From: briantkephart@... Date: 2018-03-11T19:38:55+00:00 Subject: [ruby-core:86081] [Ruby trunk Bug#14561] Consistent 2.5.0 seg fault in GC, related to accessing an enumerator in a thread Issue #14561 has been updated by brian-kephart (Brian Kephart). I think I'm running into the same bug. I'm new to reading these types of traces, so please let me know if this needs to be a separate issue instead. Running Ruby 2.5.0 on OS X. ~~~ /Users/briankephart/.rvm/rubies/ruby-2.5.0/lib/ruby/2.5.0/socket.rb:227: [BUG] Segmentation fault at 0x000000010dd5fa3a ruby 2.5.0p0 (2017-12-25 revision 61468) [x86_64-darwin17] -- Crash Report log information -------------------------------------------- See Crash Report log file under the one of following: * ~/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 ----------------------------------------------- c:0014 p:---- s:0136 e:000135 CFUNC :getaddrinfo c:0013 p:0034 s:0126 e:000125 METHOD /Users/briankephart/.rvm/rubies/ruby-2.5.0/lib/ruby/2.5.0/socket.rb:227 c:0012 p:0073 s:0115 e:000114 METHOD /Users/briankephart/.rvm/rubies/ruby-2.5.0/lib/ruby/2.5.0/socket.rb:631 c:0011 p:0034 s:0102 e:000101 METHOD /Users/briankephart/.rvm/gems/ruby-2.5.0/gems/webpacker-3.2.2/lib/webpacker/dev_server.rb:14 c:0010 p:0032 s:0098 e:000097 METHOD /Users/briankephart/.rvm/gems/ruby-2.5.0/gems/webpacker-3.2.2/lib/webpacker/dev_server_proxy.rb:7 c:0009 p:0014 s:0090 E:001848 METHOD /Users/briankephart/.rvm/gems/ruby-2.5.0/gems/rack-proxy-0.6.3/lib/rack/proxy.rb:57 c:0008 p:0041 s:0085 E:0018d8 METHOD /Users/briankephart/.rvm/gems/ruby-2.5.0/gems/skylight-core-2.0.0.beta2/lib/skylight/core/probes/middleware.rb:28 c:0007 p:0020 s:0074 E:001940 METHOD /Users/briankephart/.rvm/gems/ruby-2.5.0/gems/railties-5.2.0.rc1/lib/rails/engine.rb:524 c:0006 p:0026 s:0068 E:001998 METHOD /Users/briankephart/.rvm/gems/ruby-2.5.0/gems/puma-3.11.2/lib/puma/configuration.rb:225 c:0005 p:0258 s:0063 E:001a98 METHOD /Users/briankephart/.rvm/gems/ruby-2.5.0/gems/puma-3.11.2/lib/puma/server.rb:624 c:0004 p:0026 s:0038 E:002590 METHOD /Users/briankephart/.rvm/gems/ruby-2.5.0/gems/puma-3.11.2/lib/puma/server.rb:438 c:0003 p:0065 s:0026 E:0025e8 BLOCK /Users/briankephart/.rvm/gems/ruby-2.5.0/gems/puma-3.11.2/lib/puma/server.rb:302 [FINISH] c:0002 p:0125 s:0016 E:002690 BLOCK /Users/briankephart/.rvm/gems/ruby-2.5.0/gems/puma-3.11.2/lib/puma/thread_pool.rb:120 [FINISH] c:0001 p:---- s:0003 e:000002 (none) [FINISH] -- Ruby level backtrace information ---------------------------------------- /Users/briankephart/.rvm/gems/ruby-2.5.0/gems/puma-3.11.2/lib/puma/thread_pool.rb:120:in `block in spawn_thread' /Users/briankephart/.rvm/gems/ruby-2.5.0/gems/puma-3.11.2/lib/puma/server.rb:302:in `block in run' /Users/briankephart/.rvm/gems/ruby-2.5.0/gems/puma-3.11.2/lib/puma/server.rb:438:in `process_client' /Users/briankephart/.rvm/gems/ruby-2.5.0/gems/puma-3.11.2/lib/puma/server.rb:624:in `handle_request' /Users/briankephart/.rvm/gems/ruby-2.5.0/gems/puma-3.11.2/lib/puma/configuration.rb:225:in `call' /Users/briankephart/.rvm/gems/ruby-2.5.0/gems/railties-5.2.0.rc1/lib/rails/engine.rb:524:in `call' /Users/briankephart/.rvm/gems/ruby-2.5.0/gems/skylight-core-2.0.0.beta2/lib/skylight/core/probes/middleware.rb:28:in `call' /Users/briankephart/.rvm/gems/ruby-2.5.0/gems/rack-proxy-0.6.3/lib/rack/proxy.rb:57:in `call' /Users/briankephart/.rvm/gems/ruby-2.5.0/gems/webpacker-3.2.2/lib/webpacker/dev_server_proxy.rb:7:in `rewrite_response' /Users/briankephart/.rvm/gems/ruby-2.5.0/gems/webpacker-3.2.2/lib/webpacker/dev_server.rb:14:in `running?' /Users/briankephart/.rvm/rubies/ruby-2.5.0/lib/ruby/2.5.0/socket.rb:631:in `tcp' /Users/briankephart/.rvm/rubies/ruby-2.5.0/lib/ruby/2.5.0/socket.rb:227:in `foreach' /Users/briankephart/.rvm/rubies/ruby-2.5.0/lib/ruby/2.5.0/socket.rb:227:in `getaddrinfo' -- Machine register context ------------------------------------------------ rax: 0x0000000000000000 rbx: 0x00007fc5eef71ec0 rcx: 0x0000000000010000 rdx: 0x000070000c3b3c80 rdi: 0x000000010dd5fa38 rsi: 0x00007fc5eef71ec0 rbp: 0x000070000c3b3c70 rsp: 0x000070000c3b3c38 r8: 0x0000000000000000 r9: 0xffffffff00000000 r10: 0x000000010d7fa738 r11: 0xfffff0009ac08e64 r12: 0x00007fffaa5a5f40 r13: 0x00007fff717f2864 r14: 0x000070000c3b3c80 r15: 0x00007fc5eef71ed0 rip: 0x00007fff717f2868 rfl: 0x0000000000010206 -- C level backtrace information ------------------------------------------- 0 libruby.2.5.dylib 0x000000010d9ebd07 rb_vm_bugreport + 135 1 libruby.2.5.dylib 0x000000010d870978 rb_bug_context + 472 2 libruby.2.5.dylib 0x000000010d960151 sigsegv + 81 3 libsystem_platform.dylib 0x00007fff717c6f5a _sigtramp + 26 4 libsystem_trace.dylib 0x00007fff717f2868 _os_log_cmp_key + 4 -- Other runtime information ----------------------------------------------- * Loaded script: puma: cluster worker 0: 2204 [brian-becca] * Loaded features: 0 enumerator.so 1 thread.rb 2 rational.so 3 complex.so ... lots more ~~~ ---------------------------------------- Bug #14561: Consistent 2.5.0 seg fault in GC, related to accessing an enumerator in a thread https://bugs.ruby-lang.org/issues/14561#change-70947 * Author: dazuma (Daniel Azuma) * Status: Open * Priority: Normal * Assignee: * Target version: * ruby -v: ruby 2.5.0p0 (2017-12-25 revision 61468) [x86_64-darwin17] * Backport: 2.3: UNKNOWN, 2.4: UNKNOWN, 2.5: UNKNOWN ---------------------------------------- This seg fault happens consistently on OSX (specifically I'm reproing it on a late 2015 Macbook pro running 10.13.3, but it seems to happen on similar machines as well). It happens only on Ruby 2.5.0. Small repro case: ```ruby enum = Enumerator.new { |y| y << 1 } thread = Thread.new { enum.peek } # enum.next also causes the segfault, but not enum.size thread.join GC.start # <- seg fault here ``` The C-level backtrace identifies this as within the mark phase of GC: ``` -- C level backtrace information ------------------------------------------- 0 ruby 0x000000010f77ced7 rb_vm_bugreport + 135 1 ruby 0x000000010f602628 rb_bug_context + 472 2 ruby 0x000000010f6f1491 sigsegv + 81 3 libsystem_platform.dylib 0x00007fff6a779f5a _sigtramp + 26 4 ruby 0x000000010f61bb93 rb_gc_mark_machine_stack + 99 5 ruby 0x000000010f76bf39 rb_execution_context_mark + 137 6 ruby 0x000000010f5ea32b cont_mark + 27 7 ruby 0x000000010f626a02 gc_marks_rest + 146 8 ruby 0x000000010f6253c0 gc_start + 2816 9 ruby 