From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from smtp-out1.suse.de (smtp-out1.suse.de [IPv6:2001:67c:2178:6::1c]) by sourceware.org (Postfix) with ESMTPS id B020B3858C83 for ; Thu, 14 Jul 2022 06:19:27 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.1 sourceware.org B020B3858C83 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-out1.suse.de (Postfix) with ESMTPS id BFC3F349B0 for ; Thu, 14 Jul 2022 06:19:26 +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 AF07513A23 for ; Thu, 14 Jul 2022 06:19:26 +0000 (UTC) Received: from dovecot-director2.suse.de ([192.168.254.65]) by imap2.suse-dmz.suse.de with ESMTPSA id UsuxKW61z2K8JQAAMHmgww (envelope-from ) for ; Thu, 14 Jul 2022 06:19:26 +0000 Date: Thu, 14 Jul 2022 08:19:25 +0200 From: Tom de Vries To: gdb-patches@sourceware.org Subject: [committed][gdb/symtab] Fix data race in ~charset_vector Message-ID: <20220714061923.GA543@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=-12.9 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, 14 Jul 2022 06:19:30 -0000 Hi, When doing: ... $ gdb ./outputs/gdb.ada/char_enum_unicode/foo -batch -ex "break foo.adb:26" ... with a gdb build with -fsanitize=thread I run into a data race: ... WARNING: ThreadSanitizer: data race (pid=30917) Write of size 8 at 0x7b0400004070 by main thread: #0 free (libtsan.so.2+0x4c5e2) #1 xfree gdbsupport/gdb-xfree.h:37 (gdb+0x650f17) #2 charset_vector::clear() gdb/charset.c:703 (gdb+0x651354) #3 charset_vector::~charset_vector() gdb/charset.c:697 (gdb+0x6512d3) #4 (libtsan.so.2+0x32643) #5 captured_main_1 gdb/main.c:1310 (gdb+0xa3975a) ... The problem is that we're freeing the charset_vector elements in the destructor, which may still be used by a worker thread. Fix this by not freeing the charset_vector elements in the destructor. Tested on x86_64-linux. Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=29311 Committed to trunk. Thanks, - Tom [gdb/symtab] Fix data race in ~charset_vector --- gdb/charset.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) diff --git a/gdb/charset.c b/gdb/charset.c index 74f742e0aa7..a6261fc505c 100644 --- a/gdb/charset.c +++ b/gdb/charset.c @@ -694,7 +694,13 @@ struct charset_vector { ~charset_vector () { - clear (); + /* Note that we do not call charset_vector::clear, which would also xfree + the elements. This destructor is only called after exit, at which point + those will be freed anyway on process exit, so not freeing them now is + not classified as a memory leak. OTOH, freeing them now might be + classified as a data race, because some worker thread might still be + accessing them. */ + charsets.clear (); } void clear ()