From nobody Sat Oct 31 10:06:33 2026 X-Original-To: dev-commits-src-branches@mlmmj.nyi.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2610:1c1:1:606c::19:1]) by mlmmj.nyi.freebsd.org (Postfix) with ESMTP id 4jGtsk3H9qz6yLKC for ; Sat, 31 Oct 2026 10:06:34 +0000 (UTC) (envelope-from git@FreeBSD.org) Received: from mxrelay.nyi.freebsd.org (mxrelay.nyi.freebsd.org [IPv6:2610:1c1:1:606c::19:3]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange x25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) by mx1.freebsd.org (Postfix) with ESMTPS id 4jGtsj6TpHz4cgk for ; Sat, 31 Oct 2026 10:06:33 +0000 (UTC) (envelope-from git@FreeBSD.org) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=freebsd.org; s=dkim; t=1793441193; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding; bh=3HxheaH2oxbLXwuVC06U5/1qUsPS2JqEwCCvDTKErlM=; b=v9BcTt3qhoROvDWte43naaeeU2f+/bDvtmtS7KQkn+LDVuxlNKKqoyGTZWaPLelXtiIExr irSSyFgeMwV0Vl37qZ8yYZ/DDggJKiWQ92edDAaxuOBmf2jKT5UqT/b2vsQEs0RdWNHz3L dtvFMPl89dlFKDoHIOC6Y2Pkbuu++X1ml9e+pKOnOPRUaslGeC4Q60yOeHusUmWRmZRses 7gxYsCZm/K95e6cnXaAtvOmUqKAQ8hDWJBPiz+XO3aM06ObanJw0bLy6dpauV6enoxNL3K 60zdUa2mWf3sTa/KHftJV1HXGuyMusTh3IhzqAFwEQiR+I2liz1W5VQ+BF8x6A== ARC-Seal: i=1; a=rsa-sha256; d=freebsd.org; s=dkim; cv=none; t=1793441193; b=GqDVtQRulNtp66N8G21oo0TT954c3zw87ANP8/wOMF33fUIKzVfOzbe5DWjFlg9YSfFm/3 1y+fjfgi0OM4CZvFEdZwyZFO0ZgIUBj4j+t9fWftny2T44/kMG6EAeO338dsjDSVcpBVcH I3VRnuChFHJWzIL/GrCB5fLx5lsNub5DT2EzzBWts5N2VBnNI24uZWxn9U9HMfaBJAcLJg jQIvDt0ueNXu+i/WrHR/jeNmvHyGPsncp6xE7tNfepP8m5mXAJRFZKx+ooaHf7cj/Z93N0 H+gAMC/R5bNnVk3iByVeMwpg/6urB6vbC95DtGyp1ASnEpbAr/DEsrXxF5BNKg== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=freebsd.org; s=dkim; t=1793441193; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding; bh=3HxheaH2oxbLXwuVC06U5/1qUsPS2JqEwCCvDTKErlM=; b=UAHvgg1Fo2o9g0BgSI+wgaH56gokKKdBmjCMw7Gk3cwzMkDIR3/DtBHMdvaF57YamZJVm3 7OtD1hPBrM1R2IRWF5q1kUkmOFyunENEFjNKdecM9bOLu0jz4J77veF8ssS3FgTOVyPyXJ PsMEs04dH9kmKFWOK3ro1PmbJdVfDzCtUlHc0CzRKL6ZvTe2BcI+sAXjJh7ZVvDVDZ8ovA Dy1IAZV3VSI5+jxI4I2RH3xojU+7XJOgjJ1tn9g3jbm/yafKvYsPcq6U/oHsUu4b7nMhE5 fuo8T3rwhS95GJQnRCfzVxtSSQ1lIB++T0YuphdFFt8n8sG0AV7xCgOeWP5zlA== ARC-Authentication-Results: i=1; mx1.freebsd.org; none Received: from gitrepo.freebsd.org (gitrepo.freebsd.org [IPv6:2610:1c1:1:6068::e6a:5]) by mxrelay.nyi.freebsd.org (Postfix) with ESMTP id 4jGtsj58d4z18Rr for ; Sat, 31 Oct 2026 10:06:33 +0000 (UTC) (envelope-from git@FreeBSD.org) Received: from git (uid 1279) (envelope-from git@FreeBSD.org) id 3b52c by gitrepo.freebsd.org (DragonFly Mail Agent v0.13+ on gitrepo.freebsd.org); Sat, 31 Oct 2026 10:06:33 +0000 To: src-committers@FreeBSD.org, dev-commits-src-all@FreeBSD.org, dev-commits-src-branches@FreeBSD.org Cc: Faraz Vahedi From: Faraz Vahedi Subject: git: 53ba20bad789 - stable/15 - libc: Enforce lock-free atomic_flag and C23-safe initialisation List-Archive: https://lists.freebsd.org/archives/dev-commits-src-branches X-BeenThere: