From 14dd1080c6127e7ad7566598860a885aa244ff8d Mon Sep 17 00:00:00 2001 From: Tom de Vries Date: Thu, 14 Jul 2022 08:19:00 +0200 Subject: [PATCH] [gdb/symtab] Make per_cu->m_lang atomic When building gdb with -fsanitize=thread and running test-case gdb.dwarf2/inlined_subroutine-inheritance.exp, we run into a data race between: ... Read of size 1 at 0x7b2000003010 by thread T4: #0 packed::operator language() const packed.h:54 #1 dwarf2_per_cu_data::set_lang(language) read.h:363 ... and: ... Previous write of size 1 at 0x7b2000003010 by main thread: #0 dwarf2_per_cu_data::set_lang(language) read.h:365 ... Fix this by making per_cu->m_lang atomic. Tested on x86_64-linux. Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=29286 --- gdb/dwarf2/read.h | 22 +++++++++++++--------- 1 file changed, 13 insertions(+), 9 deletions(-) diff --git a/gdb/dwarf2/read.h b/gdb/dwarf2/read.h index acbe298b310..c2f86a9d367 100644 --- a/gdb/dwarf2/read.h +++ b/gdb/dwarf2/read.h @@ -181,7 +181,7 @@ private: std::atomic> m_unit_type {(dwarf_unit_type)0}; /* The language of this CU. */ - packed m_lang = language_unknown; + std::atomic> m_lang {language_unknown}; public: /* True if this CU has been scanned by the indexer; false if @@ -351,21 +351,25 @@ public: enum language lang (bool strict_p = true) const { + enum language l = m_lang.load (); if (strict_p) - gdb_assert (m_lang != language_unknown); - return m_lang; + gdb_assert (l != language_unknown); + return l; } void set_lang (enum language lang) { if (unit_type () == DW_UT_partial) return; - if (m_lang == language_unknown) - /* Set if not set already. */ - m_lang = lang; - else - /* If already set, verify that it's the same value. */ - gdb_assert (m_lang == lang); + /* Set if not set already. */ + packed nope = language_unknown; + if (m_lang.compare_exchange_strong (nope, lang)) + return; + /* If already set, verify that it's the same value. */ + nope = lang; + if (m_lang.compare_exchange_strong (nope, lang)) + return; + gdb_assert_not_reached (); } /* Free any cached file names. */ -- 2.30.2