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=-2.8 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS,T_DKIMWL_WL_MED, URIBL_BLOCKED,USER_AGENT_GIT 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 BC486ECDFB8 for ; Wed, 18 Jul 2018 22:59:19 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 6A1C92075E for ; Wed, 18 Jul 2018 22:59:19 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=osandov-com.20150623.gappssmtp.com header.i=@osandov-com.20150623.gappssmtp.com header.b="gKKSfyFh" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 6A1C92075E Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=osandov.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730316AbeGRXjX (ORCPT ); Wed, 18 Jul 2018 19:39:23 -0400 Received: from mail-pl0-f68.google.com ([209.85.160.68]:40207 "EHLO mail-pl0-f68.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729974AbeGRXjW (ORCPT ); Wed, 18 Jul 2018 19:39:22 -0400 Received: by mail-pl0-f68.google.com with SMTP id s17-v6so2684726plp.7 for ; Wed, 18 Jul 2018 15:59:16 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=osandov-com.20150623.gappssmtp.com; s=20150623; h=from:to:cc:subject:date:message-id:in-reply-to:references; bh=lnhh2st4VX6fehK5+kTz/Y62FrZVJOTwdJg1BYsX/0s=; b=gKKSfyFh/FCLHtCMA0kiqlE5CiijuIkzB+rU0uXmOJkm8MWdAonRtkDeAeTojl5eKV G5jChoGSvQhFrIFPthuvPZLAt944+xJ9e/0NOa6KLae4Bkb/Nu8R9xfXXJUlLadxMQUD kRXwJIF2vkxhoRn7Kv09R4V5N4bdAgZYKqKPW2Zw6Y1f4+C7krfhzg3OG9+IS/AAjA+j DLPCEJerGHgLBYC6UX0Kj8tj8F+uptRsub6+S5cLJQ73Nk7e+N2nFQdHadEABdSV/sJX m531CksYuv6BXdup7P81hbz6eGU+pgiksyJz74Q0qiFMRQ8OLkeA2pNCsF2fiJoXEx97 Ej5Q== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references; bh=lnhh2st4VX6fehK5+kTz/Y62FrZVJOTwdJg1BYsX/0s=; b=TkF8GlORz46/4pdE7E/vVt9OrN1hicAThOqTjUceu5UBvpt3SnCdXnQ8JNFhe+mDor bDCyXWqLo0vDnDOnDcrX63R9IQrREedJ1VzkdBpBBC88LHDgdFiePMCUwlm5v3ZJbPp9 WEmn5uL/TNuv2JfUgO/5Gly0UVIZlnWhAjWPJjWJ+UtVTcWbKk3Yh2XRQUQd2sawWQOB o8CbYMNz2FywVrro19QVJjWm9BcvIR2eVACyyNAVQObuL6UaDp+rfOjlAqeQ33XgjnAy i7wGduQdumEV5ib6XLJhebSeS+IL7b2X2b+4cPJ/nVb3QyNTcTLKpIadcJtifySaOpDL 2V9w== X-Gm-Message-State: AOUpUlHP1FoM5ULvXA+Naqp1nlXCZObRtVCEGXSNNycmIQvgVm3pjJuV euvP2XWzL+kE3R0/JAi/2RTEkkp2BuY= X-Google-Smtp-Source: AAOMgpc8447Ag1hXtUydGpCL49hHJ4EVktEXb0qgfGD60nGKEio6lV+p/SKdrQrehrzV/AAq27fOVQ== X-Received: by 2002:a17:902:599b:: with SMTP id p27-v6mr7562887pli.191.1531954755568; Wed, 18 Jul 2018 15:59:15 -0700 (PDT) Received: from vader.hsd1.wa.comcast.net ([2601:602:8800:a9a9:e6a7:a0ff:fe0b:c9a8]) by smtp.gmail.com with ESMTPSA id s16-v6sm6377946pfm.114.2018.07.18.15.59.14 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 18 Jul 2018 15:59:15 -0700 (PDT) From: Omar Sandoval To: linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, Andrew Morton Cc: Alexey Dobriyan , Eric Biederman , James Morse , Bhupesh Sharma , kernel-team@fb.com Subject: [PATCH v3 2/8] proc/kcore: don't grab lock for memory hotplug notifier Date: Wed, 18 Jul 2018 15:58:42 -0700 Message-Id: <0a4bc89f4dbde8b5b2ea309f7b4fb6a85fe29df2.1531953780.git.osandov@fb.com> X-Mailer: git-send-email 2.18.0 In-Reply-To: References: Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Omar Sandoval The memory hotplug notifier kcore_callback() only needs kclist_lock to prevent races with __kcore_update_ram(), but we can easily eliminate that race by using an atomic xchg() in __kcore_update_ram(). This is preparation for converting kclist_lock to an rwsem. Signed-off-by: Omar Sandoval --- fs/proc/kcore.c | 6 ++---- 1 file changed, 2 insertions(+), 4 deletions(-) diff --git a/fs/proc/kcore.c b/fs/proc/kcore.c index b0b9a76f28d6..e83f15a4f66d 100644 --- a/fs/proc/kcore.c +++ b/fs/proc/kcore.c @@ -118,7 +118,7 @@ static void __kcore_update_ram(struct list_head *list) LIST_HEAD(garbage); write_lock(&kclist_lock); - if (kcore_need_update) { + if (xchg(&kcore_need_update, 0)) { list_for_each_entry_safe(pos, tmp, &kclist_head, list) { if (pos->type == KCORE_RAM || pos->type == KCORE_VMEMMAP) @@ -127,7 +127,6 @@ static void __kcore_update_ram(struct list_head *list) list_splice_tail(list, &kclist_head); } else list_splice(list, &garbage); - kcore_need_update = 0; proc_root_kcore->size = get_kcore_size(&nphdr, &size); write_unlock(&kclist_lock); @@ -593,9 +592,8 @@ static int __meminit kcore_callback(struct notifier_block *self, switch (action) { case MEM_ONLINE: case MEM_OFFLINE: - write_lock(&kclist_lock); kcore_need_update = 1; - write_unlock(&kclist_lock); + break; } return NOTIFY_OK; } -- 2.18.0