From patchwork Fri Apr 16 10:10:41 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Dillon Min X-Patchwork-Id: 423659 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-15.7 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI, SPF_HELO_NONE, SPF_PASS, URIBL_BLOCKED, USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 326A7C433ED for ; Fri, 16 Apr 2021 10:10:55 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 12594610FB for ; Fri, 16 Apr 2021 10:10:55 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S239096AbhDPKLS (ORCPT ); Fri, 16 Apr 2021 06:11:18 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:42258 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235372AbhDPKLR (ORCPT ); Fri, 16 Apr 2021 06:11:17 -0400 Received: from mail-pj1-x102d.google.com (mail-pj1-x102d.google.com [IPv6:2607:f8b0:4864:20::102d]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id E1D74C061574; Fri, 16 Apr 2021 03:10:51 -0700 (PDT) Received: by mail-pj1-x102d.google.com with SMTP id e8-20020a17090a7288b029014e51f5a6baso9076185pjg.2; Fri, 16 Apr 2021 03:10:51 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=from:to:cc:subject:date:message-id; bh=A/7hIeNkh74sMxQ2VoT+6Wb/XxhlYBDSbBqmEWtFsMs=; b=c79qb3AjMlo1Z8G/mAYAiOnq/4a7c+i4Jom/W81ehb6DnIfKOzIBQiUIq9mKKAMARo PBgsd5rq5IVVGzuy+V+5HUabNdELc1rtuVP90E+ITMmpLsPr068Gm2BwTtIawqmQmTjU 3kGxB3pPrbDah9+K2vEpCT2zbIa6t37VjzbTyDflz0xamHlE3yIH4p56JjyKWMt6+ZHQ Sj038Cnp4xo42nLHZmmlscTOzj7i4VXMk/FMmGDRy5R6rcrkSzwN6EEJDya0bQTq0GjG jhKRIa2iimZW61QRHZ5y/TVUt3OugdR/nI/2MkOGBVk3AxNaedM3opJpguEh1Hbmwudg beog== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id; bh=A/7hIeNkh74sMxQ2VoT+6Wb/XxhlYBDSbBqmEWtFsMs=; b=rx/lR0uMcxWtIvHgqNq9NZaBjL++KAByHTzkmeMB0KDXohw0fIh/JD0AdIS7uxdwqY 2Ccv1v/W317qxOa1SSiYwiHeABooeXHnxVZm1QbmaFVA3whNao/F/GB6tqXKC3hc4CWg XO2zn+/s/skkQPOZQDgU5jRAassD/eSNPJhVrq94hI7e04SRreQ3MpHBLyynJ0aM4SnL XJOPYOq8DNuWb1qm8MbUMdrjvMhpWI3GYycNazjhzC7ckGlDozxtIiThO60qqpZBNHvK As3kN++jiI8bWcO0/iqE3EMgZejS3zcte3YgA7VMEkV9sy+bh2+WqgseNaHHp/nIUJHu b5+A== X-Gm-Message-State: AOAM531L3L67A9Nw6Bt90IMhHPSnr1zREMXdPu75Zx6kVX/3Y301+t9K wbTSJgjVq4hdgAOyERs+22Y= X-Google-Smtp-Source: ABdhPJyL6O0IvkWzDC0x4hnKmxrsWJIdNewo78CdAaYdxeGULaN/XIlJR3v96Xo95TfHQscGqhU7Qw== X-Received: by 2002:a17:90b:4a46:: with SMTP id lb6mr9025629pjb.45.1618567851417; Fri, 16 Apr 2021 03:10:51 -0700 (PDT) Received: from fmin-OptiPlex-7060.nreal.work ([137.59.103.165]) by smtp.gmail.com with ESMTPSA id t67sm4601440pfb.210.2021.04.16.03.10.43 (version=TLS1_2 cipher=ECDHE-ECDSA-AES128-GCM-SHA256 bits=128/128); Fri, 16 Apr 2021 03:10:46 -0700 (PDT) From: dillon.minfei@gmail.com To: gregkh@linuxfoundation.org, jirislaby@kernel.org, mcoquelin.stm32@gmail.com, alexandre.torgue@foss.st.com, lkp@intel.com, johan@kernel.org, gerald.baeza@foss.st.com, erwan.leray@foss.st.com Cc: linux-serial@vger.kernel.org, linux-stm32@st-md-mailman.stormreply.com, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, kbuild-all@lists.01.org, clang-built-linux@googlegroups.com, dillon min Subject: [PATCH v3] serial: stm32: optimize spin lock usage Date: Fri, 16 Apr 2021 18:10:41 +0800 Message-Id: <1618567841-18546-1-git-send-email-dillon.minfei@gmail.com> X-Mailer: git-send-email 2.7.4 Precedence: bulk List-ID: X-Mailing-List: linux-serial@vger.kernel.org From: dillon min This patch aims to fix two potential bug: - no lock to protect uart register in this case stm32_usart_threaded_interrupt() spin_lock(&port->lock); ... stm32_usart_receive_chars() uart_handle_sysrq_char(); sysrq_function(); printk(); stm32_usart_console_write(); locked = 0; //since port->sysrq is not zero, no lock to protect forward register access. - if add spin_trylock_irqsave() to protect uart register for sysrq = 1 case, that might got recursive locking under UP. So, use uart_prepare_sysrq_char(), uart_unlock_and_check_sysrq() move sysrq handler position to irq/thread_d handler, just record sysrq_ch in stm32_usart_receive_chars() by uart_prepare_sysrq_char() delay the sysrq process to next interrupt handler. new flow: stm32_usart_threaded_interrupt()/stm32_usart_interrupt() spin_lock_irqsave(&port->lock); ... uart_unlock_and_check_sysrq(); spin_unlock_irqrestore(); handle_sysrq(sysrq_ch); stm32_usart_threaded_interrupt()//stm32_usart_interrupt() return Cc: Johan Hovold Cc: Alexandre Torgue Cc: Maxime Coquelin Cc: Gerald Baeza Cc: Erwan Le Ray Reported-by: kernel test robot Signed-off-by: dillon min --- v3: add uart_prepare_sysrq_char(), uart_unlock_and_check_sysrq() to move sysrq handler inside interrupt routinei to avoid recursive locking, according to Johan Hovold suggestion, thanks. drivers/tty/serial/stm32-usart.c | 24 +++++++++++------------- 1 file changed, 11 insertions(+), 13 deletions(-) diff --git a/drivers/tty/serial/stm32-usart.c b/drivers/tty/serial/stm32-usart.c index b3675cf25a69..981f50ec784e 100644 --- a/drivers/tty/serial/stm32-usart.c +++ b/drivers/tty/serial/stm32-usart.c @@ -271,7 +271,7 @@ static void stm32_usart_receive_chars(struct uart_port *port, bool threaded) } } - if (uart_handle_sysrq_char(port, c)) + if (uart_prepare_sysrq_char(port, c)) continue; uart_insert_char(port, sr, USART_SR_ORE, c, flag); } @@ -457,9 +457,10 @@ static irqreturn_t stm32_usart_interrupt(int irq, void *ptr) struct uart_port *port = ptr; struct stm32_port *stm32_port = to_stm32_port(port); const struct stm32_usart_offsets *ofs = &stm32_port->info->ofs; + unsigned long flags; u32 sr; - spin_lock(&port->lock); + spin_lock_irqsave(&port->lock, flags); sr = readl_relaxed(port->membase + ofs->isr); @@ -477,7 +478,7 @@ static irqreturn_t stm32_usart_interrupt(int irq, void *ptr) if ((sr & USART_SR_TXE) && !(stm32_port->tx_ch)) stm32_usart_transmit_chars(port); - spin_unlock(&port->lock); + uart_unlock_and_check_sysrq(port, flags); if (stm32_port->rx_ch) return IRQ_WAKE_THREAD; @@ -489,13 +490,14 @@ static irqreturn_t stm32_usart_threaded_interrupt(int irq, void *ptr) { struct uart_port *port = ptr; struct stm32_port *stm32_port = to_stm32_port(port); + unsigned long flags; - spin_lock(&port->lock); + spin_lock_irqsave(&port->lock, flags); if (stm32_port->rx_ch) stm32_usart_receive_chars(port, true); - spin_unlock(&port->lock); + uart_unlock_and_check_sysrq(port, flags); return IRQ_HANDLED; } @@ -1354,13 +1356,10 @@ static void stm32_usart_console_write(struct console *co, const char *s, u32 old_cr1, new_cr1; int locked = 1; - local_irq_save(flags); - if (port->sysrq) - locked = 0; - else if (oops_in_progress) - locked = spin_trylock(&port->lock); + if (oops_in_progress) + locked = spin_trylock_irqsave(&port->lock, flags); else - spin_lock(&port->lock); + spin_lock_irqsave(&port->lock, flags); /* Save and disable interrupts, enable the transmitter */ old_cr1 = readl_relaxed(port->membase + ofs->cr1); @@ -1374,8 +1373,7 @@ static void stm32_usart_console_write(struct console *co, const char *s, writel_relaxed(old_cr1, port->membase + ofs->cr1); if (locked) - spin_unlock(&port->lock); - local_irq_restore(flags); + spin_unlock_irqrestore(&port->lock, flags); } static int stm32_usart_console_setup(struct console *co, char *options)