From nobody Sat Jun 20 00:24:55 2026 X-Original-To: dev-commits-src-main@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 4ghwG11Hqmz6hFJh for ; Sat, 20 Jun 2026 00:24:57 +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 client-signature RSA-PSS (4096 bits) client-digest SHA256) (Client CN "mxrelay.nyi.freebsd.org", Issuer "YR1" (not verified)) by mx1.freebsd.org (Postfix) with ESMTPS id 4ghwG01NWSz3J0P for ; Sat, 20 Jun 2026 00:24:56 +0000 (UTC) (envelope-from git@FreeBSD.org) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=freebsd.org; s=dkim; t=1781915096; 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=fbi5PV/U9RektkKEpSGiF8GlNkruOYypc6Q1BIHY7NM=; b=TxngLYJttwGO7s0COZaaSVQcuAkGGVAkub1vCoW0RAMUzeGv5CCydlinflRSbHYL3hBJpL 6poUcFnf+K0hv7tPGWscEt5HY4h57BIbcC1fBqSKR7nWefxdBLmniVgB8sCKK4QCrktNMu XxyiGKD4bki0Rrg9U1nit2hpUhBtZemPU4ScV7ZmUvyhmz6ArttannKKGlmw8E+M+7ImnI SBgTfeuIT08Fss3OXBk13GOkPdn8i+yau4Bh4JRIwpnNDR4xepRD7IEdkHVusB2DTksdKy bm5e8ri5GrvGsqzdNuyQlGImyLhYJQT/5/QjVgqMqYyM49+4Dzmw8ReBQutEcQ== ARC-Seal: i=1; s=dkim; d=freebsd.org; t=1781915096; a=rsa-sha256; cv=none; b=AdMFr67L2yzMcQ4H10N4qWzjcVlFfI/P9sRLFuHwxvnY3luFF+VEKpaCSq3WZKfbOU5YMA TD5LpSf3fRzhkahZFU9vCPnbPlvhtku5YWZ7x38NhJKqPazz6GRqCpuThpJI0vbPzeYw2r mxhc2eeOfw5QNVF1qsjaWRiUgVED2oJ6uMQXMlUBzP/fY4ZIMcPhwR1xBgT9S9tc+ZzLdq 6oRujXc4Sffom1n/hnk/BRp/Xqu87as5qClnKXvYQqMTg3xtAphgsl2NKSRZ124SA4uUvk OAZf47IEQEPMnkpCIacHZFa/1DwKWauvUVWyaF1UM/gMZevPohEdEXDgKx+kTQ== ARC-Authentication-Results: i=1; mx1.freebsd.org; none ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=freebsd.org; s=dkim; t=1781915096; 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=fbi5PV/U9RektkKEpSGiF8GlNkruOYypc6Q1BIHY7NM=; b=x2Z2CXQB8iJRRZBSZ9lyNu+lpb//q0u9xGMNAwhJHzVLDBKXTxTnaT5dS5vrxASArChfTS 0vaCwfEVvtRdT0PCbYaJVwaBICffM/LPnxobEluIpOsw8dz3km1EeXXtHr7aDsvZlliYN0 g7WerFers6Qe2fEC/2MJGmkpva8be4xuk6SU4UiKikxCj1SxckHpSERVdw33JTPI+JNQ8n wk6jWENOsHkoCh24Y69W5C+xwB3mSxTfWahfAFeHi9Ik0TXHMacHEVL/Bti1o2MK0NwlTv GadvzQ1rrOcLpI4HPdQCjQfMO94XM34bnLqlvSnIYQuaP0L5TIJEsASzVhlrZA== Received: from gitrepo.freebsd.org (gitrepo.freebsd.org [IPv6:2610:1c1:1:6068::e6a:5]) by mxrelay.nyi.freebsd.org (Postfix) with ESMTP id 4ghwFz70pdz1739 for ; Sat, 20 Jun 2026 00:24:55 +0000 (UTC) (envelope-from git@FreeBSD.org) Received: from git (uid 1279) (envelope-from git@FreeBSD.org) id 25928 by gitrepo.freebsd.org (DragonFly Mail Agent v0.13+ on gitrepo.freebsd.org); Sat, 20 Jun 2026 00:24:55 +0000 To: src-committers@FreeBSD.org, dev-commits-src-all@FreeBSD.org, dev-commits-src-main@FreeBSD.org Cc: Faraz Vahedi From: Warner Losh Subject: git: 640ddf857129 - main - libc: Enforce lock-free atomic_flag and C23-safe initialisation List-Id: Commit messages for the main branch of the src repository List-Archive: https://lists.freebsd.org/archives/dev-commits-src-main List-Help: List-Post: List-Subscribe: List-Unsubscribe: X-BeenThere: dev-commits-src-main@freebsd.org Sender: owner-dev-commits-src-main@FreeBSD.org List-Id: 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: imp X-Git-Repository: src X-Git-Refname: refs/heads/main X-Git-Reftype: branch X-Git-Commit: 640ddf8571291ab2965de85f67e6065a4d7efbf8 Auto-Submitted: auto-generated Date: Sat, 20 Jun 2026 00:24:55 +0000 Message-Id: <6a35ddd7.25928.6937188a@gitrepo.freebsd.org> The branch main has been updated by imp: URL: https://cgit.FreeBSD.org/src/commit/?id=640ddf8571291ab2965de85f67e6065a4d7efbf8 commit 640ddf8571291ab2965de85f67e6065a4d7efbf8 Author: Faraz Vahedi AuthorDate: 2026-05-07 10:25:56 +0000 Commit: Warner Losh CommitDate: 2026-06-20 00:23:29 +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 --- 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