From nobody Thu May 7 20:06:12 2026 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 80099C433EF for ; Thu, 19 May 2022 11:02:57 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S237140AbiESLC4 (ORCPT ); Thu, 19 May 2022 07:02:56 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:51358 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S237177AbiESLCv (ORCPT ); Thu, 19 May 2022 07:02:51 -0400 Received: from bhuna.collabora.co.uk (bhuna.collabora.co.uk [46.235.227.227]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 1883D5DA5D for ; Thu, 19 May 2022 04:02:46 -0700 (PDT) Received: from [127.0.0.1] (localhost [127.0.0.1]) (Authenticated sender: dmitry.osipenko) with ESMTPSA id A1BE41F45A4D DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=collabora.com; s=mail; t=1652958165; bh=Z+gW0P5sGsUp4ykJPGmElehexTGF1kbDnbejPEKwZ9c=; h=From:To:Cc:Subject:Date:From; b=Uevjx3rYjqqSNuK62J8Fbi8xsTvoSJcJPJl2ZQlG7jjH4/zUyWJfKs6jXO21mZkm7 ffZiL8xfeFqsx7HmK5ldFXe6YdvanDGgOMevV6vzTgP+xR6B9NBfxQL42v6ig/x2wg VDvGRFlfWCwLh45yn8AwTZKtKUSSGcRBIHRqMJh2Nf/vOILLuIAxk1VtJp6RcQMx+9 0B3JAwxsBgVWxX0WaLWzmIGfoa+qiu3C09f6XzrgTsRLyzW6OJfuWHlxuLiE8Ia5ob EFCHEbIBqBsF0usM9p4P3C0X7s/UStj51gkA6nVIfLyWqKt2Vnik/wUnyeyIm5tZx3 OhIViF2Smtj6A== From: Dmitry Osipenko To: "Rafael J . Wysocki" , =?UTF-8?q?Micha=C5=82=20Miros=C5=82aw?= Cc: linux-kernel@vger.kernel.org Subject: [PATCH v10] notifier: Add atomic_notifier_call_chain_is_empty() Date: Thu, 19 May 2022 14:02:32 +0300 Message-Id: <20220519110232.1198823-1-dmitry.osipenko@collabora.com> X-Mailer: git-send-email 2.35.3 MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Add atomic_notifier_call_chain_is_empty() that returns true if given atomic call chain is empty. The first user of this new notifier API function will be the kernel power-off core code that will support power-off call chains. The core code will need to check whether there is a power-off handler registered at all in order to decide whether to halt machine or power it off. Reviewed-by: Micha=C5=82 Miros=C5=82aw Signed-off-by: Dmitry Osipenko --- Changelog: v10: - Corrected another doc-comment typo s/atomicnotifier/atomic_notifier/. v9: - Extended commit message with a usage example. - Corrected doc-comment with s/blocking/atomic/. include/linux/notifier.h | 2 ++ kernel/notifier.c | 13 +++++++++++++ 2 files changed, 15 insertions(+) diff --git a/include/linux/notifier.h b/include/linux/notifier.h index 87069b8459af..95e2440037de 100644 --- a/include/linux/notifier.h +++ b/include/linux/notifier.h @@ -173,6 +173,8 @@ extern int blocking_notifier_call_chain_robust(struct b= locking_notifier_head *nh extern int raw_notifier_call_chain_robust(struct raw_notifier_head *nh, unsigned long val_up, unsigned long val_down, void *v); =20 +extern bool atomic_notifier_call_chain_is_empty(struct atomic_notifier_hea= d *nh); + #define NOTIFY_DONE 0x0000 /* Don't care */ #define NOTIFY_OK 0x0001 /* Suits me */ #define NOTIFY_STOP_MASK 0x8000 /* Don't call further */ diff --git a/kernel/notifier.c b/kernel/notifier.c index ba005ebf4730..137b902c985b 100644 --- a/kernel/notifier.c +++ b/kernel/notifier.c @@ -204,6 +204,19 @@ int atomic_notifier_call_chain(struct atomic_notifier_= head *nh, EXPORT_SYMBOL_GPL(atomic_notifier_call_chain); NOKPROBE_SYMBOL(atomic_notifier_call_chain); =20 +/** + * atomic_notifier_call_chain_is_empty - Check whether notifier chain is e= mpty + * @nh: Pointer to head of the atomic notifier chain + * + * Checks whether notifier chain is empty. + * + * Returns true is notifier chain is empty, false otherwise. + */ +bool atomic_notifier_call_chain_is_empty(struct atomic_notifier_head *nh) +{ + return !rcu_access_pointer(nh->head); +} + /* * Blocking notifier chain routines. All access to the chain is * synchronized by an rwsem. --=20 2.35.3