From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from smtp-out2.suse.de (smtp-out2.suse.de [195.135.220.29]) by sourceware.org (Postfix) with ESMTPS id CA1DC3841459 for ; Thu, 30 Jun 2022 09:58:33 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.1 sourceware.org CA1DC3841459 Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by smtp-out2.suse.de (Postfix) with ESMTPS id 00F3B1F9F3; Thu, 30 Jun 2022 09:58:33 +0000 (UTC) Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by imap2.suse-dmz.suse.de (Postfix) with ESMTPS id D893A13A5C; Thu, 30 Jun 2022 09:58:32 +0000 (UTC) Received: from dovecot-director2.suse.de ([192.168.254.65]) by imap2.suse-dmz.suse.de with ESMTPSA id fwbJM8hzvWJsbwAAMHmgww (envelope-from ); Thu, 30 Jun 2022 09:58:32 +0000 Date: Thu, 30 Jun 2022 11:58:31 +0200 From: Tom de Vries To: gdb-patches@sourceware.org Cc: Pedro Alves , Tom Tromey Subject: [PATCH][gdb] Block SIGTERM in worker threads Message-ID: <20220630095824.GA24025@delia.home> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.10.1 (2018-07-13) X-Spam-Status: No, score=-12.7 required=5.0 tests=BAYES_00, DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, DKIM_VALID_EF, GIT_PATCH_0, SPF_HELO_NONE, SPF_PASS, TXREP, T_SCC_BODY_TEXT_LINE autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on server2.sourceware.org X-BeenThere: gdb-patches@sourceware.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Gdb-patches mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 30 Jun 2022 09:58:35 -0000 Hi, With gdb build with gcc-12 and -fsanitize=thread, and test-case gdb.base/gdb-sigterm.exp, I run into: ... WARNING: ThreadSanitizer: data race (pid=9722)^M Write of size 4 at 0x00000325bc68 by thread T1:^M #0 handle_sigterm(int) src/gdb/event-top.c:1211 (gdb+0x8ec01f)^M ... Previous read of size 4 at 0x00000325bc68 by main thread:^M [failed to restore the stack]^M ^M Location is global 'sync_quit_force_run' of size 4 at \ 0x00000325bc68 (gdb+0x325bc68)^M ... SUMMARY: ThreadSanitizer: data race gdb/event-top.c:1211 in \ handle_sigterm(int)^M ... and 3 more data races involving handle_sigterm and locations: - active_ext_lang - quit_flag - heap block of size 40 (XNEW (async_signal_handler) in create_async_signal_handler) This was reported in PR29297. The testcase executes a "kill -TERM $gdb_pid", which generates a process-directed signal. A process-directed signal can be delivered to any thread, and what we see here is the fallout of the signal being delivered to a worker thread rather than the main thread. Fix this by blocking SIGTERM in the worker threads. [ I have not been able to reproduce this after it occurred for the first time, so unfortunately I cannot confirm that the patch fixes the problem. ] Tested on x86_64-linux, with and without -fsanitize=thread. Any comments? Thanks, - Tom [gdb] Block SIGTERM in worker threads --- gdbsupport/block-signals.h | 1 + 1 file changed, 1 insertion(+) diff --git a/gdbsupport/block-signals.h b/gdbsupport/block-signals.h index cf97208c750..4703690a4ec 100644 --- a/gdbsupport/block-signals.h +++ b/gdbsupport/block-signals.h @@ -42,6 +42,7 @@ class block_signals sigaddset (&mask, SIGCHLD); sigaddset (&mask, SIGALRM); sigaddset (&mask, SIGWINCH); + sigaddset (&mask, SIGTERM); gdb_sigmask (SIG_BLOCK, &mask, &m_old_mask); #endif }