Hey,
I want to embed V8 in my game engine, mainly because I prefer it's C++
API over that of SpiderMonkey's. However I'm having some thoughts
about thread-safety, since my engine would be executing each script in
its own thread.
I know that only a single thread can use V8 at a time, and that you
use the v8::Locker to lock access to V8 per-thread basis. This is all
good for me, because I can still unlock the thread if I have to wait
for some resource that is not related to V8. For sake of simplicity,
let's say I have to sleep for 2 seconds in a script, I could do this
by:
{
v8::Unlocker ul;
Sleep(2);
}
And while the thread sleeps, other scripts could still execute since
v8 is unlocked. However what I'm concerned about is how will
HandleScopes scope with this. Consider the following example:
{
v8::Locker l;
v8::HandleScope handle_scope;
{
v8::Unlocker ul;
Sleep(2);
}
v8::Local<v8::Value> str = v8::String::New("foobar");
// For sake of not having to write almost two identical functions,
// assume that ONLY thread 1 does this:
{
v8::Unlocker ul;
Sleep(2);
}
std::string s = String::AsciiValue ascii(str);
// And thread 2 would ONLY do this:
return;
}
Let's say that two threads run this same script. When the first thread
unlocks for the first time and goes to sleep, the 2nd thread will
create a new HandleScope, and thus all consecutive allocations are
done on the 2nd thread's handle scope. So when thread 2 goes to sleep,
and thread 1 wakes up, it'll create a new String using the HandleScope
that was created on the thread 2 while thread 1 was sleeping. Now
thread 1 will go to sleep again, and thread 2 will wake up. At this
point thread 2 simply returns, and since the HandleScope goes out of
scope, it'll free all the locals that it had allocated, _including_
the string created in thread 1 (since it was allocated using the wrong
HandleScope). After this the control returns back to the thread 1,
which tries to use the already de-allocated value, and probably crash
because of that.
Am I getting this right? If I am, is there any plausible way to get
around this, because I really need to be able to run multiple scripts
at the same time, but I have plenty of scripts that would block until
some sort of an event happens in the game, and other scripts need to
be able to run during the time the script waits.
Regards,
Reko Tiira
--
v8-users mailing list
[email protected]
http://groups.google.com/group/v8-users
