February 2026 - ruby-core - ml.ruby-lang.org

[ruby-core:123306] [Ruby Bug#21612] Make sure we never context switch while holding the VM lock
by luke-gru (Luke Gruber) 13 Sep '26

13 Sep '26

Issue #21612 has been reported by luke-gru (Luke Gruber). ---------------------------------------- Bug #21612: Make sure we never context switch while holding the VM lock https://bugs.ruby-lang.org/issues/21612 * Author: luke-gru (Luke Gruber) * Status: Open * Target version: 3.5 * Backport: 3.2: UNKNOWN, 3.3: UNKNOWN, 3.4: UNKNOWN ---------------------------------------- ## The Problem We're seeing errors in our application that uses ractors. The errors look like: ``` [BUG] unexpected situation - recordd:1 current:0 error.c:1097 rb_bug_without_die_internal vm_sync.c:275 disallow_reentry eval_intern.h:136 rb_ec_vm_lock_rec_check eval_intern.h:147 rb_ec_tag_state vm.c:2619 rb_vm_exec vm.c:1702 rb_yield eval.c:1173 rb_ensure ``` We concluded that there was context switching going on while a thread held the VM lock. During the investigation into the issue, we added assertions in the code that we never yield to another thread with the VM lock held. We enabled these VM lock assertions even in single ractor mode. These assertions were failing in a few places, but most notably in finalizers. Finalizers are running with the VM lock held, and they were context switching and causing this issue. ## Why Is This Bad? There are a few reasons we shouldn't be able to context switch while holding the VM lock. In single-ractor mode with threads A and B: 1) Anything in this critical section should be thought of as a transaction related to the memory that's changed inside. if A has the lock, manipulates some global memory and yields to B with the lock still taken and without finishing the memory updates and then B takes it and starts writing to the same memory, the state of this global memory could be corrupted. Currently we don't actually take the VM lock in single-ractor mode, but that doesn't mean these issues can't happen. Yielding to another thread in the middle of manipulating global memory *can* still happen and it causes similar issues. In multi-ractor mode with ractors A and B: 1) We get the same issues as in single-ractor mode. 2) We can also get deadlocks if A has the lock, yields to B and B is blocked waiting on the lock. Unfortunately, many things can cause context switching in Ruby, so what is safe to call when the VM lock is taken? ## Guidelines I've come up with some guidelines. With the VM lock held, You should be able to: * Create ruby objects, call `ruby_xmalloc`, etc. * Jump using `EC_JUMP_TAG`. The lock will automatically be unlocked depending on how far up the call stack you locked it and where you're jumping to. * Check ruby interrupts. Since jumping can pop ruby frames and popping frames checks interrupts, you are allowed. It should never context switch with the VM lock held, even if the ruby thread's quantum is up. You shouldn't be able to: * Call any ruby method or enter Ruby's VM loop. For example, `rb_funcall` is not allowed, nor is `rb_warn` (it can call ruby code). `rb_sprintf` is not allowed because it can call `rb_inspect`. * Call `rb_nogvl` * Enter any blocking operation managed by Ruby. * Call a ruby-level mechanism that can context switch, like `rb_mutex_lock`. ## The Fix Of course, unlocking during finalizers is the main fix but there are other places that also need unlocking. I think adding assertions that the VM lock is not held will be important in finding these bugs and not creating regressions in the future. We don't have to add lots of these, just in a few places. These assertions, which only run in debug mode, should also run when in single-ractor mode. ## Future Work I think some documentation would be helpful for what is and isn't allowed while holding the VM lock and other locks in the cruby source. I am currently working on a `Concurrency Guide` for cruby developers that includes this info. It will not go over every lock, just the VM lock and the "all other locks" category. -- https://bugs.ruby-lang.org/

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[ruby-core:116041] [Ruby master Bug#20155] Using value of rb_fiber_scheduler_current() crashes Ruby
by paddor (Patrik Wenger) 13 Sep '26

