From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 5634CCD4855 for ; Tue, 12 May 2026 07:15:35 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id B7D496B008C; Tue, 12 May 2026 03:15:34 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id B2E066B0092; Tue, 12 May 2026 03:15:34 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id A44516B0093; Tue, 12 May 2026 03:15:34 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0013.hostedemail.com [216.40.44.13]) by kanga.kvack.org (Postfix) with ESMTP id 93E2A6B008C for ; Tue, 12 May 2026 03:15:34 -0400 (EDT) Received: from smtpin08.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay09.hostedemail.com (Postfix) with ESMTP id 5676E8CAE4 for ; Tue, 12 May 2026 07:15:34 +0000 (UTC) X-FDA: 84757907388.08.ED6FAD6 Received: from mail.ilvokhin.com (mail.ilvokhin.com [178.62.254.231]) by imf13.hostedemail.com (Postfix) with ESMTP id 7A5732000E for ; Tue, 12 May 2026 07:15:32 +0000 (UTC) Authentication-Results: imf13.hostedemail.com; dkim=pass header.d=ilvokhin.com header.s=mail header.b=BZY3XNC+; dmarc=pass (policy=reject) header.from=ilvokhin.com; spf=pass (imf13.hostedemail.com: domain of d@ilvokhin.com designates 178.62.254.231 as permitted sender) smtp.mailfrom=d@ilvokhin.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1778570132; a=rsa-sha256; cv=none; b=B+uqIxEYJNP8uoGn2juzztYZjDa6LMG51y0BTW+jQx+pYcjnfZqwF4MPfBUl82k72ttxVH U6reb+gWJyJu4nNYN0Qwpd7S8MwuQEMFfuSrz2BGPsrzBjQboI0eZY6Ar7brachLnAbNVT bhz+lP4Hdqi/XqoCx2pebWj6Q8KxE3U= ARC-Authentication-Results: i=1; imf13.hostedemail.com; dkim=pass header.d=ilvokhin.com header.s=mail header.b=BZY3XNC+; dmarc=pass (policy=reject) header.from=ilvokhin.com; spf=pass (imf13.hostedemail.com: domain of d@ilvokhin.com designates 178.62.254.231 as permitted sender) smtp.mailfrom=d@ilvokhin.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1778570132; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-transfer-encoding:content-transfer-encoding: in-reply-to:references:dkim-signature; bh=BFor0KrBkxvS9w0H6iEW/kE3ciN1+oSXsC1h7srZquA=; b=s7yT4b6S2a9YjcfFQduVe3GrYWdawpfgKghi6XvGtW8tdwNldTfij20bFya/slVkw4BOac gFpWh4LJnmKMKcOPVfovrzIM0Bp+JcN36ynVgfD0UhMQnEZ/8Qgz1jrKlYMSZUgeKHmw6e q9y2EbzYsQZo15NTc2MnQRoh80LvDXA= Received: from localhost.localdomain (shell.ilvokhin.com [138.68.190.75]) (Authenticated sender: d@ilvokhin.com) by mail.ilvokhin.com (Postfix) with ESMTPSA id 9E93DD03F1; Tue, 12 May 2026 07:15:30 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ilvokhin.com; s=mail; t=1778570130; bh=BFor0KrBkxvS9w0H6iEW/kE3ciN1+oSXsC1h7srZquA=; h=From:To:Cc:Subject:Date; b=BZY3XNC+rtFbvH+ITtrgxA6DrZeIf4ChmwIoKFc78kqEg7hSrMs25mrS9VOyhTP/N YVgDeEkO0Rib71w4X0DLdGHCTE0POQWEYFHb3/ZiXRfmlAgMt3W8gR2MqTM6wjaa6o D55j8H1OwaL7YGNsr7uxzZ57bS6Wl1ShaMQ5OHc4= From: Dmitry Ilvokhin To: Peter Zijlstra , Christian Brauner , Dan Williams , Dave Jiang , Marco Elver , "H. Peter Anvin" , Andrew Morton Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, kernel-team@meta.com, Dmitry Ilvokhin Subject: [PATCH