From patchwork Wed Nov 24 16:12:19 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Sebastian Andrzej Siewior X-Patchwork-Id: 517420 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 23650C433F5 for ; Wed, 24 Nov 2021 16:12:35 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1345777AbhKXQPn (ORCPT ); Wed, 24 Nov 2021 11:15:43 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:44280 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S241891AbhKXQPm (ORCPT ); Wed, 24 Nov 2021 11:15:42 -0500 Received: from galois.linutronix.de (Galois.linutronix.de [IPv6:2a0a:51c0:0:12e:550::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id BCC97C06173E; Wed, 24 Nov 2021 08:12:32 -0800 (PST) From: Sebastian Andrzej Siewior DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1637770350; 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=uKN/L/evIH8pd44wrAVkgZq5sxjgxZoyOnlYnKYCCYA=; b=XZ7EF4CRFiIZI2UeAAq6e6x9phusLKk0W96gOl54egnHzSTtJo/eYHwrnCVyiFKIzKS92l gZ3L4FOB1VlqJiclj+p0QRPMgbignWTxzRq9MYXyU8YF+TMAjIQGMU74SxZkshdxNqTuto bbX0c0UFJGAyz84WORE/ClVtli7IoGQjlpulVat9Z27gDeLeT+j/dlAIIOgScyAezy3uLl XpMGD28tsC6qQy8Wsl5IGDpiQRMclFtksm7zMz1D3jp3e4EyI+fpDMuLEhUwkE2veX/SUn MdKYMu772U/IdxBgIPeaOkB+6DWd5+YszdCfEW3UXIy7ssg5lfrcjhTq/HmvWg== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1637770350; 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=uKN/L/evIH8pd44wrAVkgZq5sxjgxZoyOnlYnKYCCYA=; b=A7QUA7jAaDw25sXaRqIOJCr6IScUGaPwQT/lHRZY3Jjmh6A7DddmV/WPtGo8dIeEMH/ce7 wQqLwjKVEvfyfgBw== To: Steven Rostedt Cc: linux-kernel@vger.kernel.org, linux-rt-users , Thomas Gleixner , Carsten Emde , John Kacur , Daniel Wagner , Tom Zanussi , "Srivatsa S . Bhat" , Clark Williams , Maarten Lankhorst , bigeasy@linutronix.de Subject: [PATCH RT 1/3] irq_work: Allow irq_work_sync() to sleep if irq_work() no IRQ support. Date: Wed, 24 Nov 2021 17:12:19 +0100 Message-Id: <20211124161221.2224005-2-bigeasy@linutronix.de> In-Reply-To: <20211124161221.2224005-1-bigeasy@linutronix.de> References: <20211123103755.12d4b776@gandalf.local.home> <20211124161221.2224005-1-bigeasy@linutronix.de> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-rt-users@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 Signed-off-by: Peter Zijlstra (Intel) Link: https://lkml.kernel.org/r/20211006111852.1514359-3-bigeasy@linutronix.de --- include/linux/irq_work.h | 10 +++++++++- kernel/irq_work.c | 10 ++++++++++ 2 files changed, 19 insertions(+), 1 deletion(-) diff --git a/include/linux/irq_work.h b/include/linux/irq_work.h index f941f2d7d71ce..3c6d3a96bca0f 100644 --- a/include/linux/irq_work.h +++ b/include/linux/irq_work.h @@ -3,6 +3,7 @@ #define _LINUX_IRQ_WORK_H #include +#include /* * An entry can be in one of four states: @@ -22,6 +23,7 @@ struct irq_work { }; }; void (*func)(struct irq_work *); + struct rcuwait irqwait; }; static inline @@ -29,13 +31,19 @@ void init_irq_work(struct irq_work *work, void (*func)(struct irq_work *)) { atomic_set(&work->flags, 0); work->func = func; + rcuwait_init(&work->irqwait); } #define DEFINE_IRQ_WORK(name, _f) struct irq_work name = { \ .flags = ATOMIC_INIT(0), \ - .func = (_f) \ + .func = (_f), \ + .irqwait = __RCUWAIT_INITIALIZER(irqwait), \ } +static inline bool irq_work_is_busy(struct irq_work *work) +{ + return atomic_read(&work->flags) & IRQ_WORK_BUSY; +} bool irq_work_queue(struct irq_work *work); bool irq_work_queue_on(struct irq_work *work, int cpu); diff --git a/kernel/irq_work.c b/kernel/irq_work.c index 8183d30e1bb1c..8969aff790e21 100644 --- a/kernel/irq_work.c +++ b/kernel/irq_work.c @@ -165,6 +165,9 @@ void irq_work_single(void *arg) */ flags &= ~IRQ_WORK_PENDING; (void)atomic_cmpxchg(&work->flags, flags, flags & ~IRQ_WORK_BUSY); + + if (!arch_irq_work_has_interrupt()) + rcuwait_wake_up(&work->irqwait); } static void irq_work_run_list(struct llist_head *list) @@ -231,6 +234,13 @@ void irq_work_tick_soft(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; + } while (atomic_read(&work->flags) & IRQ_WORK_BUSY) cpu_relax();