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, 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 B5166C433C1 for ; Mon, 22 Mar 2021 18:44:31 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 7B2A6619A0 for ; Mon, 22 Mar 2021 18:44:31 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231405AbhCVSoD (ORCPT ); Mon, 22 Mar 2021 14:44:03 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:47984 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231253AbhCVSnf (ORCPT ); Mon, 22 Mar 2021 14:43:35 -0400 Received: from mail-qt1-x84a.google.com (mail-qt1-x84a.google.com [IPv6:2607:f8b0:4864:20::84a]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 95CC5C061574 for ; Mon, 22 Mar 2021 11:43:34 -0700 (PDT) Received: by mail-qt1-x84a.google.com with SMTP id b21so32419887qtr.8 for ; Mon, 22 Mar 2021 11:43:34 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=date:in-reply-to:message-id:mime-version:references:subject:from:to :cc; bh=zNDWMRbtqgU+iwXs/7K3ehA/M7zAKlzAJTVv5nnU03o=; b=Q8C7exskqqdhqLS56Dtj9+CObLS82y20GOHSZs6XEmEErMwwFH07899rU9f2wBrkQj uk171nhed4wl+uKppPNFpAPhRfLIwdj0QqWVI3vkZkmfpkwb0eBCye66/KWxJzghbSj1 TWa3EvQSKs+ukvkNA0HBITlYQwEDxspD/T6gqQfy8SWhwfM/73G39LD4HzW5Mw9h9l/y LCVy3qKauK8nOjM+j4dtKtVK9GdhsDz2wRJaWEzTajvASJKiYnZF3lxaNaRwygzXJKQY TJGiG9Sh0JrNKFvvg7SedQlL1ZNFrm0sqMM8dENH8OCGKXM4FGIu4OMIFZm8yOLGOhS6 RUeA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:in-reply-to:message-id:mime-version :references:subject:from:to:cc; bh=zNDWMRbtqgU+iwXs/7K3ehA/M7zAKlzAJTVv5nnU03o=; b=XK6i8JS0H1oHmeKJFAOCioiWnWE04sisneRJUErB1ZQtfasQAfE3TtIohEQ/W6CyBH qy+rKQsBvoOS2ovprWFFpCGth594GjrgetY6YJM3AxCNPoXdX1Gy+l4LgO3qFZrHttqy eWvYyj9Ol3YfZoQyLjer17LG6ILR3NhxIM7IZNbdsoq0QBgnPywKfWIX/vPZfpNeu+FB Nu9+aMokgv8n2vpYb5w6LTLUCI0EungLQe7gLjfSW9VXRFG3SmjBrCi8WbzG+20072Qd b5zKRqvFvb9zjbG+hWMUZDsK0DV0hsXX/fUJcnYY3qy1n7QzLNyndyilEplMFRi/+PJR G68A== X-Gm-Message-State: AOAM53184nkWJ7FsrMM3tTi87wIKGOLfABZm10VE5Ku8hW9vf2M71CLC aLZ+E9Y5fY/RybdjY945inD9MTli X-Google-Smtp-Source: ABdhPJzLqHXD7iG5PlIToHwO75qUPbROHrLSc6h6IIjcXF5UppPAWSVGFkJL4v9eAOYWJN5u3BxPH6YH X-Received: from gnomeregan.cam.corp.google.com ([2620:15c:6:412:ec52:3eae:f873:1de1]) (user=brho job=sendgmr) by 2002:a0c:a99a:: with SMTP id a26mr1093670qvb.2.1616438613767; Mon, 22 Mar 2021 11:43:33 -0700 (PDT) Date: Mon, 22 Mar 2021 14:43:24 -0400 In-Reply-To: Message-Id: <20210322184324.437430-1-brho@google.com> Mime-Version: 1.0 References: X-Mailer: git-send-email 2.31.0.rc2.261.g7f71774620-goog Subject: [PATCH v2] sched: allow resubmits to queue_balance_callback() From: Barret Rhoden To: Ingo Molnar , Peter Zijlstra , Juri Lelli , Vincent Guittot Cc: Dietmar Eggemann , Steven Rostedt , Ben Segall , Mel Gorman , Daniel Bristot de Oliveira , linux-kernel@vger.kernel.org Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Prior to this commit, if you submitted the same callback_head twice, it would be enqueued twice, but only if it was the last callback on the list. The first time it was submitted, rq->balance_callback was NULL, so head->next is NULL. That defeated the check in queue_balance_callback(). This commit changes the callback list such that whenever an item is on the list, its head->next is not NULL. The last element (first inserted) will point to itself. This allows us to detect and ignore any attempt to reenqueue a callback_head. Signed-off-by: Barret Rhoden --- sorry about the old version. i updated to linus's branch, plus a minor fix from v1. this should work with the balance_push_callback stuff you added a few months ago. in this commit, head->next can equal null *or* head and it will be treated as null. (balance_push_callback's next == NULL). thanks, barret kernel/sched/core.c | 3 ++- kernel/sched/sched.h | 6 +++++- 2 files changed, 7 insertions(+), 2 deletions(-) diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 98191218d891..c5a1a225d0b4 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -3986,7 +3986,8 @@ static void do_balance_callbacks(struct rq *rq, struct callback_head *head) while (head) { func = (void (*)(struct rq *))head->func; - next = head->next; + /* The last element pointed to itself */ + next = head->next == head ? NULL : head->next; head->next = NULL; head = next; diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h index 10a1522b1e30..66e1a9e5a1af 100644 --- a/kernel/sched/sched.h +++ b/kernel/sched/sched.h @@ -1418,11 +1418,15 @@ queue_balance_callback(struct rq *rq, { lockdep_assert_held(&rq->lock); + /* + * The last element on the list points to itself, so we can always + * detect if head is already enqueued. + */ if (unlikely(head->next || rq->balance_callback == &balance_push_callback)) return; head->func = (void (*)(struct callback_head *))func; - head->next = rq->balance_callback; + head->next = rq->balance_callback ?: head; rq->balance_callback = head; } -- 2.31.0.rc2.261.g7f71774620-goog