From patchwork Fri Apr 29 11:52:48 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Thomas Pfaff X-Patchwork-Id: 567665 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 E53BDC43217 for ; Fri, 29 Apr 2022 11:53:14 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1358696AbiD2L43 (ORCPT ); Fri, 29 Apr 2022 07:56:29 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:54054 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S239331AbiD2L42 (ORCPT ); Fri, 29 Apr 2022 07:56:28 -0400 Received: from mail.pcs.gmbh (mail.pcs.gmbh [89.27.162.52]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 09390C6ECD; Fri, 29 Apr 2022 04:53:08 -0700 (PDT) Received: from mail.csna.de (mail.csna.de [89.27.162.50]) by mail.pcs.gmbh with ESMTPA ; Fri, 29 Apr 2022 13:52:48 +0200 Received: from EXCHANGE2019.pcs.ditec.de (mail.pcs.com [89.27.162.5]) by mail.csna.de with ESMTPA ; Fri, 29 Apr 2022 13:52:48 +0200 Received: from EXCHANGE2019.pcs.ditec.de (192.168.8.214) by EXCHANGE2019.pcs.ditec.de (192.168.8.214) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.986.22; Fri, 29 Apr 2022 13:52:48 +0200 Received: from lxtpfaff.pcs.ditec.de (192.168.9.96) by EXCHANGE2019.pcs.ditec.de (192.168.8.214) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.986.22 via Frontend Transport; Fri, 29 Apr 2022 13:52:48 +0200 Date: Fri, 29 Apr 2022 13:52:48 +0200 From: Thomas Pfaff To: Thomas Gleixner CC: , , Hillf Danton , Marc Zyngier Subject: [PATCH v2] irq/core: synchronize irq_thread startup Message-ID: <1e3f96b7-9294-1534-e83b-efe3602f876f@pcs.com> MIME-Version: 1.0 X-KSE-ServerInfo: EXCHANGE2019.pcs.ditec.de, 9 X-KSE-AntiSpam-Interceptor-Info: white sender email list X-KSE-AttachmentFiltering-Interceptor-Info: protection disabled X-KSE-Antivirus-Interceptor-Info: scan successful X-KSE-Antivirus-Info: Clean, bases: 29.04.2022 09:07:00 X-KSE-BulkMessagesFiltering-Scan-Result: protection disabled Precedence: bulk List-ID: X-Mailing-List: linux-rt-users@vger.kernel.org From: Thomas Pfaff While running "while /bin/true; do setserial /dev/ttyS0 uart none; setserial /dev/ttyS0 uart 16550A; done" on a kernel with threaded irqs, setserial is hung after some calls. setserial opens the device, this will install an irq handler if the uart is not none, followed by TIOCGSERIAL and TIOCSSERIAL ioctls. Then the device is closed. On close, synchronize_irq() is called by serial_core. If the close comes too fast, the irq_thread does not really start, it is terminated immediately without going into irq_thread(). But an interrupt might already been handled by irq_default_primary_handler(), going to __irq_wake_thread() and incrementing threads_active. If this happens, synchronize_irq() will hang forever, because the irq_thread is already dead, and threads_active will never be decremented. The fix is to make sure that the irq_thread is really started during __setup_irq(). Signed-off-by: Thomas Pfaff --- v1-v2: - use already existing resources diff --git a/kernel/irq/internals.h b/kernel/irq/internals.h index 99cbdf55a8bd..dca57bed0d96 100644 --- a/kernel/irq/internals.h +++ b/kernel/irq/internals.h @@ -29,12 +29,14 @@ extern struct irqaction chained_action; * IRQTF_WARNED - warning "IRQ_WAKE_THREAD w/o thread_fn" has been printed * IRQTF_AFFINITY - irq thread is requested to adjust affinity * IRQTF_FORCED_THREAD - irq action is force threaded + * IRQTF_UP - signals that irq thread is ready */ enum { IRQTF_RUNTHREAD, IRQTF_WARNED, IRQTF_AFFINITY, IRQTF_FORCED_THREAD, + IRQTF_UP, }; /* diff --git a/kernel/irq/manage.c b/kernel/irq/manage.c index f1d5a94c6c9f..7efa24629694 100644 --- a/kernel/irq/manage.c +++ b/kernel/irq/manage.c @@ -1263,6 +1263,30 @@ static void irq_wake_secondary(struct irq_desc *desc, struct irqaction *action) raw_spin_unlock_irq(&desc->lock); } +/* + * Internal function to notify that irq_thread is ready + */ +static void irq_thread_is_up(struct irq_desc *desc, + struct irqaction *action) +{ + set_bit(IRQTF_UP, &action->thread_flags); + wake_up(&desc->wait_for_threads); +} + +/* + * Internal function to wake up irq_thread + * and wait until it is really up + */ +static void wait_for_irq_thread_startup(struct irq_desc *desc, + struct irqaction *action) +{ + if (action && action->thread) { + wake_up_process(action->thread); + wait_event(desc->wait_for_threads, + test_bit(IRQTF_UP, &action->thread_flags)); + } +} + /* * Interrupt handler thread */ @@ -1287,6 +1311,8 @@ static int irq_thread(void *data) irq_thread_check_affinity(desc, action); + irq_thread_is_up (desc, action); + while (!irq_wait_for_interrupt(action)) { irqreturn_t action_ret; @@ -1522,6 +1548,8 @@ __setup_irq(unsigned int irq, struct irq_desc *desc, struct irqaction *new) } } + init_waitqueue_head(&desc->wait_for_threads); + /* * Create a handler thread when a thread function is supplied * and the interrupt does not nest into another interrupt @@ -1698,8 +1726,6 @@ __setup_irq(unsigned int irq, struct irq_desc *desc, struct irqaction *new) } if (!shared) { - init_waitqueue_head(&desc->wait_for_threads); - /* Setup the type (level, edge polarity) if configured: */ if (new->flags & IRQF_TRIGGER_MASK) { ret = __irq_set_trigger(desc, @@ -1795,14 +1821,8 @@ __setup_irq(unsigned int irq, struct irq_desc *desc, struct irqaction *new) irq_setup_timings(desc, new); - /* - * Strictly no need to wake it up, but hung_task complains - * when no hard interrupt wakes the thread up. - */ - if (new->thread) - wake_up_process(new->thread); - if (new->secondary) - wake_up_process(new->secondary->thread); + wait_for_irq_thread_startup(desc, new); + wait_for_irq_thread_startup(desc, new->secondary); register_irq_proc(irq, desc); new->dir = NULL;