[ruby-core:115911] [Ruby master Bug#20089] Fiber#kill transfers to root fiber
Issue #20089 has been reported by rmosolgo (Robert Mosolgo). ---------------------------------------- Bug #20089: Fiber#kill transfers to root fiber https://bugs.ruby-lang.org/issues/20089 * Author: rmosolgo (Robert Mosolgo) * Status: Open * Priority: Normal * ruby -v: ruby 3.3.0 (2023-12-25 revision 5124f9ac75) [x86_64-darwin22] * Backport: 3.0: UNKNOWN, 3.1: UNKNOWN, 3.2: UNKNOWN, 3.3: UNKNOWN ---------------------------------------- I was hoping to use `Fiber#kill` to clean up formerly `.transfer`-d Fibers and work around https://bugs.ruby-lang.org/issues/20081, but I found that `Fiber#kill` has a similar control flow jump behavior. Is this on purpose, or a bug? Here's a script to test the behavior: ```ruby manager = Fiber.new do worker = Fiber.new do puts "2. Begin Worker" manager.transfer puts "This should never print -- killed" end puts "1. Transfer to Worker" worker.transfer puts "3. Killing Worker" worker.kill puts "4. Finished manager" end manager.transfer puts "5. Finished script" ``` I expected items `1` through `5` to be printed in order, but in fact, `4` is never printed: ``` $ ruby fiber_transfer_test.rb 1. Transfer to Worker 2. Begin Worker 3. Killing Worker 5. Finished script ``` It seems like `worker.kill` is transferring control to the top-level fiber instead of giving it back to `manager`. I also tried having the thread kill _itself_, hoping it would return to the fiber that originally `.transfer`ed to it, but it also seems to jump out: ```ruby manager = Fiber.new do worker = Fiber.new do puts "2. Begin Worker" manager.transfer Fiber.current.kill puts "This should never print -- killed" end puts "1. Transfer to Worker" worker.transfer puts "3. Killing Worker" worker.transfer puts "4. Finished manager" end manager.transfer puts "5. Finished script" ``` Prints: ``` 1. Transfer to Worker 2. Begin Worker 3. Killing Worker 5. Finished script ``` -- https://bugs.ruby-lang.org/
Issue #20089 has been updated by ioquatix (Samuel Williams). Transfer is uni-directional and keeps no state about the caller. It's up to the caller to implement its own control flow if preferred. It's a low level operation which must be used more carefully. ```ruby manager = Fiber.new do worker = Fiber.new do puts "2. Begin Worker" manager.transfer Fiber.current.kill puts "This should never print -- killed" ensure manager.transfer end puts "1. Transfer to Worker" worker.transfer puts "3. Killing Worker" worker.transfer puts "4. Finished manager" end manager.transfer puts "5. Finished script" ``` By explicitly adding the flow control, we can achieve your desired output. Hope this helps. ---------------------------------------- Bug #20089: Fiber#kill transfers to root fiber https://bugs.ruby-lang.org/issues/20089#change-105895 * Author: rmosolgo (Robert Mosolgo) * Status: Open * Priority: Normal * ruby -v: ruby 3.3.0 (2023-12-25 revision 5124f9ac75) [x86_64-darwin22] * Backport: 3.0: UNKNOWN, 3.1: UNKNOWN, 3.2: UNKNOWN, 3.3: UNKNOWN ---------------------------------------- I was hoping to use `Fiber#kill` to clean up formerly `.transfer`-d Fibers and work around https://bugs.ruby-lang.org/issues/20081, but I found that `Fiber#kill` has a similar control flow jump behavior. Is this on purpose, or a bug? Here's a script to test the behavior: ```ruby manager = Fiber.new do worker = Fiber.new do puts "2. Begin Worker" manager.transfer puts "This should never print -- killed" end puts "1. Transfer to Worker" worker.transfer puts "3. Killing Worker" worker.kill puts "4. Finished manager" end manager.transfer puts "5. Finished script" ``` I expected items `1` through `5` to be printed in order, but