Issue #19873 has been reported by kjtsanaktsidis (KJ Tsanaktsidis). ---------------------------------------- Bug #19873: Thread#native_thread_id is incorrectly cached across fork on Linux https://bugs.ruby-lang.org/issues/19873 * Author: kjtsanaktsidis (KJ Tsanaktsidis) * Status: Open * Priority: Normal * Backport: 3.0: UNKNOWN, 3.1: UNKNOWN, 3.2: UNKNOWN ---------------------------------------- On Linux, when a process forks, the native thread ID of the (only) thread in the forked child should change. ```

...

libc = Fiddle.dlopen(nil) => #<Fiddle::Handle:0x0000ffffb0d8e900> gettid = Fiddle::Function.new(libc['gettid'], [], Fiddle::TYPE_INT) => #<Fiddle::Function:0x0000ffffb15d1130 ... gettid.call => 33 fork { puts gettid.call }; nil; => nil 36

However, the value of `Thread#native_thread_id` is (incorrectly) still set to the old value.

...

Thread.current.native_thread_id => 33 fork { puts Thread.current.native_thread_id }; nil; => nil 33

I think `#native_thread_id` should be re-fetched from the operating system via `gettid(2)` after fork.



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