[ruby-core:103986] [Ruby master Feature#17849] Fix Timeout.timeout so that it can be used in threaded Web servers

Issue #17849 has been updated by Eregon (Benoit Daloze).


mame (Yusuke Endoh) wrote in #note-14:
> Just FYI. According to @ko1, masking all exceptions in an ensure clause is possible in pure Ruby, as long as you use MRI.

It does not seem to be the case: https://gist.github.com/eregon/9022f5709fa054fc4e488d7de085b254
And I would be surprised if it was on any Ruby, there are two calls there: `handle_interrupt` on `Thread`, and `hash` on `Object`.
Actually such a pattern is a typical pitfall of using `handle_interrupt`, and monitor.rb had such a bug.

The correct pattern is the first one documented here: https://www.rubydoc.info/stdlib/core/Thread.handle_interrupt
Of course that's very verbose and unrealistic to be used for every `ensure`. And additionally it's quite a large overhead when done that way (extra calls, blocks, Hash instances, etc).

In other words, we need VM changes to experiment with this.

I think masking/disabling interrupts in `ensure` and in `finalizers` (https://bugs.ruby-lang.org/issues/13876#change-91365) would be a good improvement, and definitely worth experimenting with.
That won't make `Thread#raise` completely safe indeed, but much more usable, and much safer.
Of course, we will need to evaluate the performance and semantics impact of this change.

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Feature #17849: Fix Timeout.timeout so that it can be used in threaded Web servers
https://bugs.ruby-lang.org/issues/17849#change-92119

* Author: duerst (Martin Dst)
* Status: Open
* Priority: Normal
* Assignee: matz (Yukihiro Matsumoto)
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Making this a separate issue from #17837

Eregon (Benoit Daloze) wrote in https://bugs.ruby-lang.org/issues/17837#note-10 (which is  about timeouts for regular expressions):

> I think fixing Timeout.timeout might be possible.
> The main/major issue is it can trigger within `ensure`, right? Is there anything else?
> We could automatically mask `Thread#raise` within `ensure` so it only happens after the `ensure` body completes.
> And we could still have a larger "hard timeout" if an `ensure` takes way too long (shouldn't happen, but one cannot be sure).
> I recall discussing this with @schneems some time ago on Twitter.





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