Issue #19154 has been updated by Eregon (Benoit Daloze).
luke-gru (Luke Gruber) wrote in #note-2:
As long as there's a mutex somewhere protecting
these mutations it's safe. There is a mutex around rubygems require. I only had to add
`Ractor.force_shareable!` to 2 or 3 places in the rubygems code and requiring gems now
works across Ractors. I didn't add any tests but I might add some if other people are
interested in this work.
That's completely unsafe. You can look at the implementation of Mutex and you can see
it relies on the GVL. With Ractors there is not a single GVL, so simply said Mutex (and
Monitor too) does not prevent concurrent access with Ractors.
That's one big reason why one cannot share a Mutex/Monitor.
Also sharing a Mutex/Monitor would be a clear violation of the Ractor programming model.
I think `require`/`autoload` in a Ractor should simply be forbidden (raise an exception),
see #17420.
It cannot work since it needs access to $LOADED_FEATURES, and that's owned by the main
Ractor and is unsafe to access for any other Ractor.
----------------------------------------
Bug #19154: Specify require and autoload guarantees in ractors
https://bugs.ruby-lang.org/issues/19154#change-101242
* Author: fxn (Xavier Noria)
* Status: Open
* Priority: Normal
* ruby -v: ruby 3.2.0preview3 (2022-11-27) [x86_64-darwin22]
* Backport: 2.7: UNKNOWN, 3.0: UNKNOWN, 3.1: UNKNOWN
----------------------------------------
Given a file `c.rb`:
```ruby
class C
end
```
the following script:
```ruby
r1 = Ractor.new do
require './c.rb'
end
r2 = Ractor.new do
require './c.rb'
end
r1.take
r2.take
```
raises:
```
% ruby -v foo.rb
ruby 3.2.0preview3 (2022-11-27) [x86_64-darwin22]
foo.rb:1: warning: Ractor is experimental, and the behavior may change in future versions
of Ruby! Also there are many implementation issues.
#<Thread:0x000000010fee2928 run> terminated with exception (report_on_exception is
true):
#<Thread:0x00000001102acfe0 run> terminated with exception (report_on_exception is
true):
<internal:/Users/fxn/.rbenv/versions/3.2.0-preview3/lib/ruby/3.2.0+3/rubygems/core_ext/kernel_require.rb>:164:in
`ensure in require': can not access non-shareable objects in constant
Kernel::RUBYGEMS_ACTIVATION_MONITOR by non-main ractor. (Ractor::IsolationError)
from
<internal:/Users/fxn/.rbenv/versions/3.2.0-preview3/lib/ruby/3.2.0+3/rubygems/core_ext/kernel_require.rb>:167:in
`require'
from foo.rb:6:in `block in <main>'
<internal:/Users/fxn/.rbenv/versions/3.2.0-preview3/lib/ruby/3.2.0+3/rubygems/core_ext/kernel_require.rb>:37:in
`require'<internal:/Users/fxn/.rbenv/versions/3.2.0-preview3/lib/ruby/3.2.0+3/rubygems/core_ext/kernel_require.rb>:164:in
`ensure in require': : can not access non-shareable objects in constant
Kernel::RUBYGEMS_ACTIVATION_MONITOR by non-main ractor. (Ractor::IsolationError)
from
<internal:/Users/fxn/.rbenv/versions/3.2.0-preview3/lib/ruby/3.2.0+3/rubygems/core_ext/kernel_require.rb>:167:in
`require'
can not access non-shareable objects in constant Kernel::RUBYGEMS_ACTIVATION_MONITOR by
non-main ractor. (Ractor::IsolationError) from foo.rb:2:in `block in
<main>'
<internal:/Users/fxn/.rbenv/versions/3.2.0-preview3/lib/ruby/3.2.0+3/rubygems/core_ext/kernel_require.rb>:37:in
`require': can not access non-shareable objects in constant
Kernel::RUBYGEMS_ACTIVATION_MONITOR by non-main ractor. (Ractor::IsolationError)
from foo.rb:2:in `block in <main>'
from foo.rb:6:in `block in <main>'
<internal:ractor>:698:in `take': thrown by remote Ractor. (Ractor::RemoteError)
from foo.rb:9:in `<main>'
<internal:/Users/fxn/.rbenv/versions/3.2.0-preview3/lib/ruby/3.2.0+3/rubygems/core_ext/kernel_require.rb>:164:in
`ensure in require': can not access non-shareable objects in constant
Kernel::RUBYGEMS_ACTIVATION_MONITOR by non-main ractor. (Ractor::IsolationError)
from
<internal:/Users/fxn/.rbenv/versions/3.2.0-preview3/lib/ruby/3.2.0+3/rubygems/core_ext/kernel_require.rb>:167:in
`require'
from foo.rb:2:in `block in <main>'
<internal:/Users/fxn/.rbenv/versions/3.2.0-preview3/lib/ruby/3.2.0+3/rubygems/core_ext/kernel_require.rb>:37:in
`require': can not access non-shareable objects in constant
Kernel::RUBYGEMS_ACTIVATION_MONITOR by non-main ractor. (Ractor::IsolationError)
from foo.rb:2:in `block in <main>'
```
Would it be possible to have documentation about their interaction?
This is important also to understand autoloading within ractors, since constant references
may trigger `require` calls.
--
https://bugs.ruby-lang.org/