From patchwork Sun Mar 8 18:05:27 2026 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Samuel Thibault X-Patchwork-Id: 131279 Return-Path: X-Original-To: patchwork@sourceware.org Delivered-To: patchwork@sourceware.org Received: from vm01.sourceware.org (localhost [127.0.0.1]) by sourceware.org (Postfix) with ESMTP id 7F02B4BA23F9 for ; Sun, 8 Mar 2026 18:05:59 +0000 (GMT) DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org 7F02B4BA23F9 X-Original-To: libc-alpha@sourceware.org Delivered-To: libc-alpha@sourceware.org Received: from sonata.ens-lyon.org (domu-toccata.ens-lyon.fr [140.77.166.138]) by sourceware.org (Postfix) with ESMTPS id CC25B4BA23C0 for ; Sun, 8 Mar 2026 18:05:30 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.2 sourceware.org CC25B4BA23C0 Authentication-Results: sourceware.org; dmarc=none (p=none dis=none) header.from=ens-lyon.org Authentication-Results: sourceware.org; spf=pass smtp.mailfrom=bounce.ens-lyon.org ARC-Filter: OpenARC Filter v1.0.0 sourceware.org CC25B4BA23C0 Authentication-Results: server2.sourceware.org; arc=none smtp.remote-ip=140.77.166.138 ARC-Seal: i=1; a=rsa-sha256; d=sourceware.org; s=key; t=1772993130; cv=none; b=F7ST+kjc9Eyy2e2Ta5NR5L7U1WfircaQBSzpDr7WB4dZmyYbdXC3X+kc8tauYvEYbs1QxJZ48VihfBUQ77y8ZDHFpGsEvdC348ZD2T+jeMf5qXZR7cgp7aoz/Pc8PJE+Lt4slWrwpOJgkTmu7ycmdJmD1ZiN7Oryhg3ry6582Nk= ARC-Message-Signature: i=1; a=rsa-sha256; d=sourceware.org; s=key; t=1772993130; c=relaxed/simple; bh=JonEP5S7OZzMD8+Q1NrBw2oH+/tjYqA7hAwJJDhqfcc=; h=From:To:Subject:Date:Message-ID:MIME-Version; b=uZ6M4eFiNSxgEaUWGgWejVxOcDm0oKiV/wJK1SfKwbW0bayLnek2JGzJT2AceiwE8hrcZPnBP4fHrE8OZ4+EdweDL6QYAbwVLrSaBtOg5i/rFD93XuL4dmSYKdzMQNg0feURsx34bj7YPrYBv0aZZrJ3Nq7HEpPWDCYVtJHhYYw= ARC-Authentication-Results: i=1; server2.sourceware.org DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org CC25B4BA23C0 Received: from localhost (localhost [127.0.0.1]) by sonata.ens-lyon.org (Postfix) with ESMTP id AE89CA0267; Sun, 8 Mar 2026 19:05:29 +0100 (CET) Received: from sonata.ens-lyon.org ([127.0.0.1]) by localhost (sonata.ens-lyon.org [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id VDRrqkQ6NCu3; Sun, 8 Mar 2026 19:05:29 +0100 (CET) Received: from end (aamiens-653-1-40-48.w83-192.abo.wanadoo.fr [83.192.199.48]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange ECDHE (P-256) server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) by sonata.ens-lyon.org (Postfix) with ESMTPSA id 78541A024D; Sun, 8 Mar 2026 19:05:29 +0100 (CET) Received: from samy by end with local (Exim 4.99.1) (envelope-from ) id 1vzIVN-0000000GQKk-06SX; Sun, 08 Mar 2026 19:05:29 +0100 From: Samuel Thibault To: libc-alpha@sourceware.org Cc: Samuel Thibault , commit-hurd@gnu.org, Brent Baccala Subject: [hurd,commited] htl: Fix pthread_once memory ordering Date: Sun, 8 Mar 2026 19:05:27 +0100 Message-ID: <20260308180527.3914466-1-samuel.thibault@ens-lyon.org> X-Mailer: git-send-email 2.51.0 MIME-Version: 1.0 X-Spam-Status: No, score=-12.1 required=5.0 tests=BAYES_00, GIT_PATCH_0, JMQ_SPF_NEUTRAL, KAM_DMARC_STATUS, RCVD_IN_DNSWL_BLOCKED, RCVD_IN_VALIDITY_RPBL_BLOCKED, RCVD_IN_VALIDITY_SAFE_BLOCKED, SPF_HELO_PASS, SPF_PASS, TXREP autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on sourceware.org X-BeenThere: libc-alpha@sourceware.org X-Mailman-Version: 2.1.30 Precedence: list List-Id: Libc-alpha mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: libc-alpha-bounces~patchwork=sourceware.org@sourceware.org We need to tie the fast-path read with the store, to make sure that when fast-reading 1, we see all the effects performed by the init routine. (and we don't need a full barrier, only an acquire/release pair is needed) Reported-by: Brent Baccala 's Claude assistant --- sysdeps/htl/pt-once.c | 6 ++---- 1 file changed, 2 insertions(+), 4 deletions(-) diff --git a/sysdeps/htl/pt-once.c b/sysdeps/htl/pt-once.c index 5737033bf7..965ab8894c 100644 --- a/sysdeps/htl/pt-once.c +++ b/sysdeps/htl/pt-once.c @@ -34,8 +34,7 @@ __pthread_once (pthread_once_t *once_control, void (*init_routine) (void)) { ASSERT_TYPE_SIZE (pthread_once_t, __SIZEOF_PTHREAD_ONCE_T); - atomic_full_barrier (); - if (once_control->__run == 0) + if (atomic_load_acquire (&once_control->__run) == 0) { __pthread_spin_wait (&once_control->__lock); @@ -45,8 +44,7 @@ __pthread_once (pthread_once_t *once_control, void (*init_routine) (void)) init_routine (); pthread_cleanup_pop (0); - atomic_full_barrier (); - once_control->__run = 1; + atomic_store_release (&once_control->__run, 1); } __pthread_spin_unlock (&once_control->__lock);