From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from rock.gnat.com (rock.gnat.com [205.232.38.15]) by sourceware.org (Postfix) with ESMTPS id E39C2383542E for ; Wed, 30 Jun 2021 09:30:48 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.1 sourceware.org E39C2383542E Authentication-Results: sourceware.org; dmarc=none (p=none dis=none) header.from=adacore.com Authentication-Results: sourceware.org; spf=pass smtp.mailfrom=adacore.com Received: from localhost (localhost.localdomain [127.0.0.1]) by filtered-rock.gnat.com (Postfix) with ESMTP id 09992116CB8 for ; Wed, 30 Jun 2021 05:30:46 -0400 (EDT) X-Virus-Scanned: Debian amavisd-new at gnat.com Received: from rock.gnat.com ([127.0.0.1]) by localhost (rock.gnat.com [127.0.0.1]) (amavisd-new, port 10024) with LMTP id m+RA83j7DMva for ; Wed, 30 Jun 2021 05:30:45 -0400 (EDT) Received: from tron.gnat.com (tron.gnat.com [205.232.38.10]) by rock.gnat.com (Postfix) with ESMTP id ED1EB116CD7 for ; Wed, 30 Jun 2021 05:30:45 -0400 (EDT) Received: by tron.gnat.com (Postfix, from userid 4862) id EC6381E7; Wed, 30 Jun 2021 05:30:45 -0400 (EDT) Date: Wed, 30 Jun 2021 05:30:45 -0400 From: Pierre-Marie de Rodat To: gcc-patches@gcc.gnu.org Subject: [Ada] Ensure System.Tasking.Debug.Known_Tasks component access is atomic Message-ID: <20210630093045.GA1744@adacore.com> MIME-Version: 1.0 Content-Type: multipart/mixed; boundary="envbJBWh7q8WU6mo" Content-Disposition: inline User-Agent: Mutt/1.5.23 (2014-03-12) X-Spam-Status: No, score=-12.7 required=5.0 tests=BAYES_00, GIT_PATCH_0, KAM_DMARC_STATUS, SPF_HELO_NONE, SPF_PASS, TXREP autolearn=ham autolearn_force=no version=3.4.2 X-Spam-Checker-Version: SpamAssassin 3.4.2 (2018-09-13) on server2.sourceware.org X-BeenThere: gcc-patches@gcc.gnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Gcc-patches mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 30 Jun 2021 09:30:51 -0000 --envbJBWh7q8WU6mo Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Multiple threads can access the elements of System.Tasking.Debug.Known_Tasks concurrently. While the compiler will generally produce code that reads and writes Task_Ids atomically since Task_Id is word size, it is best to be explicit to prevent data race issues that may arise from non-atomic component accesses. Tested on x86_64-pc-linux-gnu, committed on trunk gcc/ada/ * libgnarl/s-tasdeb.ads (Known_Tasks): Add Atomic_Components aspect. --envbJBWh7q8WU6mo Content-Type: text/x-diff; charset=us-ascii Content-Disposition: attachment; filename="patch.diff" diff --git a/gcc/ada/libgnarl/s-tasdeb.ads b/gcc/ada/libgnarl/s-tasdeb.ads --- a/gcc/ada/libgnarl/s-tasdeb.ads +++ b/gcc/ada/libgnarl/s-tasdeb.ads @@ -65,9 +65,11 @@ package System.Tasking.Debug is -- General GDB support -- ------------------------- - Known_Tasks : array (0 .. 999) of Task_Id := (others => null); + Known_Tasks : array (0 .. 999) of Task_Id := (others => null) + with Atomic_Components; -- Global array of tasks read by gdb, and updated by Create_Task and - -- Finalize_TCB + -- Finalize_TCB. Ensure access to its components is atomic to allow + -- lock-free concurrent access. Debug_Event_Activating : constant := 1; Debug_Event_Run : constant := 2; --envbJBWh7q8WU6mo--