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 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id A2FE6C433F5 for ; Wed, 6 Oct 2021 11:19:11 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 90C6161130 for ; Wed, 6 Oct 2021 11:19:11 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S238267AbhJFLVB (ORCPT ); Wed, 6 Oct 2021 07:21:01 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:49454 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S238280AbhJFLUw (ORCPT ); Wed, 6 Oct 2021 07:20:52 -0400 Received: from galois.linutronix.de (Galois.linutronix.de [IPv6:2a0a:51c0:0:12e:550::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 0FC8AC061760 for ; Wed, 6 Oct 2021 04:19:00 -0700 (PDT) From: Sebastian Andrzej Siewior DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1633519137; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=DWlP05vTdXrgx690tmJEWR6jiTgZ7aKq/O1XxxTStbo=; b=s8dAjqcm4gidLrd47qWCTXXbx7wY5HMCpo1GBLU6Gq9HDViUoSfsQCPnouHtxBir3oXI0M lC0KTHbRP8ZVvzblG6B7RRmwCaj8MQ54CKNIpcTM7l12FrHesDQux0KodtjnNVvuHBdVlc tMaci4hV0UDhphZPtTj+tkVUFGMAjjkvxnHCh2g6e1AFPVme9IAJD/JDhVENjtAxO3jMWe oht4JeNFR8BbgtXuQbfgNR8q0GE8VwY+2HNQN5dBFF24WuLyYDnvibfdNTTBUTzDCpyP/h RXsqMZFStoxpt52Qpdd/4BKwcgRVm3REKH5dY2IIJq8n6+ZdRJN81CTtS7na/g== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1633519137; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=DWlP05vTdXrgx690tmJEWR6jiTgZ7aKq/O1XxxTStbo=; b=DNVqPT9bOLyl/9w+CzUnYBLAb6sY2EJQIi9ZRwu7Vu8E7Haj3zMoqCKfJ2BvKrEFsLiH+l wb5IS7HZ1OBXJvCA== To: linux-kernel@vger.kernel.org Cc: Peter Zijlstra , Thomas Gleixner , Sebastian Andrzej Siewior Subject: [PATCH v2 2/4] irq_work: Allow irq_work_sync() to sleep if irq_work() no IRQ support. Date: Wed, 6 Oct 2021 13:18:50 +0200 Message-Id: <20211006111852.1514359-3-bigeasy@linutronix.de> In-Reply-To: <20211006111852.1514359-1-bigeasy@linutronix.de> References: <20211006111852.1514359-1-bigeasy@linutronix.de> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org irq_work() triggers instantly an interrupt if supported by the architecture. Otherwise the work will be processed on the next timer tick. In worst case irq_work_sync() could spin up to a jiffy. irq_work_sync() is usually used in tear down context which is fully preemptible. Based on review irq_work_sync() is invoked from preemptible context and there is one waiter at a time. This qualifies it to use rcuwait for synchronisation. Let irq_work_sync() synchronize with rcuwait if the architecture processes irqwork via the timer tick. Signed-off-by: Sebastian Andrzej Siewior --- include/linux/irq_work.h | 3 +++ kernel/irq_work.c | 10 ++++++++++ 2 files changed, 13 insertions(+) diff --git a/include/linux/irq_work.h b/include/linux/irq_work.h index ec2a47a81e423..b48955e9c920e 100644 --- a/include/linux/irq_work.h +++ b/include/linux/irq_work.h @@ -3,6 +3,7 @@ #define _LINUX_IRQ_WORK_H =20 #include +#include =20 /* * An entry can be in one of four states: @@ -16,11 +17,13 @@ struct irq_work { struct __call_single_node node; void (*func)(struct irq_work *); + struct rcuwait irqwait; }; =20 #define __IRQ_WORK_INIT(_func, _flags) (struct irq_work){ \ .node =3D { .u_flags =3D (_flags), }, \ .func =3D (_func), \ + .irqwait =3D __RCUWAIT_INITIALIZER(irqwait), \ } =20 #define IRQ_WORK_INIT(_func) __IRQ_WORK_INIT(_func, 0) diff --git a/kernel/irq_work.c b/kernel/irq_work.c index db8c248ebc8c8..e789beda8297d 100644 --- a/kernel/irq_work.c +++ b/kernel/irq_work.c @@ -160,6 +160,9 @@ void irq_work_single(void *arg) * else claimed it meanwhile. */ (void)atomic_cmpxchg(&work->node.a_flags, flags, flags & ~IRQ_WORK_BUSY); + + if (!arch_irq_work_has_interrupt()) + rcuwait_wake_up(&work->irqwait); } =20 static void irq_work_run_list(struct llist_head *list) @@ -204,6 +207,13 @@ void irq_work_tick(void) void irq_work_sync(struct irq_work *work) { lockdep_assert_irqs_enabled(); + might_sleep(); + + if (!arch_irq_work_has_interrupt()) { + rcuwait_wait_event(&work->irqwait, !irq_work_is_busy(work), + TASK_UNINTERRUPTIBLE); + return; + } =20 while (irq_work_is_busy(work)) cpu_relax(); --=20 2.33.0