13 Sep '26

Issue #20155 has been reported by paddor (Patrik Wenger). ---------------------------------------- Bug #20155: Using value of rb_fiber_scheduler_current() crashes Ruby https://bugs.ruby-lang.org/issues/20155 * Author: paddor (Patrik Wenger) * Status: Open * Priority: Normal * ruby -v: ruby 3.3.0 (2023-12-25 revision 5124f9ac75) [x86_64-linux] * Backport: 3.0: UNKNOWN, 3.1: UNKNOWN, 3.2: UNKNOWN, 3.3: UNKNOWN ---------------------------------------- While trying to manually block/unblock fibers from an extension using the Fiber Scheduler, I noticed that using the return value of `rb_fiber_scheduler_current()` crashes Ruby. I've created a minimal extension gem called "fiber_blocker". Its test suite shows the behavior. See https://github.com/paddor/fiber_blocker, especially the lines containing `FIXME`. Passing `Fiber.scheduler` to the extension functions works. But letting it get the current scheduler itself does not seem to work. Is `rb_fiber_scheduler_current()` not the equivalent to `Fiber.scheduler`? Even just printing the its return value with `#p` will crash Ruby. Ruby either crashes like this: ``` # Running: T1 BEGIN T2 BEGIN T1 END ..T1 BEGIN ext: blocking fiber passed scheduler = #<Scheduler:0x00007fc5f22d39e8 @readable={}, @writable={}, @waiting={}, @closed=false, @lock=#<Thread::Mutex:0x00007fc5f22ec8d0>, @blocking={}, @ready=[], @urgent=[#<IO:fd 5>, #<IO:fd 6>]> T2 BEGIN ext: unblocking fiber T1 END .E Finished in 1.007014s, 3.9721 runs/s, 2.9791 assertions/s. 1) Error: TestFiberBlocker#test_fiber_blocker_current_fiber: fatal: machine stack overflow in critical region No backtrace ``` Or with a segfault: ``` # Running: FiberBlocker.test works. .T1 BEGIN T2 BEGIN T1 END .T1 BEGIN ext: blocking fiber /home/user/dev/oss/async_ruby_test/rbnng/fiber_blocker/test/test_fiber_blocker.rb:40: [BUG] Segmentation fault at 0x00000000390d8f98 ruby 3.3.0 (2023-12-25 revision 5124f9ac75) [x86_64-linux] -- Control frame information ----------------------------------------------- c:0003 p:---- s:0012 e:000011 CFUNC :block_fiber c:0002 p:0014 s:0006 e:000005 BLOCK /home/user/dev/oss/async_ruby_test/rbnng/fiber_blocker/test/test_fiber_blocker.rb:40 [FINISH] c:0001 p:---- s:0003 e:000002 DUMMY [FINISH] -- Ruby level backtrace information ---------------------------------------- /home/user/dev/oss/async_ruby_test/rbnng/fiber_blocker/test/test_fiber_blocker.rb:40:in `block in test_fiber_blocking_in_ext' /home/user/dev/oss/async_ruby_test/rbnng/fiber_blocker/test/test_fiber_blocker.rb:40:in `block_fiber' -- Threading information --------------------------------------------------- Total ractor count: 1 Ruby thread count for this ractor: 4 -- Machine register context ------------------------------------------------ RIP: 0x00007f1554f17ad8 RBP: 0x00000000390d8f90 RSP: 0x00007f153a79e280 RAX: 0x00007f1554addba8 RBX: 0x00007f153a79eab0 RCX: 0x0000000000000000 RDX: 0x00007f1554ade600 RDI: 0x00007f15551e8788 RSI: 0x0000000000000ae1 R8: 0x000000000000002b R9: 0x00007f153a79f038 R10: 0x00007f1554c0b9b0 R11: 0x00007f153a79e490 R12: 0x0000000000000ae1 R13: 0x0000000000000000 R14: 0x0000000000000000 R15: 0x000055ab732d7df0 EFL: 0x0000000000010206 -- C level backtrace information ------------------------------------------- /home/user/.rubies/ruby-3.3.0/lib/libruby.so.3.3(rb_print_backtrace+0x14) [0x7f1554f24961] /home/user/src/ruby-3.3.0/vm_dump.c:820 /home/user/.rubies/ruby-3.3.0/lib/libruby.so.3.3(rb_vm_bugreport) /home/user/src/ruby-3.3.0/vm_dump.c:1151 /home/user/.rubies/ruby-3.3.0/lib/libruby.so.3.3(rb_bug_for_fatal_signal+0x104) [0x7f1554d1c214] /home/user/src/ruby-3.3.0/error.c:1065 /home/user/.rubies/ruby-3.3.0/lib/libruby.so.3.3(sigsegv+0x4f) [0x7f1554e700df] /home/user/src/ruby-3.3.0/signal.c:926 /lib/x86_64-linux-gnu/libc.so.6(0x7f1554842520) [0x7f1554842520] /home/user/.rubies/ruby-3.3.0/lib/libruby.so.3.3(RBASIC_CLASS+0x0) [0x7f1554f17ad8] ./include/ruby/internal/globals.h:178 /home/user/.rubies/ruby-3.3.0/lib/libruby.so.3.3(gccct_method_search) /home/user/src/ruby-3.3.0/vm_eval.c:475 /home/user/.rubies/ruby-3.3.0/lib/libruby.so.3.3(rb_funcallv_scope) /home/user/src/ruby-3.3.0/vm_eval.c:1063 /home/user/.rubies/ruby-3.3.0/lib/libruby.so.3.3(rb_funcallv) /home/user/src/ruby-3.3.0/vm_eval.c:1084 /home/user/.rubies/ruby-3.3.0/lib/libruby.so.3.3(rb_inspect+0x19) [0x7f1554dc1569] /home/user/src/ruby-3.3.0/object.c:697 /home/user/.rubies/ruby-3.3.0/lib/libruby.so.3.3(ruby__sfvextra+0x11a) [0x7f1554e7223a] /home/user/src/ruby-3.3.0/sprintf.c:1119 /home/user/.rubies/ruby-3.3.0/lib/libruby.so.3.3(BSD_vfprintf+0xa69) [0x7f1554e73059] /home/user/src/ruby-3.3.0/vsnprintf.c:830 /home/user/.rubies/ruby-3.3.0/lib/libruby.so.3.3(RBASIC_SET_CLASS_RAW+0x0) [0x7f1554e75b56] /home/user/src/ruby-3.3.0/sprintf.c:1168 /home/user/.rubies/ruby-3.3.0/lib/libruby.so.3.3(ruby_vsprintf0) /home/user/src/ruby-3.3.0/sprintf.c:1169 /home/user/.rubies/ruby-3.3.0/lib/libruby.so.3.3(rb_enc_vsprintf+0x5d) [0x7f1554e75ecd] /home/user/src/ruby-3.3.0/sprintf.c:1195 /home/user/.rubies/ruby-3.3.0/lib/libruby.so.3.3(rb_sprintf+0x9d) [0x7f1554e7607d] /home/user/src/ruby-3.3.0/sprintf.c:1225 /home/user/dev/oss/async_ruby_test/rbnng/fiber_blocker/lib/fiber_blocker/fiber_blocker.so(block_fiber+0x4a) [0x7f1554ad430a] ../../../../ext/fiber_blocker/fiber_blocker.c:29 /home/user/.rubies/ruby-3.3.0/lib/libruby.so.3.3(vm_cfp_consistent_p+0x0) [0x7f1554ef64b4] /home/user/src/ruby-3.3.0/vm_insnhelper.c:3490 /home/user/.rubies/ruby-3.3.0/lib/libruby.so.3.3(vm_call_cfunc_with_frame_) /home/user/src/ruby-3.3.0/vm_insnhelper.c:3492 /home/user/.rubies/ruby-3.3.0/lib/libruby.so.3.3(vm_call_cfunc_with_frame) /home/user/src/ruby-3.3.0/vm_insnhelper.c:3518 /home/user/.rubies/ruby-3.3.0/lib/libruby.so.3.3(vm_call_cfunc_other) /home/user/src/ruby-3.3.0/vm_insnhelper.c:3544 /home/user/.rubies/ruby-3.3.0/lib/libruby.so.3.3(vm_sendish+0x9e) [0x7f1554f06f87] /home/user/src/ruby-3.3.0/vm_insnhelper.c:5581 /home/user/.rubies/ruby-3.3.0/lib/libruby.so.3.3(vm_exec_core) /home/user/src/ruby-3.3.0/insns.def:834 /home/user/.rubies/ruby-3.3.0/lib/libruby.so.3.3(rb_vm_exec+0x19a) [0x7f1554f0d1fa] /home/user/src/ruby-3.3.0/vm.c:2486 /home/user/.rubies/ruby-3.3.0/lib/libruby.so.3.3(rb_vm_invoke_proc+0x5f) [0x7f1554f12e0f] /home/user/src/ruby-3.3.0/vm.c:1728 /home/user/.rubies/ruby-3.3.0/lib/libruby.so.3.3(rb_fiber_start+0x1ba) [0x7f1554cf098a] /home/user/src/ruby-3.3.0/cont.c:2536 /home/user/.rubies/ruby-3.3.0/lib/libruby.so.3.3(fiber_entry+0x20) [0x7f1554cf0d00] /home/user/src/ruby-3.3.0/cont.c:847 /home/user/.rubies/ruby-3.3.0/lib/libruby.so.3.3(rb_threadptr_root_fiber_setup) (null):0 ``` I hope I'm not missing something obvious. My C isn't very good. -- https://bugs.ruby-lang.org/

