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 X-Spam-Level: X-Spam-Status: No, score=-16.0 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id ABCA1C43381 for ; Tue, 16 Mar 2021 15:32:47 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 836D7650F0 for ; Tue, 16 Mar 2021 15:32:47 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232693AbhCPPcm (ORCPT ); Tue, 16 Mar 2021 11:32:42 -0400 Received: from us-smtp-delivery-124.mimecast.com ([63.128.21.124]:32591 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S237605AbhCPPcC (ORCPT ); Tue, 16 Mar 2021 11:32:02 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1615908721; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:in-reply-to:in-reply-to:references:references; bh=zDxX2w5rviLXmrv/FTW5VxRZx0k97vHoSbdhuH1WmcQ=; b=fxaqmHHHjAqIiSJHXz1zD2u5NXwyZ403Ytb0cqqpYT2liLS6a4SvfML26RD78AjgRUakke 24Ur8Z/Tp36E2GAPjkWNbAjXb+spZkBSQvSOfGlsBVxX/pk/6uxfCF4MfJEOrRvqMVrGeM SF2Mzns8tKtZ25HD/Yea84rp+wg+m1g= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-402-fPPHm70cNDmgxFinDKCFZg-1; Tue, 16 Mar 2021 11:32:00 -0400 X-MC-Unique: fPPHm70cNDmgxFinDKCFZg-1 Received: from smtp.corp.redhat.com (int-mx08.intmail.prod.int.phx2.redhat.com [10.5.11.23]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id AF1C1800C78; Tue, 16 Mar 2021 15:31:58 +0000 (UTC) Received: from llong.com (ovpn-117-133.rdu2.redhat.com [10.10.117.133]) by smtp.corp.redhat.com (Postfix) with ESMTP id 824C61A839; Tue, 16 Mar 2021 15:31:57 +0000 (UTC) From: Waiman Long To: Peter Zijlstra , Ingo Molnar , Will Deacon , Boqun Feng , "Paul E. McKenney" , Davidlohr Bueso Cc: linux-kernel@vger.kernel.org, Juri Lelli , Waiman Long Subject: [PATCH 1/4] locking/ww_mutex: Simplify use_ww_ctx & ww_ctx handling Date: Tue, 16 Mar 2021 11:31:16 -0400 Message-Id: <20210316153119.13802-2-longman@redhat.com> In-Reply-To: <20210316153119.13802-1-longman@redhat.com> References: <20210316153119.13802-1-longman@redhat.com> X-Scanned-By: MIMEDefang 2.84 on 10.5.11.23 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The use_ww_ctx flag is passed to mutex_optimistic_spin(), but the function doesn't use it. The frequent use of the (use_ww_ctx && ww_ctx) combination is repetitive. In fact, ww_ctx should not be used at all if !use_ww_ctx. Simplify ww_mutex code by dropping use_ww_ctx from mutex_optimistic_spin() an clear ww_ctx if !use_ww_ctx. In this way, we can replace (use_ww_ctx && ww_ctx) by just (ww_ctx). Signed-off-by: Waiman Long --- kernel/locking/mutex.c | 25 ++++++++++++++----------- 1 file changed, 14 insertions(+), 11 deletions(-) diff --git a/kernel/locking/mutex.c b/kernel/locking/mutex.c index adb935090768..622ebdfcd083 100644 --- a/kernel/locking/mutex.c +++ b/kernel/locking/mutex.c @@ -626,7 +626,7 @@ static inline int mutex_can_spin_on_owner(struct mutex *lock) */ static __always_inline bool mutex_optimistic_spin(struct mutex *lock, struct ww_acquire_ctx *ww_ctx, - const bool use_ww_ctx, struct mutex_waiter *waiter) + struct mutex_waiter *waiter) { if (!waiter) { /* @@ -702,7 +702,7 @@ mutex_optimistic_spin(struct mutex *lock, struct ww_acquire_ctx *ww_ctx, #else static __always_inline bool mutex_optimistic_spin(struct mutex *lock, struct ww_acquire_ctx *ww_ctx, - const bool use_ww_ctx, struct mutex_waiter *waiter) + struct mutex_waiter *waiter) { return false; } @@ -922,6 +922,9 @@ __mutex_lock_common(struct mutex *lock, long state, unsigned int subclass, struct ww_mutex *ww; int ret; + if (!use_ww_ctx) + ww_ctx = NULL; + might_sleep(); #ifdef CONFIG_DEBUG_MUTEXES @@ -929,7 +932,7 @@ __mutex_lock_common(struct mutex *lock, long state, unsigned int subclass, #endif ww = container_of(lock, struct ww_mutex, base); - if (use_ww_ctx && ww_ctx) { + if (ww_ctx) { if (unlikely(ww_ctx == READ_ONCE(ww->ctx))) return -EALREADY; @@ -946,10 +949,10 @@ __mutex_lock_common(struct mutex *lock, long state, unsigned int subclass, mutex_acquire_nest(&lock->dep_map, subclass, 0, nest_lock, ip); if (__mutex_trylock(lock) || - mutex_optimistic_spin(lock, ww_ctx, use_ww_ctx, NULL)) { + mutex_optimistic_spin(lock, ww_ctx, NULL)) { /* got the lock, yay! */ lock_acquired(&lock->dep_map, ip); - if (use_ww_ctx && ww_ctx) + if (ww_ctx) ww_mutex_set_context_fastpath(ww, ww_ctx); preempt_enable(); return 0; @@ -960,7 +963,7 @@ __mutex_lock_common(struct mutex *lock, long state, unsigned int subclass, * After waiting to acquire the wait_lock, try again. */ if (__mutex_trylock(lock)) { - if (use_ww_ctx && ww_ctx) + if (ww_ctx) __ww_mutex_check_waiters(lock, ww_ctx); goto skip_wait; @@ -1013,7 +1016,7 @@ __mutex_lock_common(struct mutex *lock, long state, unsigned int subclass, goto err; } - if (use_ww_ctx && ww_ctx) { + if (ww_ctx) { ret = __ww_mutex_check_kill(lock, &waiter, ww_ctx); if (ret) goto err; @@ -1026,7 +1029,7 @@ __mutex_lock_common(struct mutex *lock, long state, unsigned int subclass, * ww_mutex needs to always recheck its position since its waiter * list is not FIFO ordered. */ - if ((use_ww_ctx && ww_ctx) || !first) { + if (ww_ctx || !first) { first = __mutex_waiter_is_first(lock, &waiter); if (first) __mutex_set_flag(lock, MUTEX_FLAG_HANDOFF); @@ -1039,7 +1042,7 @@ __mutex_lock_common(struct mutex *lock, long state, unsigned int subclass, * or we must see its unlock and acquire. */ if (__mutex_trylock(lock) || - (first && mutex_optimistic_spin(lock, ww_ctx, use_ww_ctx, &waiter))) + (first && mutex_optimistic_spin(lock, ww_ctx, &waiter))) break; spin_lock(&lock->wait_lock); @@ -1048,7 +1051,7 @@ __mutex_lock_common(struct mutex *lock, long state, unsigned int subclass, acquired: __set_current_state(TASK_RUNNING); - if (use_ww_ctx && ww_ctx) { + if (ww_ctx) { /* * Wound-Wait; we stole the lock (!first_waiter), check the * waiters as anyone might want to wound us. @@ -1068,7 +1071,7 @@ __mutex_lock_common(struct mutex *lock, long state, unsigned int subclass, /* got the lock - cleanup and rejoice! */ lock_acquired(&lock->dep_map, ip); - if (use_ww_ctx && ww_ctx) + if (ww_ctx) ww_mutex_lock_acquired(ww, ww_ctx); spin_unlock(&lock->wait_lock); -- 2.18.1