From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pl0-f65.google.com ([209.85.160.65]:45806 "EHLO mail-pl0-f65.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726992AbeGRXjW (ORCPT ); Wed, 18 Jul 2018 19:39:22 -0400 Received: by mail-pl0-f65.google.com with SMTP id 94-v6so2683397ple.12 for ; Wed, 18 Jul 2018 15:59:16 -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> In-Reply-To: References: Sender: linux-fsdevel-owner@vger.kernel.org List-ID: 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