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[ruby-core:124711] [Ruby Feature#21869] Add receive_all Method to Ractor API for Message Batching
by synacker (Mikhail Milovidov) 12 Sep '26

12 Sep '26

Issue #21869 has been reported by synacker (Mikhail Milovidov). ---------------------------------------- Feature #21869: Add receive_all Method to Ractor API for Message Batching https://bugs.ruby-lang.org/issues/21869 * Author: synacker (Mikhail Milovidov) * Status: Open ---------------------------------------- **Summary** The Ractor API provides an excellent mechanism for inter‑thread communication, but it currently lacks a built‑in message batching technique. I propose adding a receive_all method to enable batch processing of messages, which can significantly improve performance in high‑load scenarios. **Motivation** In distributed queued systems, processing messages one‑by‑one (as with the current receive method) can introduce unnecessary overhead. Batch processing allows: Reduced context‑switching overhead. More efficient I/O operations (e.g., fewer file writes). Better throughput in high‑concurrency environments. **Proposed Solution** Add a receive_all method to the Ractor API that: Returns all available messages in the Ractor’s mailbox at once (as an array). **Demonstration Code** Below is a benchmark comparing individual receive vs. batch receive_all: ``` ruby require 'benchmark' class RactorsTest def initialize(count) @count = count @ractor1 = Ractor.new(count, 'output1.txt') do |count, filename| File.open(filename, 'w') do |file| while count.positive? message = receive file.write("Ractor 1 received message: #{message}\n") file.flush count -= 1 end end end @ractor2 = Ractor.new(count, 'output2.txt') do |count, filename| File.open(filename, 'w') do |file| while count.positive? messages = receive_all messages.each do |message| file.write("Ractor 2 received message: #{message}\n") end count -= messages.length file.flush end end end end def run1 @count.times do |i| @ractor1.send("Message #{i + 1}") end @ractor1.join end def run2 @count.times do |i| @ractor2.send("Message #{i + 1}") end @ractor2.join end end records = 1_000_000 test = RactorsTest.new(records) p [:once, Benchmark.realtime { test.run1 }.round(2)] p [:all, Benchmark.realtime { test.run2 }.round(2)] ``` **Benchmark Results** On my system, receive_all shows ~4x improvement over individual receive: **Key Observations:** Ractor1 (using receive): Processes each message individually, resulting in frequent I/O calls. Ractor2 (using receive_all): Processes all queued messages at once, minimizing I/O overhead -- https://bugs.ruby-lang.org/

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[ruby-core:124851] [Ruby Bug#21918] fiber scheduler: fiber interrupt triggers for IOs that haven't been closed
by chucke (Tiago Cardoso) 12 Sep '26