0x000000010f61d628 garbage_collect + 184 10 ruby 0x000000010f622215 gc_start_internal + 485 11 ruby 0x000000010f7703be vm_call_cfunc + 286 12 ruby 0x000000010f759af4 vm_exec_core + 12260 13 ruby 0x000000010f76ac8e vm_exec + 142 14 ruby 0x000000010f60c101 ruby_exec_internal + 177 15 ruby 0x000000010f60bff8 ruby_run_node + 56 16 ruby 0x000000010f592d1f main + 79 I also ran this against Ruby recompiled with -O0, and got a more detailed backtrace: -- C level backtrace information ------------------------------------------- 0 libruby.2.5.dylib 0x000000010c416e19 rb_print_backtrace + 25 1 libruby.2.5.dylib 0x000000010c416f28 rb_vm_bugreport + 136 2 libruby.2.5.dylib 0x000000010c2096f2 rb_bug_context + 450 3 libruby.2.5.dylib 0x000000010c35b4ee sigsegv + 94 4 libsystem_platform.dylib 0x00007fff6a779f5a _sigtramp + 26 5 libruby.2.5.dylib 0x000000010c2395a1 mark_locations_array + 49 6 libruby.2.5.dylib 0x000000010c22a5bb gc_mark_locations + 75 7 libruby.2.5.dylib 0x000000010c22a7d9 mark_stack_locations + 41 8 libruby.2.5.dylib 0x000000010c22a79f rb_gc_mark_machine_stack + 79 9 libruby.2.5.dylib 0x000000010c3f8868 rb_execution_context_mark + 264 10 libruby.2.5.dylib 0x000000010c1e263e cont_mark + 46 11 libruby.2.5.dylib 0x000000010c1e2572 fiber_mark + 146 12 libruby.2.5.dylib 0x000000010c22f4c6 gc_mark_children + 1094 13 libruby.2.5.dylib 0x000000010c23734c gc_mark_stacked_objects + 108 14 libruby.2.5.dylib 0x000000010c237a5b gc_mark_stacked_objects_all + 27 15 libruby.2.5.dylib 0x000000010c236cb1 gc_marks_rest + 129 16 libruby.2.5.dylib 0x000000010c238787 gc_marks + 103 17 libruby.2.5.dylib 0x000000010c2352e2 gc_start + 802 18 libruby.2.5.dylib 0x000000010c22ca18 garbage_collect + 56 19 libruby.2.5.dylib 0x000000010c231f7d gc_start_internal + 493 20 libruby.2.5.dylib 0x000000010c401f2a call_cfunc_m1 + 42 21 libruby.2.5.dylib 0x000000010c400d1d vm_call_cfunc_with_frame + 605 22 libruby.2.5.dylib 0x000000010c3fc41d vm_call_cfunc + 173 23 libruby.2.5.dylib 0x000000010c3fb8fe vm_call_method_each_type + 190 24 libruby.2.5.dylib 0x000000010c3fb690 vm_call_method + 160 25 libruby.2.5.dylib 0x000000010c3fb5e5 vm_call_general + 53 26 libruby.2.5.dylib 0x000000010c3e784e vm_exec_core + 8974 27 libruby.2.5.dylib 0x000000010c3f6fe6 vm_exec + 182 28 libruby.2.5.dylib 0x000000010c3f7d5b rb_iseq_eval_main + 43 29 libruby.2.5.dylib 0x000000010c214208 ruby_exec_internal + 232 30 libruby.2.5.dylib 0x000000010c214111 ruby_exec_node + 33 31 libruby.2.5.dylib 0x000000010c2140d0 ruby_run_node + 64 32 ruby 0x000000010c16ff2f main + 95 ``` As far as I can tell, the C instruction triggering the segfault is here in gc.c (around line 4064): ```C static void mark_locations_array(rb_objspace_t *objspace, register const VALUE *x, register long n) { VALUE v; while (n--) { v = *x; // <----- Seems to be crashing here? gc_mark_maybe(objspace, v); x++; } } ``` Indicating a bad pointer in the machine stack. I'm not sufficiently familiar with the VM internals to make much further progress, but I hope the repro case is helpful. It seems to require accessing an `Enumerator` element within a separate thread, and then waiting for the thread to end. -- https://bugs.ruby-lang.org/ Unsubscribe: