From patchwork Tue Jan 12 18:10:19 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Ben Gardon X-Patchwork-Id: 12014297 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=-26.3 required=3.0 tests=BAYES_00,DKIMWL_WL_MED, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,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 80692C433E9 for ; Tue, 12 Jan 2021 18:11:55 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 5762D2311F for ; Tue, 12 Jan 2021 18:11:55 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2392041AbhALSLm (ORCPT ); Tue, 12 Jan 2021 13:11:42 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:56712 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729128AbhALSLl (ORCPT ); Tue, 12 Jan 2021 13:11:41 -0500 Received: from mail-yb1-xb4a.google.com (mail-yb1-xb4a.google.com [IPv6:2607:f8b0:4864:20::b4a]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id D8A43C0617A2 for ; Tue, 12 Jan 2021 10:10:49 -0800 (PST) Received: by mail-yb1-xb4a.google.com with SMTP id e137so3284283ybf.16 for ; Tue, 12 Jan 2021 10:10:49 -0800 (PST) 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=C9vIvaeT5TM0OnnRWqYO7mCFVABYsaJZT2qRGhHXbMM=; b=PV4b8+Nqu6dTrIei2IlEQ8qMMwyHUaAfdM4cHfMSVk7ceox8oaA9sz1MT7qsRERRrS s8Z1xt/1cXjtB5b+T3Wg5QS6mvjtRuMyNRTXQsMKQNuUpaFJCPc9UXyiQ+d5FQ1ZzZzW XCbpYb+Uu2IJ8br9EyU/EeuStUPvmfpuho743wszk5A3YfE1WpRE7SOEM0+wJGRgifgL Lbba2kvdlU5qJJFChaE3n0dH6cHGxdPL2kaEt9icaX7RW1AMH4TVILv3ScM3CciQy2tu MTpcErkxRpRsi2nBHRxBoqPKZkWbf1uKdVMP4V7LaPi2SKOYNr/jX6WREK39V2EHtVyZ kO1Q== 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=C9vIvaeT5TM0OnnRWqYO7mCFVABYsaJZT2qRGhHXbMM=; b=Qzr8Pab5V+ekSIjWUhZ0fn4kZheeY2qt/anEnQr+M3ygvv+2HhOY5eYowBZZ2CFf6R uT0gwon0v+pB0meZSbkl7ut6BOthzQ9sKLEJWd5xTU93ZNpJKwE0BWNtQWQ1ShIrR2mN R4ivmbF0DC6I+MPjEZzvVh4T/jS0aqSw5rtCQ2Alh8OAlsiuFbbrQihlVeFrvl9WrXb5 5qjuH53j2gHo5M4m04X6RULDOipztZyjqVSmVDiyl1upszpkx15AGkd5KdwWkoLIzpN7 nn2Qqlfwch6OXeaqVtbeum16U4UYniFnivyivgL6CYRbbrO/o5IDu4dH45Moxe43I46N qthw== X-Gm-Message-State: AOAM533ih9BzXFTuqyGfrAp/k4odLRupzLP0qBDU1cNo2FZw1LhNpgXX VkHgLUkDylNEq5/YdDGF8YVH//plJbKB X-Google-Smtp-Source: ABdhPJywC7dNSUcRIcAleDfsH3vsuteOm8Tk1648RI634RDVUCm7jUNUWjmo6tdiqtjCz24UnHzMPywAXz/m 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:a25:d1c4:: with SMTP id i187mr929762ybg.7.1610475049081; Tue, 12 Jan 2021 10:10:49 -0800 (PST) Date: Tue, 12 Jan 2021 10:10:19 -0800 In-Reply-To: <20210112181041.356734-1-bgardon@google.com> Message-Id: <20210112181041.356734-3-bgardon@google.com> Mime-Version: 1.0 References: <20210112181041.356734-1-bgardon@google.com> X-Mailer: git-send-email 2.30.0.284.gd98b1dd5eaa7-goog Subject: [PATCH 02/24] sched: Add needbreak for rwlocks From: Ben Gardon To: linux-kernel@vger.kernel.org, kvm@vger.kernel.org Cc: Paolo Bonzini , Peter Xu , Sean Christopherson , Peter Shier , Peter Feiner , Junaid Shahid , Jim Mattson , Yulei Zhang , Wanpeng Li , Vitaly Kuznetsov , Xiao Guangrong , Ben Gardon , Ingo Molnar , Will Deacon , Peter Zijlstra , Davidlohr Bueso , Waiman Long 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. CC: Ingo Molnar CC: Will Deacon Acked-by: Peter Zijlstra Acked-by: Davidlohr Bueso Acked-by: Waiman Long Acked-by: Paolo Bonzini 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 6e3a5eeec509..5d1378e5a040 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -1912,6 +1912,23 @@ 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());