v2] cleanup: Remove NULL check from unconditional guards Date: Tue, 12 May 2026 07:15:10 +0000 Message-ID: <20260512071510.92451-1-d@ilvokhin.com> X-Mailer: git-send-email 2.54.0 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Stat-Signature: 1a9gqzt9zkcyc9bsfadje5dgzd3xqrqk X-Rspam-User: X-Rspamd-Queue-Id: 7A5732000E X-Rspamd-Server: rspam07 X-HE-Tag: 1778570132-612846 X-HE-Meta: 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 QT1fWOwC W5zSGcffveXZlqlZZS58BQTna2TKz6e4ilXrRmOVxC4yQHiiZo+4sa4USeJpb8vEm+oJidYbW5piCg4hWTSwC3VPY7sgKz+gr0nPaJMwlbpwwQhHeG8plZLCOJEX6lsvRELA7yVSKb4+92JXN2ilW/cX9btmVRRUr7kvQV6A6ovK6jG6wNxAlu7yV4tdU3g+XuB0iYAESg4XZNDDDtlqI3fs+lJE8shw6rC2TkS7impmOAfCB/PhSL4OMOUVY0bmZkdIkBWlaHsofVjA= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: The unconditional guard destructors check whether the lock pointer is NULL before unlocking. This check is dead code because unconditional guards guarantee a non-NULL lock pointer at destructor time. DEFINE_GUARD() and DEFINE_LOCK_GUARD_1() both run the lock operation in the constructor before returning. If the pointer were NULL, the lock operation (e.g. mutex_lock(NULL)) would crash before the constructor returns. The destructor never runs with a NULL pointer. DEFINE_LOCK_GUARD_0() hardcodes .lock = (void *)1 in the constructor, so it is never NULL by construction. Conditional (_try) variants: DEFINE_GUARD_COND() and DEFINE_LOCK_GUARD_1_COND() use EXTEND_CLASS_COND(), whose wrapper destructor returns early when the lock was not acquired, before reaching the base destructor since 2deccd5c862a ("cleanup: Optimize guards"): if (_cond) return; class_##_name##_destructor(_T); As compiled by GCC-11 with defconfig on top of the locking/core: Total: Before=23889980, After=23833993, chg -0.23% Signed-off-by: Dmitry Ilvokhin --- Changes in v2: - Expand commit message with detailed reasoning, why the proposed change is correct. - Rebase on top of locking/core. v1: https://lore.kernel.org/all/20260427165037.205337-1-d@ilvokhin.com/ See also [1] for relevant discussion. [1]: https://lore.kernel.org/all/afCS4d4YccQFtvpi@shell.ilvokhin.com/ include/linux/cleanup.h | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/include/linux/cleanup.h b/include/linux/cleanup.h index ea95ca4bc11c..1410effa8780 100644 --- a/include/linux/cleanup.h +++ b/include/linux/cleanup.h @@ -397,7 +397,7 @@ static __maybe_unused const bool class_##_name##_is_conditional = _is_cond __DEFINE_GUARD_LOCK_PTR(_name, _T) #define DEFINE_GUARD(_name, _type, _lock, _unlock) \ - DEFINE_CLASS(_name, _type, if (_T) { _unlock; }, ({ _lock; _T; }), _type _T); \ + DEFINE_CLASS(_name, _type, _unlock, ({ _lock; _T; }), _type _T); \ DEFINE_CLASS_IS_GUARD(_name) #define DEFINE_GUARD_COND_4(_name, _ext, _lock, _cond) \ @@ -491,7 +491,7 @@ typedef struct { \ static __always_inline void class_##_name##_destructor(class_##_name##_t *_T) \ __no_context_analysis \ { \ - if (_T->lock) { _unlock; } \ + _unlock; \ } \ \ __DEFINE_GUARD_LOCK_PTR(_name, &_T->lock) -- 2.53.0-Meta