> --
> Kentaro Hara, Tokyo, Japan
>
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