Issue #21257 has been updated by k0kubun (Takashi Kokubun). Backport changed from 3.2: DONTNEED, 3.3: REQUIRED, 3.4: REQUIRED to 3.2: DONTNEED, 3.3: REQUIRED, 3.4: DONE ruby_3_4 commit:50b1759be00713535c41f5650feb3967c533450a. ---------------------------------------- Bug #21257: YJIT can generate infinite loop when OOM https://bugs.ruby-lang.org/issues/21257#change-113228 * Author: rianmcguire (Rian McGuire) * Status: Closed * Assignee: jit * Backport: 3.2: DONTNEED, 3.3: REQUIRED, 3.4: DONE ---------------------------------------- We've found an edge case where YJIT can generate an infinite loop (jump to the same address) when it's out-of-memory. Reproduction: ```ruby def first second end def second ::File end # Make `second` side exit on its first instruction trace = TracePoint.new(:line) { } trace.enable(target: method(:second)) 32.times do |i| puts i first if i == 29 # We've JITed the methods now - trigger the bug # Trigger a constant cache miss in rb_vm_opt_getconstant_path (in `second`) next time it's called module InvalidateConstantCache File = nil end # nb. this only works in yjit dev mode RubyVM::YJIT.simulate_oom! end end ``` This hangs indefinitely when run with YJIT (`./configure --enable-yjit=dev` is required for simulate_oom). If we attach a debugger to the Ruby process at this point, it's stuck in an infinite loop: ``` $ lldb -p 9753 (lldb) process attach --pid 9753 Process 9753 stopped * thread #1, queue = 'com.apple.main-thread', stop reason = signal SIGSTOP frame #0: 0x0000000104b202b8 -> 0x104b202b8: b 0x104b202b8 0x104b202bc: nop 0x104b202c0: nop 0x104b202c4: nop Target 0: (ruby) stopped. Executable module set to "/Users/rian/opt/ruby/bin/ruby". Architecture set to: arm64-apple-macosx-. ``` We've reproduced this on: ``` ruby 3.3.6 (2024-11-05 revision 75015d4c1f) [x86_64-linux] ruby 3.4.2 (2025-02-15 revision d2930f8e7a) +PRISM [arm64-darwin23] ruby 3.5.0dev (2025-04-08T06:46:45Z master b68fe530f1) +PRISM [arm64-darwin23] ``` -- https://bugs.ruby-lang.org/