[#100309] How to use backport custom field — Jun Aruga <jaruga@...>
Please allow my ignorance.
9 messages
2020/10/06
[#100310] Re: How to use backport custom field
— "NARUSE, Yui" <naruse@...>
2020/10/06
IkJhY2twb3J0IGN1c3RvbSBmaWVsZCIgaXMgb25seSBhdmFpbGFibGUgZm9yIHRpY2tldHMgd2hv
[#100311] Re: How to use backport custom field
— Jun Aruga <jaruga@...>
2020/10/06
On Tue, Oct 6, 2020 at 4:44 PM NARUSE, Yui <[email protected]> wrote:
[#100314] Re: How to use backport custom field
— "NARUSE, Yui" <naruse@...>
2020/10/06
VGhhbmsgeW91IGZvciBjb25maXJtYXRpb24uCkkgY2hlY2tlZCBhZ2FpbiBhbmQgdG8gZWRpdCBi
[#100322] Re: How to use backport custom field
— Jun Aruga <jaruga@...>
2020/10/07
On Tue, Oct 6, 2020 at 7:25 PM NARUSE, Yui <[email protected]> wrote:
[#100326] Re: How to use backport custom field
— "NARUSE, Yui" <naruse@...>
2020/10/07
SSBhZGRlZCB5b3UgdG8gIlJlcG9ydGVyIiByb2xlIGluIHRoZSBwcm9qZWN0CgoyMDIw5bm0MTDm
[#100327] Re: How to use backport custom field
— Jun Aruga <jaruga@...>
2020/10/07
On Wed, Oct 7, 2020 at 1:42 PM NARUSE, Yui <[email protected]> wrote:
[ruby-core:100476] [Ruby master Feature#17274] Ractor.make_shareable(obj)
From:
eregontp@...
Date:
2020-10-21 18:47:00 UTC
List:
ruby-core #100476
Issue #17274 has been updated by Eregon (Benoit Daloze).
@ko1 What's the difference with `Object#deep_freeze(skip_shareable: false)` from #17145 ?
----------------------------------------
Feature #17274: Ractor.make_shareable(obj)
https://bugs.ruby-lang.org/issues/17274#change-88097
* Author: ko1 (Koichi Sasada)
* Status: Open
* Priority: Normal
----------------------------------------
This ticket describes the semantics of "shareable" and proposes a new method `Ractor.make_shareable(obj)`.
With this method, `obj` becomes a shareable object by freezing it and reachable objects if it is necessary and it is possible.
## Background
"Shareable object" is new term used by Ractors.
* (1) We can send a reference to send a shareable object instead of doing deep copy.
* (2) We can access to a constant which contains a shareable object from non-main ractors.
(1) is (mainly) performance and (2) is programmability (how to rewrite the libraries and so on). See [Feature #1727] for the examples of (2).
The definition of shareable object is thread-safe, ractor-safe object, they are safe to access from multiple ractors simultaneously.
The following conditions are definition of "shareable object" (`obj` is shareable object if ...).
* SPECIAL_CONST objects are shareable (also be frozen).
* if `RBASIC(obj)->flags | FL_SHAREABLE` is true, it is shareable.
* T_OBJECT: if all instance variables only refer to shareable objects (def1) and itself is frozen (def2)
* T_ARRAY: (def1) + (def2) + if all elements are shareable objects
* T_HASH: (def1) + (def2) + if all keys and values are sharable objects and default_proc/value (IFNONE, in C-level) is a sharable object
* T_STRUCT: (def1) + (def2) + if all members are shareable objects
* T_RATIONAL: (def1) + (def2) + if num/den are shareaable
* T_COMPLEXL: (def1) + (def2) + if imag/real are shareable
* T_STRING, T_FILE, T_MATCH, T_REGEXP: (def1) + (def2)
`T_DATA` (user customizable data structure) is difficult problem because if it is frozen, it can modify a state (== we can use (def2)), for example current Queue implementation ignores frozen flag. So we define the semantics like:
* `T_DATA`: (def1) + if `RTYPEDDATA_P(obj)` is true and `rb_data_type_t::flags | RUBY_TYPED_FROZEN_SHAREABLE`, we rely on (def2). Otherwize, this T_DATA object can not become a shareable object. Also we need to check reachable objects are shareable.
`Ractor.shareable?(obj)` checks this definitions.
Note that you can add `FL_SHAREABLE` flag to any objects, so if you know there is no mutation or enough protected, you can set the flag and it will be a shareable object. For example, [Feature #17261] use this flag and `TVar`s are shareable objects.
## Proposal
As you can see, most of objects are shareable if they are frozen and they are only refers shareable/frozen objects.
`Ractor.make_shareable(obj)` tries to freeze objects recursively if it is non-shareable objects.
```ruby
# puseudo-code
def Ractor.make_shareable(obj)
return obj if Ractor.shareable(obj)
obj.freeze
if obj.is T_DATA and (obj.type.flags | RUBY_TYPED_FROZEN_SHAREABLE) == 0
raise "can not make shareable object for ..."
end
obj.reachable_objects{|o|
Ractor.make_shareable(o)
}
# only refer to the shareable objects, so it can be a shareable.
obj.set! FL_SHAREBLE
end
```
If it raises an error in the middle of the process, half-baked state are remained.
```
begin
Ractor.make_shareable [ a1 = [1, 2],
Thread.new{},
a2 = [3, 4]]
rescue Ractor::Error
end
p Ractor.shareable?(a1) #=> true
p Ractor.shareable?(a2) #=> false
```
## Implementation
https://github.com/ruby/ruby/pull/3678
and it was already merged to propose https://bugs.ruby-lang.org/issues/17273
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