in fact, `4` is never printed: ``` $ ruby fiber_transfer_test.rb 1. Transfer to Worker 2. Begin Worker 3. Killing Worker 5. Finished script ``` It seems like `worker.kill` is transferring control to the top-level fiber instead of giving it back to `manager`. I also tried having the thread kill _itself_, hoping it would return to the fiber that originally `.transfer`ed to it, but it also seems to jump out: ```ruby manager = Fiber.new do worker = Fiber.new do puts "2. Begin Worker" manager.transfer Fiber.current.kill puts "This should never print -- killed" end puts "1. Transfer to Worker" worker.transfer puts "3. Killing Worker" worker.transfer puts "4. Finished manager" end manager.transfer puts "5. Finished script" ``` Prints: ``` 1. Transfer to Worker 2. Begin Worker 3. Killing Worker 5. Finished script ``` -- https://bugs.ruby-lang.org/
Issue #20089 has been updated by rmosolgo (Robert Mosolgo). That definitely makes sense for a Fiber killing _itself_, but would you say that killing a _different_ Fiber should cause a fiber to transfer away? In my first script above, calling `worker.kill` causes the `manager` fiber to transfer. I looked a little deeper, it looks like this only happens when both Fibers have been started with `.transfer`. Here's a scenario with two different Fibers, one killing the other, and only the `.transfer`/`.transfer` case exits early: ```ruby puts "\n\nResume/Transfer" fiber1 = Fiber.new { puts "1. Fiber1 Runs" fiber2 = Fiber.new { puts "2. Fiber2 Runs" fiber1.transfer puts "Never: Fiber2 is killed" } fiber2.transfer fiber2.kill puts "3. Fiber1 finishes" } fiber1.resume puts "4. Exit" # Resume/Transfer # 1. Fiber1 Runs # 2. Fiber2 Runs # 3. Fiber1 finishes # 4. Exit puts "\n\nTransfer/Resume" fiber1 = Fiber.new { puts "1. Fiber1 Runs" fiber2 = Fiber.new { puts "2. Fiber2 Runs" Fiber.yield puts "Never: Fiber2 is killed" } fiber2.resume fiber2.kill puts "3. Fiber1 finishes" } fiber1.transfer puts "4. Exit" # Transfer/Resume # 1. Fiber1 Runs # 2. Fiber2 Runs # 3. Fiber1 finishes # 4. Exit puts "\n\nResume/Resume" fiber1 = Fiber.new { puts "1. Fiber1 Runs" fiber2 = Fiber.new { puts "2. Fiber2 Runs" Fiber.yield puts "Never: Fiber2 is killed" } fiber2.resume fiber2.kill puts "3. Fiber1 finishes" } fiber1.resume puts "4. Exit" # Resume/Resume # 1. Fiber1 Runs # 2. Fiber2 Runs # 3. Fiber1 finishes # 4. Exit puts "\n\nTransfer/Transfer" fiber1 = Fiber.new { puts "1. Fiber1 Runs" fiber2 = Fiber.new { puts "2. Fiber2 Runs" fiber1.transfer puts "Never: Fiber2 is killed" } fiber2.transfer fiber2.kill puts "3. Fiber1 finishes" } fiber1.transfer puts "4. Exit" # Transfer/Transfer # 1. Fiber1 Runs # 2. Fiber2 Runs # 4. Exit ``` Is there a more appropriate way to terminate `fiber2` in that case, while keeping control inside `fiber1`, or is this a bug? ---------------------------------------- Bug #20089: Fiber#kill transfers to root fiber https://bugs.ruby-lang.org/issues/20089#change-105925 * Author: rmosolgo (Robert Mosolgo) * Status: Open * Priority: Normal * ruby -v: ruby 3.3.0 (2023-12-25 revision 5124f9ac75) [x86_64-darwin22] * Backport: 3.0: UNKNOWN, 3.1: UNKNOWN, 3.2: UNKNOWN, 3.3: UNKNOWN ---------------------------------------- I was hoping to use `Fiber#kill` to clean up formerly `.transfer`-d Fibers and work around https://bugs.ruby-lang.org/issues/20081, but I found that `Fiber#kill` has a similar control flow jump behavior. Is this on purpose, or a bug? Here's a script to test the behavior: ```ruby manager = Fiber.new do worker = Fiber.new do puts "2. Begin Worker" manager.transfer puts "This should never print -- killed" end puts "1. Transfer to Worker" worker.transfer puts "3. Killing Worker" worker.kill puts "4. Finished