From nobody Mon Feb 9 06:39:50 2026 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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 73ECAEE3F11 for ; Tue, 12 Sep 2023 19:55:20 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232767AbjILTzW (ORCPT ); Tue, 12 Sep 2023 15:55:22 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:53546 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229500AbjILTzU (ORCPT ); Tue, 12 Sep 2023 15:55:20 -0400 Received: from rere.qmqm.pl (rere.qmqm.pl [91.227.64.183]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 346451AE for ; Tue, 12 Sep 2023 12:55:16 -0700 (PDT) Received: from remote.user (localhost [127.0.0.1]) by rere.qmqm.pl (Postfix) with ESMTPSA id 4RlZ7P3vzrzB1; Tue, 12 Sep 2023 21:55:13 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=rere.qmqm.pl; s=1; t=1694548513; bh=hQNQ4QCGqogXkkq7quiXHYiRdH8sQiU3p2y0WgbusoQ=; h=Date:Subject:From:To:Cc:From; b=lmOpXkrUV529cwb3qYNI2wBT30mIicDUa0eryPCudafDE5DcDSGg7Pl7LZJKkkg3P bxtKM3jx+1RHManGMndEC38D4U2YC0ggtwHzyWNh7i0b0TfvixbA4A0dW/L3GF9jmb +UFIayaa1D1wuv4rAOzZ47jS7UUulgyTRNeOP1twtPedLUKdVhVo4QHwsAhsh3dzrH nI6kXLsy8Z9yZuGYGd4ITYm/i6F1JqGARRGax11k7x8nEDDgN1MwAT5W5GkSLYXpM3 ay78rKGbF5SPd9OPVF7T3rARuB6GeJXgF+RTtCpNaYhIwvniqBNNYIvmdSv5tT5u2x 5HxKrlP6gGoOQ== X-Virus-Status: Clean X-Virus-Scanned: clamav-milter 0.103.8 at mail Date: Tue, 12 Sep 2023 21:55:13 +0200 Message-Id: <13334f7016362b2031eb65b03cb1a49b6500957f.1694548262.git.mirq-linux@rere.qmqm.pl> Subject: [PATCH v3] locking/mutex: remove redundant argument from __mutex_lock_common() MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable From: =?UTF-8?q?Micha=C5=82=20Miros=C5=82aw?= To: Peter Zijlstra , Ingo Molnar , Will Deacon Cc: Waiman Long , Boqun Feng , linux-kernel@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org use_ww_ctx is equivalent to ww_ctx !=3D NULL. The one case where use_ww_ctx was true but ww_ctx =3D=3D NULL leads to the same __mutex_add_waiter() call via __ww_mutex_add_waiter(). Since now __ww_mutex_add_waiter() is called only with ww_mutex !=3D NULL (from both regular and PREEMPT_RT implementations), remove the branch there. Resulting object size diffs (by gcc-12) are minor: text data bss dec hex filename (x86-64) 22603 4696 16 27315 6ab3 /tmp/before.o 22593 4696 16 27305 6aa9 /tmp/after.o text data bss dec hex filename (arm) 13488 56 8 13552 34f0 /tmp/before.o 13492 56 8 13556 34f4 /tmp/after.o Signed-off-by: Micha=C5=82=C2=A0Miros=C5=82aw --- v3: extended commit message with `size` diffs + added back `if (ww_ctx)`-guarded store: compiler hoists it into the following branch anyway and so it avoids the unnecessary store in the `ww_ctx =3D=3D NULL` case. v2: extended commit message to note that PREEMPT_RT does not call __ww_mutex_add_waiter() with ww_ctx =3D=3D NULL --- kernel/locking/mutex.c | 15 ++++++--------- kernel/locking/ww_mutex.h | 5 ----- 2 files changed, 6 insertions(+), 14 deletions(-) diff --git a/kernel/locking/mutex.c b/kernel/locking/mutex.c index 4a3c006c41fb..045f7da4e473 100644 --- a/kernel/locking/mutex.c +++ b/kernel/locking/mutex.c @@ -578,15 +578,12 @@ EXPORT_SYMBOL(ww_mutex_unlock); static __always_inline int __sched __mutex_lock_common(struct mutex *lock, unsigned int state, unsigned int s= ubclass, struct lockdep_map *nest_lock, unsigned long ip, - struct ww_acquire_ctx *ww_ctx, const bool use_ww_ctx) + struct ww_acquire_ctx *ww_ctx) { struct mutex_waiter waiter; struct ww_mutex *ww; int ret; =20 - if (!use_ww_ctx) - ww_ctx =3D NULL; - might_sleep(); =20 MUTEX_WARN_ON(lock->magic !=3D lock); @@ -637,12 +634,12 @@ __mutex_lock_common(struct mutex *lock, unsigned int = state, unsigned int subclas =20 debug_mutex_lock_common(lock, &waiter); waiter.task =3D current; - if (use_ww_ctx) + if (ww_ctx) waiter.ww_ctx =3D ww_ctx; =20 lock_contended(&lock->dep_map, ip); =20 - if (!use_ww_ctx) { + if (!ww_ctx) { /* add waiting tasks to the end of the waitqueue (FIFO): */ __mutex_add_waiter(lock, &waiter, &lock->wait_list); } else { @@ -754,14 +751,14 @@ static int __sched __mutex_lock(struct mutex *lock, unsigned int state, unsigned int subclass, struct lockdep_map *nest_lock, unsigned long ip) { - return __mutex_lock_common(lock, state, subclass, nest_lock, ip, NULL, fa= lse); + return __mutex_lock_common(lock, state, subclass, nest_lock, ip, NULL); } =20 static int __sched __ww_mutex_lock(struct mutex *lock, unsigned int state, unsigned int subcl= ass, unsigned long ip, struct ww_acquire_ctx *ww_ctx) { - return __mutex_lock_common(lock, state, subclass, NULL, ip, ww_ctx, true); + return __mutex_lock_common(lock, state, subclass, NULL, ip, ww_ctx); } =20 /** @@ -841,7 +838,7 @@ mutex_lock_io_nested(struct mutex *lock, unsigned int s= ubclass) =20 token =3D io_schedule_prepare(); __mutex_lock_common(lock, TASK_UNINTERRUPTIBLE, - subclass, NULL, _RET_IP_, NULL, 0); + subclass, NULL, _RET_IP_, NULL); io_schedule_finish(token); } EXPORT_SYMBOL_GPL(mutex_lock_io_nested); diff --git a/kernel/locking/ww_mutex.h b/kernel/locking/ww_mutex.h index 3ad2cc4823e5..11acb2efe976 100644 --- a/kernel/locking/ww_mutex.h +++ b/kernel/locking/ww_mutex.h @@ -493,11 +493,6 @@ __ww_mutex_add_waiter(struct MUTEX_WAITER *waiter, struct MUTEX_WAITER *cur, *pos =3D NULL; bool is_wait_die; =20 - if (!ww_ctx) { - __ww_waiter_add(lock, waiter, NULL); - return 0; - } - is_wait_die =3D ww_ctx->is_wait_die; =20 /* --=20 2.39.2