From patchwork Fri Jun 17 10:05:49 2016 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Nicolas Ferre X-Patchwork-Id: 9183211 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork.web.codeaurora.org (Postfix) with ESMTP id 3C87060776 for ; Fri, 17 Jun 2016 10:08:37 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 2CD0728385 for ; Fri, 17 Jun 2016 10:08:37 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 2151628399; Fri, 17 Jun 2016 10:08:37 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-4.2 required=2.0 tests=BAYES_00, RCVD_IN_DNSWL_MED autolearn=unavailable version=3.3.1 Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.9]) (using TLSv1.2 with cipher AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.wl.linuxfoundation.org (Postfix) with ESMTPS id B2F5728385 for ; Fri, 17 Jun 2016 10:08:36 +0000 (UTC) Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.80.1 #2 (Red Hat Linux)) id 1bDqgC-0000qi-PN; Fri, 17 Jun 2016 10:07:12 +0000 Received: from eusmtp01.atmel.com ([212.144.249.243]) by bombadil.infradead.org with esmtps (Exim 4.80.1 #2 (Red Hat Linux)) id 1bDqg8-0000Y0-8D for linux-arm-kernel@lists.infradead.org; Fri, 17 Jun 2016 10:07:10 +0000 Received: from tenerife.corp.atmel.com (10.161.101.13) by eusmtp01.atmel.com (10.161.101.31) with Microsoft SMTP Server id 14.3.235.1; Fri, 17 Jun 2016 12:06:40 +0200 From: Nicolas Ferre To: Greg Kroah-Hartman , , Alexandre Belloni , Subject: [PATCH 4/4] tty/serial: atmel: enforce tasklet init and termination sequences Date: Fri, 17 Jun 2016 12:05:49 +0200 Message-ID: <5a52e1fbd8ec126bebfcd00f35bfe5af605ee914.1466157015.git.nicolas.ferre@atmel.com> X-Mailer: git-send-email 2.9.0 In-Reply-To: References: MIME-Version: 1.0 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20160617_030708_703839_996E7BB0 X-CRM114-Status: GOOD ( 13.27 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.20 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Boris BREZILLON , Ludovic Desroches , Nicolas Ferre , linux-kernel@vger.kernel.org Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+patchwork-linux-arm=patchwork.kernel.org@lists.infradead.org X-Virus-Scanned: ClamAV using ClamSMTP As some race conditions are identified in the termination process of tasklets, enforce the atmel_shutdown() sequence. This way we make sure that no new tasklets or software timer are scheduled during shutdown process. An atomic flag is positioned to give this information throughout the code. We also remove tasklet_disable() calls that were leading to deadlocks while stopping the driver. A simpler init/kill sequence is used. Signed-off-by: Nicolas Ferre --- drivers/tty/serial/atmel_serial.c | 61 ++++++++++++++++++++++++--------------- 1 file changed, 38 insertions(+), 23 deletions(-) diff --git a/drivers/tty/serial/atmel_serial.c b/drivers/tty/serial/atmel_serial.c index 857016367a7a..00c4365e6239 100644 --- a/drivers/tty/serial/atmel_serial.c +++ b/drivers/tty/serial/atmel_serial.c @@ -153,6 +153,7 @@ struct atmel_uart_port { struct scatterlist sg_rx; struct tasklet_struct tasklet_rx; struct tasklet_struct tasklet_tx; + atomic_t tasklet_shutdown; unsigned int irq_status_prev; unsigned int tx_len; @@ -286,6 +287,13 @@ static bool atmel_use_fifo(struct uart_port *port) return atmel_port->fifo_size; } +static void atmel_tasklet_schedule(struct atmel_uart_port *atmel_port, + struct tasklet_struct *t) +{ + if (!atomic_read(&atmel_port->tasklet_shutdown)) + tasklet_schedule(t); +} + static unsigned int atmel_get_lines_status(struct uart_port *port) { struct atmel_uart_port *atmel_port = to_atmel_uart_port(port); @@ -715,7 +723,7 @@ static void atmel_rx_chars(struct uart_port *port) status = atmel_uart_readl(port, ATMEL_US_CSR); } - tasklet_schedule(&atmel_port->tasklet_rx); + atmel_tasklet_schedule(atmel_port, &atmel_port->tasklet_rx); } /* @@ -786,7 +794,7 @@ static void atmel_complete_tx_dma(void *arg) * remaining data from the beginning of xmit->buf to xmit->head. */ if (!uart_circ_empty(xmit)) - tasklet_schedule(&atmel_port->tasklet_tx); + atmel_tasklet_schedule(atmel_port, &atmel_port->tasklet_tx); spin_unlock_irqrestore(&port->lock, flags); } @@ -971,7 +979,7 @@ static void atmel_complete_rx_dma(void *arg) struct uart_port *port = arg; struct atmel_uart_port *atmel_port = to_atmel_uart_port(port); - tasklet_schedule(&atmel_port->tasklet_rx); + atmel_tasklet_schedule(atmel_port, &atmel_port->tasklet_rx); } static void atmel_release_rx_dma(struct uart_port *port) @@ -1011,7 +1019,7 @@ static void atmel_rx_from_dma(struct uart_port *port) if (dmastat == DMA_ERROR) { dev_dbg(port->dev, "Get residue error, restart tasklet\n"); atmel_uart_writel(port, ATMEL_US_IER, ATMEL_US_TIMEOUT); - tasklet_schedule(&atmel_port->tasklet_rx); + atmel_tasklet_schedule(atmel_port, &atmel_port->tasklet_rx); return; } @@ -1165,8 +1173,11 @@ static void atmel_uart_timer_callback(unsigned long data) struct uart_port *port = (void *)data; struct atmel_uart_port *atmel_port = to_atmel_uart_port(port); - tasklet_schedule(&atmel_port->tasklet_rx); - mod_timer(&atmel_port->uart_timer, jiffies + uart_poll_timeout(port)); + if (!atomic_read(&atmel_port->tasklet_shutdown)) { + tasklet_schedule(&atmel_port->tasklet_rx); + mod_timer(&atmel_port->uart_timer, + jiffies + uart_poll_timeout(port)); + } } /* @@ -1188,7 +1199,8 @@ atmel_handle_receive(struct uart_port *port, unsigned int pending) if (pending & (ATMEL_US_ENDRX | ATMEL_US_TIMEOUT)) { atmel_uart_writel(port, ATMEL_US_IDR, (ATMEL_US_ENDRX | ATMEL_US_TIMEOUT)); - tasklet_schedule(&atmel_port->tasklet_rx); + atmel_tasklet_schedule(atmel_port, + &atmel_port->tasklet_rx); } if (pending & (ATMEL_US_RXBRK | ATMEL_US_OVRE | @@ -1200,7 +1212,8 @@ atmel_handle_receive(struct uart_port *port, unsigned int pending) if (pending & ATMEL_US_TIMEOUT) { atmel_uart_writel(port, ATMEL_US_IDR, ATMEL_US_TIMEOUT); - tasklet_schedule(&atmel_port->tasklet_rx); + atmel_tasklet_schedule(atmel_port, + &atmel_port->tasklet_rx); } } @@ -1230,7 +1243,7 @@ atmel_handle_transmit(struct uart_port *port, unsigned int pending) /* Either PDC or interrupt transmission */ atmel_uart_writel(port, ATMEL_US_IDR, atmel_port->tx_done_mask); - tasklet_schedule(&atmel_port->tasklet_tx); + atmel_tasklet_schedule(atmel_port, &atmel_port->tasklet_tx); } } @@ -1791,8 +1804,11 @@ static int atmel_startup(struct uart_port *port) return retval; } - tasklet_enable(&atmel_port->tasklet_rx); - tasklet_enable(&atmel_port->tasklet_tx); + atomic_set(&atmel_port->tasklet_shutdown, 0); + tasklet_init(&atmel_port->tasklet_rx, atmel_tasklet_rx_func, + (unsigned long)port); + tasklet_init(&atmel_port->tasklet_tx, atmel_tasklet_tx_func, + (unsigned long)port); /* * Initialize DMA (if necessary) @@ -1911,31 +1927,36 @@ static void atmel_shutdown(struct uart_port *port) { struct atmel_uart_port *atmel_port = to_atmel_uart_port(port); + /* Disable interrupts at device level */ + atmel_uart_writel(port, ATMEL_US_IDR, -1); + + /* Prevent spurious interrupts from scheduling the tasklet */ + atomic_inc(&atmel_port->tasklet_shutdown); + /* * Prevent any tasklets being scheduled during * cleanup */ del_timer_sync(&atmel_port->uart_timer); + /* Make sure that no interrupt is on the fly */ + synchronize_irq(port->irq); + /* * Clear out any scheduled tasklets before * we destroy the buffers */ - tasklet_disable(&atmel_port->tasklet_rx); - tasklet_disable(&atmel_port->tasklet_tx); tasklet_kill(&atmel_port->tasklet_rx); tasklet_kill(&atmel_port->tasklet_tx); /* * Ensure everything is stopped and - * disable all interrupts, port and break condition. + * disable port and break condition. */ atmel_stop_rx(port); atmel_stop_tx(port); atmel_uart_writel(port, ATMEL_US_CR, ATMEL_US_RSTSTA); - atmel_uart_writel(port, ATMEL_US_IDR, -1); - /* * Shut-down the DMA. @@ -2319,13 +2340,6 @@ static int atmel_init_port(struct atmel_uart_port *atmel_port, port->irq = pdev->resource[1].start; port->rs485_config = atmel_config_rs485; - tasklet_init(&atmel_port->tasklet_rx, atmel_tasklet_rx_func, - (unsigned long)port); - tasklet_init(&atmel_port->tasklet_tx, atmel_tasklet_tx_func, - (unsigned long)port); - tasklet_disable(&atmel_port->tasklet_rx); - tasklet_disable(&atmel_port->tasklet_tx); - memset(&atmel_port->rx_ring, 0, sizeof(atmel_port->rx_ring)); if (pdata && pdata->regs) { @@ -2710,6 +2724,7 @@ static int atmel_serial_probe(struct platform_device *pdev) atmel_port->uart.line = ret; atmel_serial_probe_fifos(atmel_port, pdev); + atomic_set(&port->tasklet_shutdown, 0); spin_lock_init(&atmel_port->lock_suspended); ret = atmel_init_port(atmel_port, pdev);