dev-commits-src-branches@freebsd.org Sender: owner-dev-commits-src-branches@FreeBSD.org List-Id: Commits to the stable branches of the FreeBSD src repository List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit X-Git-Committer: kfv X-Git-Repository: src X-Git-Refname: refs/heads/stable/15 X-Git-Reftype: branch X-Git-Commit: 53ba20bad7895e3c504856ac9b94f91655de6480 Auto-Submitted: auto-generated Date: Sat, 31 Oct 2026 10:06:33 +0000 Message-Id: <6ae5bda9.3b52c.15e08b15@gitrepo.freebsd.org> The branch stable/15 has been updated by kfv: URL: https://cgit.FreeBSD.org/src/commit/?id=53ba20bad7895e3c504856ac9b94f91655de6480 commit 53ba20bad7895e3c504856ac9b94f91655de6480 Author: Faraz Vahedi AuthorDate: 2026-05-07 10:25:56 +0000 Commit: Faraz Vahedi CommitDate: 2026-10-31 10:03:31 +0000 libc: Enforce lock-free atomic_flag and C23-safe initialisation Select the `atomic_flag` backing type according to the C standard requirements that `atomic_flag` operations be lock-free. C11 §7.17.1.5 defines `atomic_flag` as: > a structure type representing a lock-free, primitive atomic flag and §7.17.8.2 further requires: > Operations on an object of type atomic_flag shall be lock free Therefore: - Prefer `atomic_bool` when `ATOMIC_BOOL_LOCK_FREE == 2` - Fall back to `atomic_uchar` when `ATOMIC_CHAR_LOCK_FREE == 2` - Trigger a translation failure if neither type is lock-free Adjust `ATOMIC_FLAG_INIT` for C23 initialisation rules: - Use `{ ATOMIC_VAR_INIT(0) }` in pre-C23 modes - Use `{ 0 }` in C23 and later Preserve `atomic_flag_test_and_set_explicit()` semantics by normalising the exchanged value with `!= 0`, ensuring consistent boolean results regardless of whether the underlying representation is `atomic_bool` or `atomic_uchar`. Signed-off-by: Faraz Vahedi Reviewed by: imp Pull Request: https://github.com/freebsd/freebsd-src/pull/2185 (cherry picked from commit 640ddf8571291ab2965de85f67e6065a4d7efbf8) --- sys/sys/stdatomic.h | 16 ++++++++++++---- 1 file changed, 12 insertions(+), 4 deletions(-) diff --git a/sys/sys/stdatomic.h b/sys/sys/stdatomic.h index bbdd196515e0..3e4bdd505418 100644 --- a/sys/sys/stdatomic.h +++ b/sys/sys/stdatomic.h @@ -377,21 +377,29 @@ __extension__ ({ \ /* * 7.17.8 Atomic flag type and operations. - * - * XXX: Assume atomic_bool can be used as an atomic_flag. Is there some - * kind of compiler built-in type we could use? */ typedef struct { +#if ATOMIC_BOOL_LOCK_FREE == 2 atomic_bool __flag; +#elif ATOMIC_CHAR_LOCK_FREE == 2 + atomic_uchar __flag; +#else +#error "atomic_flag is required to be lock-free" +#endif } atomic_flag; +#if __ISO_C_VISIBLE < 2023 #define ATOMIC_FLAG_INIT { ATOMIC_VAR_INIT(0) } +#else +#define ATOMIC_FLAG_INIT { 0 } +#endif static __inline _Bool atomic_flag_test_and_set_explicit(volatile atomic_flag *__object, memory_order __order) { - return (atomic_exchange_explicit(&__object->__flag, 1, __order)); + + return (atomic_exchange_explicit(&__object->__flag, 1, __order) != 0); } static __inline void