manager" end manager.transfer puts "5. Finished script" ``` I expected items `1` through `5` to be printed in order, but in fact, `4` is never printed: ``` $ ruby fiber_transfer_test.rb 1. Transfer to Worker 2. Begin Worker 3. Killing Worker 5. Finished script ``` It seems like `worker.kill` is transferring control to the top-level fiber instead of giving it back to `manager`. I also tried having the thread kill _itself_, hoping it would return to the fiber that originally `.transfer`ed to it, but it also seems to jump out: ```ruby manager = Fiber.new do worker = Fiber.new do puts "2. Begin Worker" manager.transfer Fiber.current.kill puts "This should never print -- killed" end puts "1. Transfer to Worker" worker.transfer puts "3. Killing Worker" worker.transfer puts "4. Finished manager" end manager.transfer puts "5. Finished script" ``` Prints: ``` 1. Transfer to Worker 2. Begin Worker 3. Killing Worker 5. Finished script ``` -- https://bugs.ruby-lang.org/
Issue #20089 has been updated by ioquatix (Samuel Williams). Thanks for the great examples. On the surface of it, it looks like a bug. I'll need to check the logic of the implementation to see if we can improve the behaviour. ---------------------------------------- Bug #20089: Fiber#kill transfers to root fiber https://bugs.ruby-lang.org/issues/20089#change-107849 * Author: rmosolgo (Robert Mosolgo) * Status: Open * ruby -v: ruby 3.3.0 (2023-12-25 revision 5124f9ac75) [x86_64-darwin22] * Backport: 3.0: UNKNOWN, 3.1: UNKNOWN, 3.2: UNKNOWN, 3.3: UNKNOWN ---------------------------------------- I was hoping to use `Fiber#kill` to clean up formerly `.transfer`-d Fibers and work around https://bugs.ruby-lang.org/issues/20081, but I found that `Fiber#kill` has a similar control flow jump behavior. Is this on purpose, or a bug? Here's a script to test the behavior: ```ruby manager = Fiber.new do worker = Fiber.new do puts "2. Begin Worker" manager.transfer puts "This should never print -- killed" end puts "1. Transfer to Worker" worker.transfer puts "3. Killing Worker" worker.kill puts "4. Finished manager" end manager.transfer puts "5. Finished script" ``` I expected items `1` through `5` to be printed in order, but in fact, `4` is never printed: ``` $ ruby fiber_transfer_test.rb 1. Transfer to Worker 2. Begin Worker 3. Killing Worker 5. Finished script ``` It seems like `worker.kill` is transferring control to the top-level fiber instead of giving it back to `manager`. I also tried having the thread kill _itself_, hoping it would return to the fiber that originally `.transfer`ed to it, but it also seems to jump out: ```ruby manager = Fiber.new do worker = Fiber.new do puts "2. Begin Worker" manager.transfer Fiber.current.kill puts "This should never print -- killed" end puts "1. Transfer to Worker" worker.transfer puts "3. Killing Worker" worker.transfer puts "4. Finished manager" end manager.transfer puts "5. Finished script" ``` Prints: ``` 1. Transfer to Worker 2. Begin Worker 3. Killing Worker 5. Finished script ``` -- https://bugs.ruby-lang.org/
Issue #20089 has been updated by ioquatix (Samuel Williams). Assignee set to ioquatix (Samuel Williams) ---------------------------------------- Bug #20089: Fiber#kill transfers to root fiber https://bugs.ruby-lang.org/issues/20089#change-107850 * Author: rmosolgo (Robert Mosolgo) * Status: Open * Assignee: ioquatix (Samuel Williams) * ruby -v: ruby 3.3.0 (2023-12-25 revision 5124f9ac75) [x86_64-darwin22] * Backport: 3.0: UNKNOWN, 3.1: UNKNOWN, 3.2: UNKNOWN, 3.3: UNKNOWN ---------------------------------------- I was hoping to use `Fiber#kill` to clean up formerly `.transfer`-d Fibers and work around https://bugs.ruby-lang.org/issues/20081, but I