12 Sep '26

Issue #21918 has been reported by chucke (Tiago Cardoso). ---------------------------------------- Bug #21918: fiber scheduler: fiber interrupt triggers for IOs that haven't been closed https://bugs.ruby-lang.org/issues/21918 * Author: chucke (Tiago Cardoso) * Status: Open * ruby -v: ruby 4.0.0 (2025-12-25 revision 553f1675f3) +PRISM [x86_64-linux] * Backport: 3.2: UNKNOWN, 3.3: UNKNOWN, 3.4: UNKNOWN, 4.0: UNKNOWN ---------------------------------------- I've been chasing an issue, which I believe is to with the recent introduction of the `fiber_interrupt` hook in ruby 4. As a reproduction I have the following snippet: ```ruby require "socket" require_relative "test/fiber/scheduler" # use the one defined here: https://github.com/ruby/ruby/blob/master/test/fiber/scheduler.rb udp = UDPSocket.new(Socket::AF_INET) tcp = Socket.new(Socket::AF_INET, :STREAM, 0) tcp.connect(Socket.sockaddr_in(80, "nghttp2")) t = Thread.start do Thread.current.abort_on_exception = true scheduler = Scheduler.new Fiber.set_scheduler scheduler 5.times do Fiber.schedule do begin puts "#{Fiber.current.object_id} -> wait udp" udp.to_io.wait_readable(2) rescue IOError => e puts "#{Fiber.current.object_id} -> udp io error: #{e}" end begin puts "#{Fiber.current.object_id} -> closing udp" udp.close puts "#{Fiber.current.object_id} -> closed udp" puts "#{Fiber.current.object_id} -> wait tcp" tcp.to_io.wait_readable(2) puts "#{Fiber.current.object_id} -> done" rescue => e puts "#{Fiber.current.object_id} -> tcp io error: #{e}" else puts "#{Fiber.current.object_id} -> closing tcp" tcp.close end end end end t.join ``` This produces the following output to me: ``` 1472 -> wait udp 1488 -> wait udp 1496 -> wait udp 1504 -> wait udp 1512 -> wait udp 1472 -> closing udp 1488 -> closing udp 1488 -> closed udp 1488 -> wait tcp 1496 -> closing udp 1496 -> closed udp 1496 -> wait tcp 1504 -> closing udp 1504 -> closed udp 1504 -> wait tcp 1512 -> closing udp 1512 -> closed udp 1512 -> wait tcp 1512 -> tcp io error: stream closed in another thread 1504 -> tcp io error: stream closed in another thread 1496 -> tcp io error: stream closed in another thread 1488 -> tcp io error: stream closed in another thread 1472 -> closed udp 1472 -> wait tcp 1472 -> done 1472 -> closing tcp ``` The thing that makes this program very confusing is that the "stream closed in another thread" related to the udp socket is raised while waiting for read readiness on the tcp socket. In such a situation, I'd expect the error to relate to the actual socket being waited on, not something else that fiber does not care about anymore. One thing that could have helped would be to have the reference of which IO object the exception relates to in the exception (aka `IOError#io` would return the socket). Nevertheless, I'd still consider an issue that this triggers in the wrong "fiber.yield" moment. Therefore, I think there are two possible outcomes here: 1. all fibers stop on `udp.close` until it is in fact closed (and then IOError is raised before the "closed udp" message can be printed) 2. exceptions related to IOs not actively being monitored by the current fiber are ignored. -- https://bugs.ruby-lang.org/

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[ruby-core:122943] [Ruby Bug#21537] rb_ractor_sched_barrier_start() hangs on Windows
by rhenium (Kazuki Yamaguchi) 09 Sep '26

