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=-20.4 required=3.0 tests=BAYES_00,DKIMWL_WL_MED, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, USER_AGENT_GIT,USER_IN_DEF_DKIM_WL 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 188FDC388F9 for ; Tue, 27 Oct 2020 16:50:03 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id C227722202 for ; Tue, 27 Oct 2020 16:50:02 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="SGQLLWiB" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1813402AbgJ0QuA (ORCPT ); Tue, 27 Oct 2020 12:50:00 -0400 Received: from mail-pf1-f201.google.com ([209.85.210.201]:56178 "EHLO mail-pf1-f201.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1813387AbgJ0Qt4 (ORCPT ); Tue, 27 Oct 2020 12:49:56 -0400 Received: by mail-pf1-f201.google.com with SMTP id z12so1236574pfa.22 for ; Tue, 27 Oct 2020 09:49:56 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=sender:date:in-reply-to:message-id:mime-version:references:subject :from:to:cc; bh=nuxxs/Px/9QpRIlm7J+PyL0HWcASsbcWXqWCTDpjZLY=; b=SGQLLWiB+LUjaqR1TSdlpCpxrsi+POAiH2xjFLEZiQ/Wy8axJ7MQAwv6yJG4RQFjVH 2Bde6HUbl3/5tLJBqO2GGocfLTNhD4piiEGuFcTE3tNlCR/vOkEweNCcRo8i7U2fOu0+ UigavmfeQIAdOyfoCOq2wOlrR79bpk/B9bpd91hzS8apgFhVrwDZTlzlp/XoK5RIrc7U EgtcREjXUgluwLgZ/dBJ5fEwwxTQeMMERb5hdHFyDyg3jdX/f8TcLnKuVuBqHWDSO/Vf KMxOlowmn6ogA67Z+poRwIIIfbhDDnFdxm80hDvd3shtA5cXQWT1psAvvLBLUm4epcsX KbqQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:sender:date:in-reply-to:message-id:mime-version :references:subject:from:to:cc; bh=nuxxs/Px/9QpRIlm7J+PyL0HWcASsbcWXqWCTDpjZLY=; b=fKmZDW1FcbmHankkzPpMfkuI4i/VlE/z/YcGk5QDJdXIdHnygfsv8g3rDhzsOa8NLh 0QZVqgtJA5J14CjmEBWTabQ/3VD3grEJySzeoGBN8QHIaNjqGEb/Tgk/e37mKbK7M5QZ w5fpfSafRx6uVZmm9zKPhmToZW/gLXIe7F+ik6nWmqEokjENcLCVaiRno40Txc2dNLIx xMJe4dc2FU55J8IZ2IqAU7HEqszMVD7xqKdULMKU4kfeLh0MoqZwspUbdQ4vFxgnoqZd jcDvxNUTQQDHnrZH7fNQF5wKdyfiLZ1RjiEISbh2bB8xKY35Fhwl2Z6LEgU8a32CUo2b 6ohQ== X-Gm-Message-State: AOAM530+bycxUJcG7NQglh6GCeMp64KVx/Ui5/R+7eZFuSzKG0/LCGlV scvnHdgrWvmuVxCCIOMVvceZNcto37Rn X-Google-Smtp-Source: ABdhPJzT7GGtUaXKyrFhHPKMnptHgg3JCdWq1CQfBl6a05IhJ1AanAbFiyvdLmOm1ZktrH0sdKOH1g5fzZjb Sender: "bgardon via sendgmr" X-Received: from bgardon.sea.corp.google.com ([2620:15c:100:202:f693:9fff:fef4:a293]) (user=bgardon job=sendgmr) by 2002:a62:8097:0:b029:153:ce1d:c46 with SMTP id j145-20020a6280970000b0290153ce1d0c46mr3179460pfd.68.1603817395887; Tue, 27 Oct 2020 09:49:55 -0700 (PDT) Date: Tue, 27 Oct 2020 09:49:49 -0700 In-Reply-To: <20201027164950.1057601-1-bgardon@google.com> Message-Id: <20201027164950.1057601-2-bgardon@google.com> Mime-Version: 1.0 References: <20201027164950.1057601-1-bgardon@google.com> X-Mailer: git-send-email 2.29.0.rc2.309.g374f81d7ae-goog Subject: [PATCH 2/3] sched: Add needbreak for rwlocks From: Ben Gardon To: linux-kernel@vger.kernel.org, kvm@vger.kernel.org Cc: Paolo Bonzini , Sean Christopherson , Peter Shier , Peter Zijlstra , Ingo Molnar , Will Deacon , Waiman Long , Davidlohr Bueso , Ben Gardon Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org Contention awareness while holding a spin lock is essential for reducing latency when long running kernel operations can hold that lock. Add the same contention detection interface for read/write spin locks. Signed-off-by: Ben Gardon --- include/linux/sched.h | 17 +++++++++++++++++ 1 file changed, 17 insertions(+) diff --git a/include/linux/sched.h b/include/linux/sched.h index 063cd120b4593..77179160ec3ab 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -1870,6 +1870,23 @@ static inline int spin_needbreak(spinlock_t *lock) #endif } +/* + * Check if a rwlock is contended. + * Returns non-zero if there is another task waiting on the rwlock. + * Returns zero if the lock is not contended or the system / underlying + * rwlock implementation does not support contention detection. + * Technically does not depend on CONFIG_PREEMPTION, but a general need + * for low latency. + */ +static inline int rwlock_needbreak(rwlock_t *lock) +{ +#ifdef CONFIG_PREEMPTION + return rwlock_is_contended(lock); +#else + return 0; +#endif +} + static __always_inline bool need_resched(void) { return unlikely(tif_need_resched()); -- 2.29.0.rc2.309.g374f81d7ae-goog