iOS/MonoVM: waiting doesn't wait

[rolfbjarne]

Description

WaitHandles don't seem to wait.

Repo:

var t = new AutoResetEvent (false);
var rv = t.WaitOne (30000);
Console.WriteLine (rv);

this finishes immediately, printing false.

This happens in the iOS simulator (it does not happen on macOS)

Regression?

Yes, it regressed between 6.0.100-preview.3.21161.23 and 6.0.100-preview.3.21172.2.

CC @CoffeeFlux.

I couldn't figure out the best area label to add to this issue. If you have write-permissions please help me learn by adding exactly one area label.

[CoffeeFlux]

This is likely the result of my threading changes, but just to confirm: this is without AOT? How urgent is the thing this is blocking? Wondering if I should tackle this ASAP or if waiting for next sprint is fine.

[spouliot]

@CoffeeFlux afaik this was seen on bots and those are not AOT, just the JIT. However it might happens on both...

is the thing this is blocking?

We'll not be updating dotnet runtime P3 builds until this is solved. So this blocks any new features (e.g. ICU) from reaching customers for P3.

[jkotas]

If it helps, this is most likely caused by the defines in this file being misconfigured for iOS: https://github.com/dotnet/runtime/blob/main/src/libraries/Native/Unix/System.Native/pal_threading.c#L64

[filipnavara]

Good point, old mono/mono used to manually undef HAVE_CLOCK_MONOTONIC because it was available only on iOS 10+. I thought the minimum iOS version was bumped but not sure to which exact version and whether this was tested on new enough simulator.

[CoffeeFlux]

I assume it's those defines, yeah, but I thought I was careful to get them right for iOS :(

At least now I can test in the simulator without too much trouble, so I'll get something working.

[steveisok]

System.Threading.ThreadPool and System.Threading.Timer suites are routinely crashing. Going to skip them for now. Give them a run once this issue is fixed.