09 Sep '26

Issue #21537 has been reported by rhenium (Kazuki Yamaguchi). ---------------------------------------- Bug #21537: rb_ractor_sched_barrier_start() hangs on Windows https://bugs.ruby-lang.org/issues/21537 * Author: rhenium (Kazuki Yamaguchi) * Status: Open * ruby -v: ruby 3.5.0dev (2025-08-09T11:32:53Z master 2a6345e957) +PRISM [x64-mswin64_140] * Backport: 3.2: UNKNOWN, 3.3: UNKNOWN, 3.4: UNKNOWN ---------------------------------------- The following script hangs at `GC.start` indefinitely. Pressing Ctrl+C on the terminal interrupts the `sleep` and it appears to resume and prints "in_ractor". ```ruby Ractor.new { sleep 1 GC.start puts "in_ractor" } sleep ``` I also reproduced this with Ruby 3.0.7 from RubyInstaller2. Here is the stack trace with master: ``` 0:006> ~*k 0 Id: 1e88.36c4 Suspend: 1 Teb: 000000c6`92478000 Unfrozen # Child-SP RetAddr Call Site 00 000000c6`929fef18 00007ffa`9e4edf43 ntdll!NtWaitForMultipleObjects+0x14 01 000000c6`929fef20 00007ffa`9e4ede11 KERNELBASE!WaitForMultipleObjectsEx+0x123 02 000000c6`929ff210 00007ff6`756b8164 KERNELBASE!WaitForMultipleObjects+0x11 03 000000c6`929ff250 00007ff6`756b13af miniruby!w32_wait_events+0x108 [C:\w\ruby\thread_win32.c @ 239] 04 000000c6`929ff2d0 00007ff6`756b62a2 miniruby!native_sleep+0xc3 [C:\w\ruby\thread_win32.c @ 360] 05 000000c6`929ff310 00007ff6`75646353 miniruby!sleep_forever+0x82 [C:\w\ruby\thread.c @ 1374] 06 000000c6`929ff350 00007ff6`756e5f4b miniruby!rb_f_sleep+0x53 [C:\w\ruby\process.c @ 4975] 07 000000c6`929ff380 00007ff6`756e5df9 miniruby!vm_call_cfunc_with_frame_+0x14b [C:\w\ruby\vm_insnhelper.c @ 3850] 08 000000c6`929ff460 00007ff6`756e5dbb miniruby!vm_call_cfunc_with_frame+0x29 [C:\w\ruby\vm_insnhelper.c @ 3895] 09 000000c6`929ff4a0 00007ff6`756e5ab7 miniruby!vm_call_cfunc_other+0xc7 [C:\w\ruby\vm_insnhelper.c @ 3922] 0a 000000c6`929ff4e0 00007ff6`756e8363 miniruby!vm_call_cfunc+0x10b [C:\w\ruby\vm_insnhelper.c @ 4003] 0b 000000c6`929ff510 00007ff6`756e7cfe miniruby!vm_call_method_each_type+0x637 [C:\w\ruby\vm_insnhelper.c @ 4827] 0c 000000c6`929ff610 00007ff6`756f39b4 miniruby!vm_call_method+0x152 [C:\w\ruby\vm_insnhelper.c @ 4991] 0d 000000c6`929ff680 00007ff6`756ee003 miniruby!vm_sendish+0x1f4 [C:\w\ruby\vm_insnhelper.c @ 6065] 0e 000000c6`929ff700 00007ff6`756e0f27 miniruby!vm_exec_core+0x25cb [C:\w\ruby\insns.def @ 900] 0f (Inline Function) --------`-------- miniruby!vm_exec_loop+0x8 [C:\w\ruby\vm.c @ 2653] 10 000000c6`929ff860 00007ff6`755b896f miniruby!rb_vm_exec+0x10b [C:\w\ruby\vm.c @ 2624] 11 000000c6`929ff9d0 00007ff6`755baf47 miniruby!rb_ec_exec_node+0x10f [C:\w\ruby\eval.c @ 284] 12 000000c6`929ffb50 00007ff6`75531069 miniruby!ruby_run_node+0x43 [C:\w\ruby\eval.c @ 320] 13 (Inline Function) --------`-------- miniruby!rb_main+0x25 [C:\w\ruby\main.c @ 42] 14 (Inline Function) --------`-------- miniruby!w32_main+0x5f [C:\w\ruby\main.c @ 62] 15 000000c6`929ffb80 00007ff6`7575e3ec miniruby!wmain+0x69 [C:\w\ruby\main.c @ 48] 16 (Inline Function) --------`-------- miniruby!invoke_main+0x22 [D:\a\_work\1\s\src\vctools\crt\vcstartup\src\startup\exe_common.inl @ 90] 17 000000c6`929ffbb0 00007ffa`a03de8d7 miniruby!__scrt_common_main_seh+0x10c [D:\a\_work\1\s\src\vctools\crt\vcstartup\src\startup\exe_common.inl @ 288] 18 000000c6`929ffbf0 00007ffa`a0fdc34c KERNEL32!BaseThreadInitThunk+0x17 19 000000c6`929ffc20 00000000`00000000 ntdll!RtlUserThreadStart+0x2c 1 Id: 1e88.1468 Suspend: 1 Teb: 000000c6`9247a000 Unfrozen # Child-SP RetAddr Call Site 00 000000c6`92dff618 00007ffa`a103259e ntdll!NtWaitForWorkViaWorkerFactory+0x14 01 000000c6`92dff620 00007ffa`a03de8d7 ntdll!TppWorkerThread+0x37e 02 000000c6`92dff980 00007ffa`a0fdc34c KERNEL32!BaseThreadInitThunk+0x17 03 000000c6`92dff9b0 00000000`00000000 ntdll!RtlUserThreadStart+0x2c 2 Id: 1e88.1058 Suspend: 1 Teb: 000000c6`9247c000 Unfrozen # Child-SP RetAddr Call Site 00 000000c6`931ff6a8 00007ffa`a103259e ntdll!NtWaitForWorkViaWorkerFactory+0x14 01 000000c6`931ff6b0 00007ffa`a03de8d7 ntdll!TppWorkerThread+0x37e 02 000000c6`931ffa10 00007ffa`a0fdc34c KERNEL32!BaseThreadInitThunk+0x17 03 000000c6`931ffa40 00000000`00000000 ntdll!RtlUserThreadStart+0x2c 3 Id: 1e88.158c Suspend: 1 Teb: 000000c6`9247e000 Unfrozen # Child-SP RetAddr Call Site 00 000000c6`935ff998 00007ffa`a103259e ntdll!NtWaitForWorkViaWorkerFactory+0x14 01 000000c6`935ff9a0 00007ffa`a03de8d7 ntdll!TppWorkerThread+0x37e 02 000000c6`935ffd00 00007ffa`a0fdc34c KERNEL32!BaseThreadInitThunk+0x17 03 000000c6`935ffd30 00000000`00000000 ntdll!RtlUserThreadStart+0x2c 4 Id: 1e88.3acc Suspend: 1 Teb: 000000c6`92480000 Unfrozen "ruby-timer-thread" # Child-SP RetAddr Call Site 00 000000c6`936ffbc8 00007ffa`9e4ecbbf ntdll!NtWaitForSingleObject+0x14 01 000000c6`936ffbd0 00007ff6`756b7e9d KERNELBASE!WaitForSingleObjectEx+0xaf 02 000000c6`936ffc70 00007ffa`9e0d37b0 miniruby!timer_thread_func+0x45 [C:\w\ruby\thread_win32.c @ 777] 03 000000c6`936ffca0 00007ffa`a03de8d7 ucrtbase!thread_start<unsigned int (__cdecl*)(void *),1>+0x30 04 000000c6`936ffcd0 00007ffa`a0fdc34c KERNEL32!BaseThreadInitThunk+0x17 05 000000c6`936ffd00 00000000`00000000 ntdll!RtlUserThreadStart+0x2c 5 Id: 1e88.2934 Suspend: 1 Teb: 000000c6`92482000 Unfrozen # Child-SP RetAddr Call Site 00 000000c6`937ff4f8 00007ffa`9e4ecbbf ntdll!NtWaitForSingleObject+0x14 01 000000c6`937ff500 00007ff6`756b1276 KERNELBASE!WaitForSingleObjectEx+0xaf 02 000000c6`937ff5a0 00007ff6`756f7f47 miniruby!native_cond_timedwait_ms+0x62 [C:\w\ruby\thread_win32.c @ 483] 03 (Inline Function) --------`-------- miniruby!vm_cond_wait+0x28 [C:\w\ruby\vm_sync.c @ 211] 04 000000c6`937ff5f0 00007ff6`756b2c83 miniruby!rb_vm_cond_wait+0x37 [C:\w\ruby\vm_sync.c @ 220] 05 000000c6`937ff620 00007ff6`756f7f02 miniruby!rb_ractor_sched_barrier_start+0x67 [C:\w\ruby\thread_win32.c @ 956] 06 000000c6`937ff650 00007ff6`755c7a78 miniruby!rb_vm_barrier+0x1e [C:\w\ruby\vm_sync.c @ 265] 07 (Inline Function) --------`-------- miniruby!rb_gc_vm_barrier+0x5 [C:\w\ruby\gc.c @ 179] 08 (Inline Function) --------`-------- miniruby!gc_enter+0x25 [C:\w\ruby\gc\default\default.c @ 6609] 09 000000c6`937ff680 00007ff6`755c442e miniruby!gc_start+0xc0 [C:\w\ruby\gc\default\default.c @ 6334] 0a 000000c6`937ff6e0 00007ff6`755cdd0f miniruby!garbage_collect+0x42 [C:\w\ruby\gc\default\default.c @ 6316] 0b 000000c6`937ff710 00007ff6`755c2cc3 miniruby!rb_gc_impl_start+0x4b [C:\w\ruby\gc\default\default.c @ 6767] 0c 000000c6`937ff740 00007ff6`756d5c7b miniruby!gc_start_internal+0x4f [C:\w\ruby\gc.c @ 3447] 0d 000000c6`937ff780 00007ff6`756ee237 miniruby!builtin_invoker4+0x23 [C:\w\ruby\vm_insnhelper.c @ 7373] 0e (Inline Function) --------`-------- miniruby!invoke_bf+0x32 [C:\w\ruby\vm_insnhelper.c @ 7485] 0f (Inline Function) --------`-------- miniruby!vm_invoke_builtin+0x32 [C:\w\ruby\vm_insnhelper.c @ 7493] 10 000000c6`937ff7c0 00007ff6`756e0f27 miniruby!vm_exec_core+0x27ff [C:\w\ruby\build-debug\vm.inc @ 4621] 11 (Inline Function) --------`-------- miniruby!vm_exec_loop+0x8 [C:\w\ruby\vm.c @ 2653] 12 000000c6`937ff920 00007ff6`756f08b0 miniruby!rb_vm_exec+0x10b [C:\w\ruby\vm.c @ 2624] 13 (Inline Function) --------`-------- miniruby!invoke_iseq_block_from_c+0x1e3 [C:\w\ruby\vm.c @ 1651] 14 (Inline Function) --------`-------- miniruby!invoke_block_from_c_proc+0x2f2 [C:\w\ruby\vm.c @ 1745] 15 000000c6`937ffa90 00007ff6`756b6bf9 miniruby!vm_invoke_proc+0x324 [C:\w\ruby\vm.c @ 1775] 16 000000c6`937ffbd0 00007ff6`756b7987 miniruby!thread_do_start_proc+0x131 [C:\w\ruby\thread.c @ 584] 17 (Inline Function) --------`-------- miniruby!thread_do_start+0x37 [C:\w\ruby\thread.c @ 626] 18 000000c6`937ffc40 00007ff6`756b7720 miniruby!thread_start_func_2+0x243 [C:\w\ruby\thread.c @ 677] 19 000000c6`937ffe90 00007ffa`9e0d37b0 miniruby!thread_start_func_1+0x74 [C:\w\ruby\thread_win32.c @ 659] 1a 000000c6`937ffec0 00007ffa`a03de8d7 ucrtbase!thread_start<unsigned int (__cdecl*)(void *),1>+0x30 1b 000000c6`937ffef0 00007ffa`a0fdc34c KERNEL32!BaseThreadInitThunk+0x17 1c 000000c6`937fff20 00000000`00000000 ntdll!RtlUserThreadStart+0x2c # 6 Id: 1e88.4f4 Suspend: 1 Teb: 000000c6`92486000 Unfrozen # Child-SP RetAddr Call Site 00 000000c6`93bff768 00007ffa`a10d793e ntdll!DbgBreakPoint 01 000000c6`93bff770 00007ffa`a03de8d7 ntdll!DbgUiRemoteBreakin+0x4e 02 000000c6`93bff7a0 00007ffa`a0fdc34c KERNEL32!BaseThreadInitThunk+0x17 03 000000c6`93bff7d0 00000000`00000000 ntdll!RtlUserThreadStart+0x2c ``` -- https://bugs.ruby-lang.org/

