clarify a bit the I/O story

[web.git] / personal / _posts / 2018-07-13-arc-synchronization.md

diff --git a/personal/_posts/2018-07-13-arc-synchronization.md b/personal/_posts/2018-07-13-arc-synchronization.md
index 50a518c6ec848d23080ca88349bb35bd65dc5daf..2e8f7eab1d2510c2cb57d68a308552dccfdc920f 100644 (file)
--- a/personal/_posts/2018-07-13-arc-synchronization.md
+++ b/personal/_posts/2018-07-13-arc-synchronization.md
@@ -157,10 +157,10 @@ fn main() {
 {% endhighlight %}
 This program, finally, is free of data races and hence has no undefined behavior and is guaranteed to print "Hello World!".
 
-They key point is that *when an `Acquire` read reads from a `Release` write, an order is induced between these two accesses*.
+They key point is that *when a `load(Acquire)` reads from a `store(_, Release)`, an order is induced between these two accesses*.
 We also say that the two accesses *synchronize*.
 Together with the per-thread order, this means we have an order between the `DATA = Some(...)` in the first thread and the load of `DATA` in the second thread, through the accesses to `FLAG`.
-Intuitively, the `Release` write in the first thread "releases" everything that has been changed by this thread so far, and the `Acquire` read in the second thread then "acquires" all that data and makes it accessible for access later in this thread.
+Intuitively, the `store(_, Release)` in the first thread "releases" everything that has been changed by this thread so far, and the `load(Acquire)` in the second thread then "acquires" all that data and makes it accessible for access later in this thread.
 
 Now, most of the time a `Mutex` or `RwLock` is good enough to protect your data against concurrent accesses, so you do not have to worry about such details.
 (And, thanks to Rust thread safety guarantees, you never have to worry about such details in safe code!)
@@ -188,3 +188,5 @@ In that paper, we did not (yet) have the tools to reason realistically about the
 This is one of the simplifications we made compared to real Rust to make the verification feasible.
 We were realistic enough to find [another bug]({{ site.baseurl }}{% post_url 2017-06-09-mutexguard-sync %}), but not realistic enough for this one.
 Hai and Jacques-Henri are currently working on remedying this particular simplification by extending the first RustBelt paper to also cover weak memory, and that's when they ran into this problem.
+
+**Update:** Turns out Servo has a [copy of `Arc`](https://doc.servo.org/servo_arc/index.html) that [has the same problem](https://github.com/servo/servo/issues/21186). So we got two bugs for the price of one. :)  **/Update**