Issue #19315 has been updated by himura467 (Akito Shitara). byroot (Jean Boussier) wrote in #note-48:
as it's a new contention point for Ractors, and if the main thread fork while a background ractor is holding this lock, the child will likely end up deadlocking at some point.
That's a valid concern. However, it might be structurally addressable via internal synchronization, similar to how jemalloc manages its internal states for concurrency. Ref: https://github.com/jemalloc/jemalloc/blob/dev/src/jemalloc_fork.c That said, doing so would add implementation complexity. Given that code combining Ractors with `RSTRING_PTR()` expecting NUL termination might not be very common yet, it is worth discussing how much effort we should put into handling this specific case. byroot (Jean Boussier) wrote in #note-48:
But I can't say I like that solution
To be honest, I can't say I like that solution either, so I'm trying to think if there might be a better approach to implement this. ---------------------------------------- Feature #19315: Lazy substrings in CRuby https://bugs.ruby-lang.org/issues/19315#change-117628 * Author: Eregon (Benoit Daloze) * Status: Open ---------------------------------------- CRuby should implement lazy substrings, i.e., "abcdef"[1..3] must not copy bytes. Currently CRuby only reuse the char* if the substring is until the end of the buffer. But it should also work wherever the substring starts and ends. Yes, it means RSTRING_PTR() might need to allocate to \0-terminate, so be it, it's worth it. There is already code for this (`SHARABLE_MIDDLE_SUBSTRING`), but it's disabled by default and `RSTRING_PTR()` needs to be changed to deal with this. It seems a good idea to introduce a variant of `RSTRING_PTR` which doesn't guarantee \0-termination, so such callers can then use the existing bytes always without copy. There are countless workarounds for this missing optimization, all not worth it with lazy substring and all less readable: * https://bugs.ruby-lang.org/issues/19314 * https://bugs.ruby-lang.org/issues/18598#note-3 * https://github.com/ruby/net-protocol/pull/14 * Manual lazy substrings which track string + index + length * More but I don't remember all now, feel free to comment or link more urls/tickets. -- https://bugs.ruby-lang.org/