3 2

[ruby-core:121450] [Ruby Bug#21200] Ractor spuriously hangs, segfault or errors
by Eregon (Benoit Daloze) 08 Sep '26

08 Sep '26

Issue #21200 has been reported by Eregon (Benoit Daloze). ---------------------------------------- Bug #21200: Ractor spuriously hangs, segfault or errors https://bugs.ruby-lang.org/issues/21200 * Author: Eregon (Benoit Daloze) * Status: Open * Assignee: ractor * Backport: 3.1: UNKNOWN, 3.2: UNKNOWN, 3.3: UNKNOWN, 3.4: UNKNOWN ---------------------------------------- For a new test `test_ractor_parallel` I added in https://github.com/ruby/etc/pull/52/files This seems a Ractor bug. Example failures: https://github.com/ruby/ruby/actions/runs/14097239052/job/39486770259?pr=12… ``` 1) Failure: TestEtc#test_ractor_parallel [/Users/runner/work/ruby/ruby/src/test/etc/test_etc.rb:178]: assert_separately failed with error message pid 51588 exit 0 | [BUG] ``` https://github.com/ruby/ruby/actions/runs/14094646363/job/39479353266?pr=12… ``` TestEtc#test_ractor_parallel [/Users/runner/work/ruby/ruby/src/test/etc/test_etc.rb:178]: assert_separately failed with error message pid 47346 exit 0 | [BUG] pthread_mutex_lock: Invalid argument (EINVAL) | ruby 3.5.0dev (2025-03-26T22:25:25Z pull/12984/merge 1ea32181b7) +PRISM [arm64-darwin23] | | -- Crash Report log information -------------------------------------------- | See Crash Report log file in one of the following locations: | * ~/Library/Logs/DiagnosticReports | * /Library/Logs/DiagnosticReports | for more details. | Don't forget to include the above Crash Report log file in bug reports. | | -- Control frame information ----------------------------------------------- | | | -- Threading information --------------------------------------------------- | Total ractor count: 1 | Ruby thread count for this ractor: 0 | | -- C level backtrace information ------------------------------------------- | [BUG] Segmentation fault at 0xfffffffffffffff8 | ruby 3.5.0dev (2025-03-26T22:25:25Z pull/12984/merge 1ea32181b7) +PRISM [arm64-darwin23] | | -- Crash Report log information -------------------------------------------- | See Crash Report log file in one of the following locations: | * ~/Library/Logs/DiagnosticReports | * /Library/Logs/DiagnosticReports | for more details. | Don't forget to include the above Crash Report log file in bug reports. | | Crashed while printing bug report | [IMPORTANT] | Don't forget to include the Crash Report log file under | DiagnosticReports directory in bug reports. | ``` https://github.com/ruby/ruby/actions/runs/14069270994/job/39402894235#step:… ``` 1) Error: TestEtc#test_ractor_parallel: Test::Unit::ProxyError: execution of Test::Unit::CoreAssertions#assert_separately expired timeout (10 sec) pid 145797 killed by SIGKILL (signal 9) | /home/runner/work/ruby/ruby/src/test/etc/test_etc.rb:178:in 'TestEtc#test_ractor_parallel' ``` The test has been disabled for now in https://github.com/ruby/ruby/pull/12992. -- https://bugs.ruby-lang.org/

2 1

[ruby-core:111960] [Ruby master Bug#19364] Issue with tracepoint enable/disable across ractors
by luke-gru (Luke Gruber) 08 Sep '26

08 Sep '26

Issue #19364 has been reported by luke-gru (Luke Gruber). ---------------------------------------- Bug #19364: Issue with tracepoint enable/disable across ractors https://bugs.ruby-lang.org/issues/19364 * Author: luke-gru (Luke Gruber) * Status: Open * Priority: Normal * Backport: 2.7: UNKNOWN, 3.0: UNKNOWN, 3.1: UNKNOWN, 3.2: UNKNOWN ---------------------------------------- This sometimes segfaults: ```ruby def test_enable_disable_in_multiple_ractors_with_target rs = [] 100.times do |i| # setup new iseqs Kernel.define_method :"my_method_to_change_for_tracing_#{i}" do true end end 100.times do |i| rs << Ractor.new(i) do |j| meth = :"my_method_to_change_for_tracing_#{j}" tp = TracePoint.new(:line) { } # local to ractor 100.times do tp.enable(target: method(meth)) # change iseq internals of given method, should be done with lock tp.disable # disable hooks should hold lock too, changes method definition internals end end end rs.each(&:take) # shouldn't raise end test_enable_disable_in_multiple_ractors_with_target() ``` Changing iseq internals is done without the VM lock. This is true in Tracepoint#enable and Tracepoint#disable methods. I have a patch coming. -- https://bugs.ruby-lang.org/

3 2

[ruby-core:116061] [Ruby master Bug#20158] Ractor affects Coverage results
by janosch-x 08 Sep '26

08 Sep '26

Issue #20158 has been reported by janosch-x (Janosch Müller). ---------------------------------------- Bug #20158: Ractor affects Coverage results https://bugs.ruby-lang.org/issues/20158 * Author: janosch-x (Janosch Müller) * Status: Open * Priority: Normal * ruby -v: ruby 3.3.0preview1 (2023-05-12 master a1b01e7701) [arm64-darwin22] * Backport: 3.0: UNKNOWN, 3.1: UNKNOWN, 3.2: UNKNOWN, 3.3: UNKNOWN ---------------------------------------- I have a large rspec test suite. I found that if I call a Ractor, the Coverage results are strongly affected, i.e. almost all files appear to be uncovered. This happens even if I only ever call a Ractor before the library or rspec are required. Unfortunately, I was not able to build a simple repro yet. I assume it is a timing thing and only affects larger suites, or it only happens if there are multiple files, and maybe if the library lazily requires its sub-modules? However, I guess this should produce the same results when added to the spec_helper.rb of other large suites: ```ruby # Ractor.new { nil } # uncomment this to affect coverage results require 'coverage' Coverage.start # require library, set up rspec etc. RSpec.configuration.after(:suite) do # this number is greatly reduced and unstable when calling Ractor above p Coverage.result.values.sum { |arr| arr.sum(&:to_i) } end ``` I had this problem in [this library](https://github.com/jaynetics/character_set/). The problem affects simplecov users as well, as described [here](https://github.com/simplecov-ruby/simplecov/issues/1058). -- https://bugs.ruby-lang.org/

4 5

[ruby-core:121941] [Ruby Bug#21315] Finalizers violate the `rb_ractor_confirm_belonging` assertion
by byroot (Jean Boussier) 08 Sep '26

