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=-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=unavailable 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 6BBEAC433E6 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 40E2722DFA for ; Tue, 12 Jan 2021 18:11:55 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2392158AbhALSLm (ORCPT ); Tue, 12 Jan 2021 13:11:42 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:56714 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2391891AbhALSLl (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 F3E4BC0617A3 for ; Tue, 12 Jan 2021 10:10:49 -0800 (PST) Received: by mail-yb1-xb4a.google.com with SMTP id g17so3276690ybh.5 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=F2ORJoWxFzacAlAXGcGOvMvgZtNLwJVWL8/Go4FWRmwCJ/Wgs5XSoiiSbk9tYqgx23 Ts/cOWyiwqne6xKG8YfEGm1CoAKw/i/IauXCjGqsB4rkUiPOt7RHqeDupa58PrPwzFhU wibaSmFxWYgAfE/n3bSpEO1Se1VwMsyE0X/JuaKyo5DE06a4AsiihCr3sl4TdNr1/LWn U4fcCOmCrmhMbzlyhJZaeQ6634qSvCnZvtW3En3saJ6CMtpii6kVg7BCaEsKvq/lNQL/ 6fmY/uL/zWnr+FUTRtlFRfrFRrIwD9L/SQMYTXmc4fDghssh/Iowal/I/wH33gIxJnRz Ze6g== X-Gm-Message-State: AOAM5306yDl9mXQO1LW6NQHyLtpkEELvV+FA1NFBq1SrYXGBo2O1Z9hh GmXOGPuQx+CYyke0Vi90PKcaZuAps91vQl4tTZcP2hPc8lqUvrUJbFRItUy7IoVJM7USgj353Yf p2Q0ywYdvADs5VlPVtPXH59rQi8s7fvkidib1DX/0nhZ2U37XFgMtWxlQ2WpHaqwgWYoNqU3M 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 Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@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()); -- 2.30.0.284.gd98b1dd5eaa7-goog