[ruby-core:113782] [Ruby master Bug#19716] SystemStackError occurs too easily on Alpine Linux (due to small stack size reported by pthread_attr_getstacksize on musl libc)

["alexdowad (Alex Dowad) via ruby-core" <ruby-core@ml.ruby-lang.org>]

Issue #19716 has been reported by alexdowad (Alex Dowad).

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Bug #19716: SystemStackError occurs too easily on Alpine Linux (due to small stack size reported by pthread_attr_getstacksize on musl libc)
https://bugs.ruby-lang.org/issues/19716

* Author: alexdowad (Alex Dowad)
* Status: Open
* Priority: Normal
* ruby -v: ruby 3.1.4p223 (2023-03-30 revision 957bb7cb81) [x86_64-linux-musl]
* Backport: 3.0: UNKNOWN, 3.1: UNKNOWN, 3.2: UNKNOWN
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This is the same problem previously reported against Ruby 2.5 in https://bugs.ruby-lang.org/issues/14387. I just ran into the same problem on Ruby 3.1.4, built on Alpine Linux 3.16.

@hsbt stated in the previous thread (https://bugs.ruby-lang.org/issues/14387#note-28):

> If you have this issue with Ruby 3.2, please file it with another issue.

I hacked `stack_check` in gc.c to print the values of `STACK_START` and `STACK_END` on stack overflow; on the Alpine 3.16 host where this problem just occurred, the values printed were:

> Start=0x7ffd0bf4f000, End=0x7ffd0bf32530

...which shows that Ruby thinks the stack size is only 131072 bytes. On the other hand, `ulimit -s` shows a stack size limit of 8192kb.

This Ruby 3.1.4 was built from unmodified source code downloaded from https://cache.ruby-lang.org; the build was configured using `CFLAGS='-march=native' ./configure --disable-install-doc`.

The invocation of Ruby which blew the stack was `bundle exec rake db:migrate`, on a mid-sized Rails project.

Regarding @ncopa's patch from #14387, @wanabe listed some things which should be done before it is merged into mainline Ruby:

> Okay, The patch needs one or more proofs of its behaviour, like that:
> 
> Original issue [ruby-dev:50421] has gone away.
> Standard test codes run well.
> test-all
> ruby/spec
> getrlimit works on some situations like:
> on single thread
> with multiple threads
> with RLIMIT_STACK environment variable
> getrlimit code of musl is implemented correctly as expected.
> (But It's doubtful whether it can be. I guess that a proof of code soundness is very difficult.)
> Some "real world" applications can work.
> I think it is better example that that application(s) can't work without the patch.

I am happy to help cover some of these points if the Ruby development team is still interested in merging @ncopa's patch.



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