08 Sep '26

Issue #21315 has been reported by byroot (Jean Boussier). ---------------------------------------- Bug #21315: Finalizers violate the `rb_ractor_confirm_belonging` assertion https://bugs.ruby-lang.org/issues/21315 * Author: byroot (Jean Boussier) * Status: Open * Assignee: ractor * Backport: 3.2: UNKNOWN, 3.3: UNKNOWN, 3.4: UNKNOWN ---------------------------------------- Reproduction (with assertions enabled): ```ruby require "tempfile" Ractor.new do 10.times do Tempfile.new end end.take GC.start ``` ``` <OBJ_INFO:rb_ractor_confirm_belonging@../src/ractor_core.h:375> (File) /home/runner/work/ruby/ruby/src/lib/tempfile.rb:387: [BUG] rb_ractor_confirm_belonging object-ractor id:1, current-ractor id:2 ruby 3.5.0dev (2025-05-09T15:51:24Z pull/13291/merge e289a1dc58) +PRISM [x86_64-linux] -- Control frame information ----------------------------------------------- c:0005 p:0007 s:0025 e:000024 METHOD /home/runner/work/ruby/ruby/src/lib/tempfile.rb:387 [FINISH] c:0004 p:0022 s:0020 e:000019 METHOD /home/runner/work/ruby/ruby/src/lib/prism/parse_result.rb:833 [FINISH] c:0003 p:---- s:0012 e:000011 CFUNC :parse_lex_file c:0002 p:0006 s:0007 e:000006 BLOCK /home/runner/work/ruby/ruby/src/test/prism/ractor_test.rb:26 [FINISH] c:0001 p:---- s:0003 e:000002 DUMMY [FINISH] -- Ruby level backtrace information ---------------------------------------- /home/runner/work/ruby/ruby/src/test/prism/ractor_test.rb:26:in 'block in test_parse_lex_file' /home/runner/work/ruby/ruby/src/test/prism/ractor_test.rb:26:in 'parse_lex_file' /home/runner/work/ruby/ruby/src/lib/prism/parse_result.rb:833:in 'initialize' /home/runner/work/ruby/ruby/src/lib/tempfile.rb:387:in 'call' -- Threading information --------------------------------------------------- Total ractor count: 2 Ruby thread count for this ractor: 1 -- C level backtrace information ------------------------------------------- /home/runner/work/ruby/ruby/build/ruby(rb_print_backtrace+0x14) [0x561441aeedbf] ../src/vm_dump.c:843 /home/runner/work/ruby/ruby/build/ruby(rb_vm_bugreport) ../src/vm_dump.c:1175 /home/runner/work/ruby/ruby/build/ruby(bug_report_end+0x0) [0x561441aa3f39] ../src/error.c:1097 /home/runner/work/ruby/ruby/build/ruby(rb_bug_without_die_internal) ../src/error.c:1097 /home/runner/work/ruby/ruby/build/ruby(die+0x0) [0x5614416e237f] ../src/error.c:1115 /home/runner/work/ruby/ruby/build/ruby(rb_bug) ../src/error.c:1117 /home/runner/work/ruby/ruby/build/ruby(rb_ractor_confirm_belonging+0xde) [0x56144188c6be] ../src/ractor_core.h:376 /home/runner/work/ruby/ruby/build/ruby(vm_exec_core+0xef) [0x5614418b23ef] /home/runner/work/ruby/ruby/build/vm.inc:2500 /home/runner/work/ruby/ruby/build/ruby(rb_vm_exec+0x156) [0x5614418a4676] ../src/vm.c:2618 /home/runner/work/ruby/ruby/build/ruby(vm_call0_cc+0x13d) [0x5614418aa1dd] ../src/vm_eval.c:101 /home/runner/work/ruby/ruby/build/ruby(rb_vm_call0+0x4c) [0x5614418b1cc5] ../src/vm_eval.c:61 /home/runner/work/ruby/ruby/build/ruby(rb_vm_call_kw) ../src/vm_eval.c:326 /home/runner/work/ruby/ruby/build/ruby(rb_check_funcall_default_kw) ../src/vm_eval.c:694 /home/runner/work/ruby/ruby/build/ruby(rb_gc_run_obj_finalizer+0x1cf) [0x56144170220f] ../src/gc.c:306 /home/runner/work/ruby/ruby/build/ruby(rb_multi_ractor_p+0x0) [0x56144170246f] ../src/gc/default/default.c:2820 /home/runner/work/ruby/ruby/build/ruby(rb_vm_lock_enter) ../src/vm_sync.h:74 /home/runner/work/ruby/ruby/build/ruby(rb_gc_vm_lock) ../src/gc.c:137 /home/runner/work/ruby/ruby/build/ruby(finalize_list) ../src/gc/default/default.c:2843 /home/runner/work/ruby/ruby/build/ruby(finalize_deferred_heap_pages) ../src/gc/default/default.c:2866 ``` I think it wouldn't be hard to disable that check when running a finalizer, but I don't know if it's the correct thing to do. -- https://bugs.ruby-lang.org/

5 8

[ruby-core:112091] [Ruby master Bug#19387] Issue with ObjectSpace.each_objects not returning IO objects after starting a ractor
by luke-gru (Luke Gruber) 08 Sep '26

08 Sep '26

Issue #19387 has been reported by luke-gru (Luke Gruber). ---------------------------------------- Bug #19387: Issue with ObjectSpace.each_objects not returning IO objects after starting a ractor https://bugs.ruby-lang.org/issues/19387 * Author: luke-gru (Luke Gruber) * Status: Open * Priority: Normal * Backport: 2.7: UNKNOWN, 3.0: UNKNOWN, 3.1: UNKNOWN, 3.2: UNKNOWN ---------------------------------------- ```ruby r = Ractor.new do receive # block, the problem is not the termination of the ractor but the starting end ObjectSpace.each_object(IO) { |io| p io # we get no objects } ``` -- https://bugs.ruby-lang.org/

6 9