Hi, On Thu, Oct 11, 2018 at 11:00 AM Lars Hansen <[email protected]> wrote:
>> 1. Thread A sends a 1k shared block to Thread B via >> `postMessage` >> 2. Thread B writes to various locations in that block directly >> (not via `Atomics.store`) >> 3. Thread B does a `postMessage` to Thread A (without >> referencing the block in the `postMessage`) >> 4. Thread A receives the message and reads data from the block >> (not via `Atomics.load`) >> >> ...am I correct that in Step 4 it's guaranteed that thread A >> **will** reliably see the writes to that block by Thread B from >> Step 2, because the `postMessage` was a "synchronization edge" >> ensuring (amongst other things) that CPU L1d caches are >> up-to-date, etc.? > > Yes, that was the intent of that language. The writes to the > memory should happen-before the postMessage and the > receive-message should happen-before the reads. > >> Similarly, if (!) I'm reading it correctly, in your Mandlebrot >> example, you have an `Atomics.wait` on a single location in a >> shared block, and when the thread wakes up it seems to assume >> other data in the block (not in the `wait` range) can >> reliably be read directly. That's also a "synchronization edge"? > > Yes, same argument. The writes happen-before the wake, and the > wakeup of the wait happens-before the reads. > > All of this is by intent so as to allow data to be written and > read with cheap unsynchronized writes and reads, and then for > the (comparatively expensive) synchronization to ensure proper > observability. Fantastic, that's exactly what I was hoping. Thank you again! -- T.J. Crowder _______________________________________________ es-discuss mailing list [email protected] https://mail.mozilla.org/listinfo/es-discuss
