Issue #18464 has been updated by nagachika (Tomoyuki Chikanaga). Backport changed from 2.6: DONTNEED, 2.7: DONTNEED, 3.0: REQUIRED, 3.1: DONE, 3.2: REQUIRED to 2.6: DONTNEED, 2.7: DONTNEED, 3.0: REQUIRED, 3.1: DONE, 3.2: DONE ruby_3_2 b422c3523c419b88c6da23a4022ae8864f411b84 merged revision(s) 7bd7aee02e303de27d2cddfc5ef47e612d6782cb. ---------------------------------------- Bug #18464: RUBY_INTERNAL_EVENT_NEWOBJ tracepoint causes an interpreter crash when combined with Ractors https://bugs.ruby-lang.org/issues/18464#change-103684 * Author: kjtsanaktsidis (KJ Tsanaktsidis) * Status: Closed * Priority: Normal * Assignee: ko1 (Koichi Sasada) * ruby -v: ruby 3.1.0p0 (2021-12-25 revision fb4df44d16) [x86_64-darwin20] * Backport: 2.6: DONTNEED, 2.7: DONTNEED, 3.0: REQUIRED, 3.1: DONE, 3.2: DONE ---------------------------------------- When a Ractor is created whilst a tracepoint for `RUBY_INTERNAL_EVENT_NEWOBJ` is active (registered with `rb_tracepoint_new`/`rb_tracepoint_enabled`), the interpreter crashes with a null pointer dereference with the following backtrace: ``` [BUG] Segmentation fault at 0x0000000000000000 ruby 3.1.0p0 (2021-12-25 revision fb4df44d16) [x86_64-darwin20] ... -- C level backtrace information ------------------------------------------- /Users/ktsanaktsidis/Code/zendesk/ruby/ruby(rb_print_backtrace+0xf) [0x10a15fadd] vm_dump.c:759 /Users/ktsanaktsidis/Code/zendesk/ruby/ruby(rb_vm_bugreport) vm_dump.c:1045 /Users/ktsanaktsidis/Code/zendesk/ruby/ruby(rb_vm_bugreport) (null):0 /Users/ktsanaktsidis/Code/zendesk/ruby/ruby(bug_report_end+0x0) [0x109f96b81] error.c:820 /Users/ktsanaktsidis/Code/zendesk/ruby/ruby(rb_bug_for_fatal_signal) error.c:820 /Users/ktsanaktsidis/Code/zendesk/ruby/ruby(sigsegv+0x52) [0x10a0be3a2] signal.c:964 /usr/lib/system/libsystem_platform.dylib(_sigtramp+0x1d) [0x7fff20934d7d] /Users/ktsanaktsidis/Code/zendesk/ruby/ruby(gc_event_hook_body+0x4) [0x109fb9d21] gc.c:2214 /Users/ktsanaktsidis/Code/zendesk/ruby/ruby(newobj_slowpath) gc.c:2486 /Users/ktsanaktsidis/Code/zendesk/ruby/ruby(newobj_slowpath_wb_unprotected) gc.c:2507 /Users/ktsanaktsidis/Code/zendesk/ruby/ruby(newobj_fill+0x0) [0x109fac92e] gc.c:2543 /Users/ktsanaktsidis/Code/zendesk/ruby/ruby(newobj_of0) gc.c:2553 /Users/ktsanaktsidis/Code/zendesk/ruby/ruby(newobj_of) gc.c:2552 /Users/ktsanaktsidis/Code/zendesk/ruby/ruby(rb_wb_unprotected_newobj_of) gc.c:2567 /Users/ktsanaktsidis/Code/zendesk/ruby/ruby(io_alloc+0x12) [0x109fd341c] io.c:1047 /Users/ktsanaktsidis/Code/zendesk/ruby/ruby(prep_io) io.c:8483 /Users/ktsanaktsidis/Code/zendesk/ruby/ruby(prep_stdio) io.c:8514 /Users/ktsanaktsidis/Code/zendesk/ruby/ruby(rb_io_prep_stdin) io.c:8532 /Users/ktsanaktsidis/Code/zendesk/ruby/ruby(thread_start_func_2+0xf7) [0x10a1058a7] thread.c:802 /Users/ktsanaktsidis/Code/zendesk/ruby/ruby(rb_native_cond_initialize+0x0) [0x10a1055fb] ./thread_pthread.c:1047 /Users/ktsanaktsidis/Code/zendesk/ruby/ruby(register_cached_thread_and_wait) ./thread_pthread.c:1099 /Users/ktsanaktsidis/Code/zendesk/ruby/ruby(thread_start_func_1) ./thread_pthread.c:1054 /usr/lib/system/libsystem_pthread.dylib(_pthread_start+0xe0) [0x7fff208ef8fc] ``` (full output is attached). This seems to be because the new Ractor sets up stdio objects (`rb_io_prep_stdin` et. al.), which in turn allocate Ruby objects, before `rb_ec_initialize_vm_stack` is called to set up the initial stack frame. I've attached a patch which works around this by not firing GC event hooks if there is no control frame on the execution context. The patch also includes a test which reproduces the issue using the `objspace` extension; creating a Ractor within an `ObjectSpace.trace_object_allocations` block is enough to trigger the crash. The patch seems to fix things, but if you folk prefer I can also try swapping around the order of `prep_stdio` and `rb_ec_initialize_vm_stack`. ---Files-------------------------------- 0001-Fix-interpreter-crash-caused-by-RUBY_INTERNAL_EVENT_.patch (1.91 KB) crash.log (26.1 KB) ruby_2022-01-08-151326_8927-ktsanaktsidis.crash (18.8 KB) -- https://bugs.ruby-lang.org/