found that `Fiber#kill` has a similar control flow jump behavior. Is this on purpose, or a bug? Here's a script to test the behavior: ```ruby manager = Fiber.new do worker = Fiber.new do puts "2. Begin Worker" manager.transfer puts "This should never print -- killed" end puts "1. Transfer to Worker" worker.transfer puts "3. Killing Worker" worker.kill puts "4. Finished manager" end manager.transfer puts "5. Finished script" ``` I expected items `1` through `5` to be printed in order, but in fact, `4` is never printed: ``` $ ruby fiber_transfer_test.rb 1. Transfer to Worker 2. Begin Worker 3. Killing Worker 5. Finished script ``` It seems like `worker.kill` is transferring control to the top-level fiber instead of giving it back to `manager`. I also tried having the thread kill _itself_, hoping it would return to the fiber that originally `.transfer`ed to it, but it also seems to jump out: ```ruby manager = Fiber.new do worker = Fiber.new do puts "2. Begin Worker" manager.transfer Fiber.current.kill puts "This should never print -- killed" end puts "1. Transfer to Worker" worker.transfer puts "3. Killing Worker" worker.transfer puts "4. Finished manager" end manager.transfer puts "5. Finished script" ``` Prints: ``` 1. Transfer to Worker 2. Begin Worker 3. Killing Worker 5. Finished script ``` -- https://bugs.ruby-lang.org/
Issue #20089 has been updated by ioquatix (Samuel Williams). In the case of transfer, it may be possible to store the previous fiber, and on exiting a fiber, when no explicit transfer takes place, transfer back to the fiber that originally transferred into it. I think this is fairly compatible with existing code, but we'd need to survey the impact. ---------------------------------------- Bug #20089: Fiber#kill transfers to root fiber https://bugs.ruby-lang.org/issues/20089#change-107963 * Author: rmosolgo (Robert Mosolgo) * Status: Open * Assignee: ioquatix (Samuel Williams) * ruby -v: ruby 3.3.0 (2023-12-25 revision 5124f9ac75) [x86_64-darwin22] * Backport: 3.0: UNKNOWN, 3.1: UNKNOWN, 3.2: UNKNOWN, 3.3: UNKNOWN ---------------------------------------- I was hoping to use `Fiber#kill` to clean up formerly `.transfer`-d Fibers and work around https://bugs.ruby-lang.org/issues/20081, but I found that `Fiber#kill` has a similar control flow jump behavior. Is this on purpose, or a bug? Here's a script to test the behavior: ```ruby manager = Fiber.new do worker = Fiber.new do puts "2. Begin Worker" manager.transfer puts "This should never print -- killed" end puts "1. Transfer to Worker" worker.transfer puts "3. Killing Worker" worker.kill puts "4. Finished manager" end manager.transfer puts "5. Finished script" ``` I expected items `1` through `5` to be printed in order, but in fact, `4` is never printed: ``` $ ruby fiber_transfer_test.rb 1. Transfer to Worker 2. Begin Worker 3. Killing Worker 5. Finished script ``` It seems like `worker.kill` is transferring control to the top-level fiber instead of giving it back to `manager`. I also tried having the thread kill _itself_, hoping it would return to the fiber that originally `.transfer`ed to it, but it also seems to jump out: ```ruby manager = Fiber.new do worker = Fiber.new do puts "2. Begin Worker" manager.transfer Fiber.current.kill puts "This should never print -- killed" end puts "1. Transfer to Worker" worker.transfer puts "3. Killing Worker" worker.transfer puts "4. Finished manager" end manager.transfer puts "5. Finished script" ``` Prints: ``` 1. Transfer to Worker 2. Begin Worker 3. Killing Worker 5. Finished script ``` -- https://bugs.ruby-lang.org/
participants (2)
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ioquatix (Samuel Williams) -
rmosolgo (Robert Mosolgo)