Porting tokio to redox - update 2

content/news/rsoc-porting-tokio-to-redox.md → content/news/rsoc-porting-tokio-1.md

 +++
-title = "RSoC: Porting tokio to redox"
+title = "RSoC: Porting tokio to redox - week 1"
 author = "jD91mZM2"
 date = "2018-05-21T19:03:54+02:00"
 +++
@@ -68,6 +68,6 @@ and I was back to where I left off Day 3, but now with *much* better - and faste
 Now, what was the answer to why `tokio::spawn` wasn't working?
 Oh that was simple, my VM only has one CPU and it turns out tokio adjusts the number of worker threads
 to the amount of CPUs.
-I mean, it probably should be work anyway. Guessing that could be a tokio bug.
+I mean, it probably should work anyway. Guessing that could be a tokio bug.
 For now I just made it use at least two workers.
 This and a few other problems were patched, and here we are.

content/news/rsoc-porting-tokio-2.md

++++
+title = "RSoC: Porting tokio to redox - week 2"
+author = "jD91mZM2"
+date = "2018-05-30T12:27:25+02:00"
++++
+
+# Porting tokio, update 2
+
+I honestly never thought I'd be back with another post.
+Almost all tokio examples worked, what else was there to do?
+So I stopped writing daily updates to later compile to one summary (like this one), and went on with my life.
+But programs have strange habits of breaking.
+
+Immediately after my last blog I was asked to try and port hyper.
+With a few modifications, it worked!
+Then I was asked to port reqwest, and that's where things started breaking.
+Apparently the hyper I ported was a pre-release, meanwhile reqwest still used hyper 0.11.9.
+And hyper 0.11.9 still used tokio-core.
+You would've thought this was the end of it. "Too old tokio, can't continue".
+But luckily I happened to have read somewhere that tokio-core is now a wrapper interface around the new tokio
+so that old programs still work!
+
+Unlike hyper, reqwest didn't work out of the box. It received EOF too early when reading.
+I was almost an hour in when I remembered that I got the same issue earlier!
+Apparently tokio-core is not just a wrapper - it has some sort of copies of the tokio code.
+What this means is that my old fixes to tokio were not available in tokio-core, so I had to backport those.
+
+Reqwest worked, but during larger transactions it still received EOF too early... randomly.
+And it sometimes worked. And it sometimes only worked when I added debug prints...
+After a few hours of nonstop cursing at my computer I noticed that because of redox's level-triggering model it
+received old events and treated them as new, meaning one readable event could result in two reads,
+where the second one reads 0 bytes - which is treated as EOF.
+This was fixed by simply clearing another value as well when clearing readiness.
+
+The was still one last issue. Remember the `tokio::spawn` issue from the last blog?
+Tokio failed to do multiple things simultaneously.
+Last time I fixed that by increasing the number of workers, quickly dismissing it as a tokio bug.
+Only one problem: tokio-core doesn't have a threadpool.
+I really like this issue actually, it made me go back to an old issue and solve it properly :)
+The fix was easy too, I suddenly remembered that calling `accept()` on a non-blocking listener on redox was blocking anyway.
+And looking back at tokio's accept code I noticed that I simply forgot to clear readiness (since redox's event model is level-triggering).
+
+## Rounding up
+
+I was really annoyed by the impossible-to-debug random early EOF issue.
+But I REALLY liked that the `tokio::spawn` issue wasn't upstream,
+so I could go back and solve it properly myself.
+
+One sad thing is that almost all code I wrote will be able to be reverted once
+redox changes to an edge-triggering model instead,
+[which they most likely will](https://github.com/redox-os/netstack/issues/27).
+
+I've send pull requests to both [pkgutils](https://github.com/redox-os/pkgutils/pull/28) and [netutils](https://github.com/redox-os/netutils/pull/33)
+that replaces the outdated hyper with the latest version of reqwest.
+
+I didn't expect to have to go back to my patched tokio code, but I'm happy I did :)