From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.2 (2018-09-13) on dcvr.yhbt.net X-Spam-Level: X-Spam-ASN: AS4713 221.184.0.0/13 X-Spam-Status: No, score=-2.6 required=3.0 tests=BAYES_00,DKIM_ADSP_CUSTOM_MED, FORGED_GMAIL_RCVD,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,RCVD_IN_DNSWL_MED, SPF_HELO_NONE,SPF_PASS shortcircuit=no autolearn=no autolearn_force=no version=3.4.2 Received: from neon.ruby-lang.org (neon.ruby-lang.org [221.186.184.75]) by dcvr.yhbt.net (Postfix) with ESMTP id D9BDA1F463 for ; Thu, 19 Dec 2019 19:46:34 +0000 (UTC) Received: from neon.ruby-lang.org (localhost [IPv6:::1]) by neon.ruby-lang.org (Postfix) with ESMTP id 6568412090B; Fri, 20 Dec 2019 04:46:22 +0900 (JST) Received: from o1678948x4.outbound-mail.sendgrid.net (o1678948x4.outbound-mail.sendgrid.net [167.89.48.4]) by neon.ruby-lang.org (Postfix) with ESMTPS id 57720120900 for ; Fri, 20 Dec 2019 04:46:20 +0900 (JST) Received: by filterdrecv-p3las1-5bf99c48d-fkthr with SMTP id filterdrecv-p3las1-5bf99c48d-fkthr-20-5DFBD38A-47 2019-12-19 19:46:18.568495183 +0000 UTC m=+241237.887240718 Received: from herokuapp.com (unknown [3.92.31.214]) by ismtpd0039p1iad1.sendgrid.net (SG) with ESMTP id rco5w3dLR3CSvVb85lo9FA for ; Thu, 19 Dec 2019 19:46:18.402 +0000 (UTC) Date: Thu, 19 Dec 2019 19:46:18 +0000 (UTC) From: davidnwelton@gmail.com Message-ID: References: Mime-Version: 1.0 X-Redmine-MailingListIntegration-Message-Ids: 72004 X-Redmine-Project: ruby-trunk X-Redmine-Issue-Id: 16288 X-Redmine-Issue-Author: davidw X-Redmine-Sender: davidw X-Mailer: Redmine X-Redmine-Host: bugs.ruby-lang.org X-Redmine-Site: Ruby Issue Tracking System X-Auto-Response-Suppress: All Auto-Submitted: auto-generated X-SG-EID: =?us-ascii?Q?9w824K3b0SHUB398CXnSgxNNt5RmCpnG5xjUB9l+wgS2JT1UOspzU6JNPGyiZs?= =?us-ascii?Q?W4ZX60kR+eoV5Tmi8NVifZI68lzBtPj5qEinWyd?= =?us-ascii?Q?m53PUx7zDOyZRTeUg66HFIU6k+OjFYRIrUwFcUO?= =?us-ascii?Q?7+D4KoNzJB7trdZa89r0TNXMi5SjBkW+TzhQSoD?= =?us-ascii?Q?oRuurK8hiG1FVImhJqfcbq4ohLPuKIk4z4f=2F3Po?= =?us-ascii?Q?yZ0zIScTT2UJfKl5A=3D?= To: ruby-core@ruby-lang.org X-ML-Name: ruby-core X-Mail-Count: 96343 Subject: [ruby-core:96343] [Ruby master Bug#16288] Segmentation fault with finalizers, threads X-BeenThere: ruby-core@ruby-lang.org X-Mailman-Version: 2.1.15 Precedence: list Reply-To: Ruby developers List-Id: Ruby developers List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: ruby-core-bounces@ruby-lang.org Sender: "ruby-core" Issue #16288 has been updated by davidw (David Welton). > --- a/thread.c > +++ b/thread.c > @@ -682,7 +682,7 @@ thread_do_start(rb_thread_t *th) > else { > args_ptr = RARRAY_CONST_PTR(args); > } > - > + rb_funcallv(NULL, idInspect, 0, 0); > th->value = rb_vm_invoke_proc(th->ec, proc, > (int)args_len, args_ptr, > VM_BLOCK_HANDLER_NONE); > I replaced the funcall with RUBY_VM_CHECK_INTS(GET_EC()); And everything seems to work ok. I realized that even in 'normal' circumstances, Ruby does not wait for threads to finish; the programmer must request that, so I'm not sure that's actually correct. With the above patch, I don't get the segfault any more. I don't have nearly enough familiarity with the internals to know if this is actually the best or most correct way of fixing the problem though. Thank you ---------------------------------------- Bug #16288: Segmentation fault with finalizers, threads https://bugs.ruby-lang.org/issues/16288#change-83251 * Author: davidw (David Welton) * Status: Open * Priority: Normal * Assignee: * Target version: * ruby -v: ruby 2.6.6p116 (2019-10-02 revision 67825) [x86_64-linux] * Backport: 2.5: UNKNOWN, 2.6: UNKNOWN ---------------------------------------- Hi, This is a tricky one and I am still working on narrowing it down, but I will report what I have so far. I compiled a version of 2_6_6 from github: ruby 2.6.6p116 (2019-10-02 revision 67825) [x86_64-linux] I have a minimal Rails project that uses Mongoid. It crashes with a segmentation fault when rspec runs. The concurrent ruby gem is in some way involved, and I have been posting there: https://github.com/ruby-concurrency/concurrent-ruby/issues/808 However, I think there is a deeper problem - I would not expect a user level script to cause a segmentation fault. I have been putting a lot of debugging statements in, and turned on Thread.DEBUG, and have noticed some things. I am not experienced with Ruby's internals, so some of these bits of data might be normal or irrelevant: * The concurrent-ruby gem uses ObjectSpace.define_finalizer to set a finalizer * That finalizer creates a new Thread * However, it appears as if that thread is running after the main thread is already dead, so code that expects to reference the main thread crashes, because it's a NULL reference. I tried the following test code: ``` class Foo def initialize ObjectSpace.define_finalizer(self, proc do Foo.foo_finalizer end) end def bar puts 'bar' end def Foo.foo_finalizer puts "foo_finalizer" t = Thread.new do puts "Thread reporting for duty" end puts "foo_finalizer thread launched" sleep 5 end end f = Foo.new f.bar f = nil ``` While trying to develop a simple test case to demonstrate the problem. It triggers rb_raise(rb_eThreadError, "can't alloc thread"); in thread_s_new, because it looks like the main thread has already been marked as 'killed' in this case. When I check the main thread status in thread_s_new with the above code, it reports 'dead'. When I run my rspec code in the sample Rails project, thread_s_new shows the main thread's status as 'run' even if it should be dead? I have seen some debugging things that shows some exceptions and thread_join interrupts and so on. Is it possible that something like this is happening? Main thread starts doing a cleanup, and gets an exception or something that generates an interrupt, and its KILLED status gets reset to RUNNABLE Then, in the finalizer, it starts creating a Thread, but at this point the main thread actually does get killed, and when that finalizer thread tries to run it runs into a null reference? I can provide the Rails sample project if needs be. Sorry if any of the above isn't clear; I've been staring at the C code for several hours and am a bit cross-eyed! Thank you for any insights. -- https://bugs.ruby-lang.org/