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Thu, 04 Mar 2021 17:23:16 +0100 Received: from euls16034.sgp.st.com (euls16034.sgp.st.com [10.75.44.20]) by beta.dmz-eu.st.com (STMicroelectronics) with ESMTP id A54A4100034; Thu, 4 Mar 2021 17:23:15 +0100 (CET) Received: from Webmail-eu.st.com (sfhdag2node3.st.com [10.75.127.6]) by euls16034.sgp.st.com (STMicroelectronics) with ESMTP id 98DCD20741B; Thu, 4 Mar 2021 17:23:15 +0100 (CET) Received: from localhost (10.75.127.51) by SFHDAG2NODE3.st.com (10.75.127.6) with Microsoft SMTP Server (TLS) id 15.0.1473.3; Thu, 4 Mar 2021 17:23:15 +0100 From: Erwan Le Ray To: Greg Kroah-Hartman , Jiri Slaby , Maxime Coquelin , Alexandre Torgue CC: , , , , Erwan Le Ray , Fabrice Gasnier , Valentin Caron Subject: [PATCH v2 05/13] serial: stm32: fix a deadlock condition with wakeup event Date: Thu, 4 Mar 2021 17:23:00 +0100 Message-ID: <20210304162308.8984-6-erwan.leray@foss.st.com> X-Mailer: git-send-email 2.17.1 In-Reply-To: <20210304162308.8984-1-erwan.leray@foss.st.com> References: <20210304162308.8984-1-erwan.leray@foss.st.com> MIME-Version: 1.0 X-Originating-IP: [10.75.127.51] X-ClientProxiedBy: SFHDAG3NODE2.st.com (10.75.127.8) To SFHDAG2NODE3.st.com (10.75.127.6) X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.369, 18.0.761 definitions=2021-03-04_05:2021-03-03, 2021-03-04 signatures=0 X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org Deadlock issue is seen when enabling CONFIG_PROVE_LOCKING=Y, and uart console as wakeup source. Deadlock occurs when resuming from low power mode if system is waked up via usart console. The deadlock is triggered 100% when also disabling console suspend prior to go to suspend. Simplified call stack, deadlock condition: - stm32_console_write <-- spin_lock already held - print_circular_bug - pm_wakeup_dev_event <-- triggers lockdep as seen above - stm32_receive_chars - stm32_interrupt <-- wakeup via uart console, takes the lock So, revisit spin_lock in stm32-usart driver: - there is no need to hold the lock to access ICR (atomic clear of status flags) - only hold the lock inside stm32_receive_chars() routine (no need to call pm_wakeup_dev_event with lock held) - keep stm32_transmit_chars() routine called with lock held Fixes: 48a6092fb41f ("serial: stm32-usart: Add STM32 USART Driver") Signed-off-by: Erwan Le Ray Signed-off-by: Fabrice Gasnier diff --git a/drivers/tty/serial/stm32-usart.c b/drivers/tty/serial/stm32-usart.c index 223cec70c57c..370141445780 100644 --- a/drivers/tty/serial/stm32-usart.c +++ b/drivers/tty/serial/stm32-usart.c @@ -214,13 +214,18 @@ static void stm32_usart_receive_chars(struct uart_port *port, bool threaded) struct tty_port *tport = &port->state->port; struct stm32_port *stm32_port = to_stm32_port(port); const struct stm32_usart_offsets *ofs = &stm32_port->info->ofs; - unsigned long c; + unsigned long c, flags; u32 sr; char flag; if (irqd_is_wakeup_set(irq_get_irq_data(port->irq))) pm_wakeup_event(tport->tty->dev, 0); + if (threaded) + spin_lock_irqsave(&port->lock, flags); + else + spin_lock(&port->lock); + while (stm32_usart_pending_rx(port, &sr, &stm32_port->last_res, threaded)) { sr |= USART_SR_DUMMY_RX; @@ -276,9 +281,12 @@ static void stm32_usart_receive_chars(struct uart_port *port, bool threaded) uart_insert_char(port, sr, USART_SR_ORE, c, flag); } - spin_unlock(&port->lock); + if (threaded) + spin_unlock_irqrestore(&port->lock, flags); + else + spin_unlock(&port->lock); + tty_flip_buffer_push(tport); - spin_lock(&port->lock); } static void stm32_usart_tx_dma_complete(void *arg) @@ -459,8 +467,6 @@ static irqreturn_t stm32_usart_interrupt(int irq, void *ptr) const struct stm32_usart_offsets *ofs = &stm32_port->info->ofs; u32 sr; - spin_lock(&port->lock); - sr = readl_relaxed(port->membase + ofs->isr); if ((sr & USART_SR_RTOF) && ofs->icr != UNDEF_REG) @@ -474,10 +480,11 @@ static irqreturn_t stm32_usart_interrupt(int irq, void *ptr) if ((sr & USART_SR_RXNE) && !(stm32_port->rx_ch)) stm32_usart_receive_chars(port, false); - if ((sr & USART_SR_TXE) && !(stm32_port->tx_ch)) + if ((sr & USART_SR_TXE) && !(stm32_port->tx_ch)) { + spin_lock(&port->lock); stm32_usart_transmit_chars(port); - - spin_unlock(&port->lock); + spin_unlock(&port->lock); + } if (stm32_port->rx_ch) return IRQ_WAKE_THREAD; @@ -490,13 +497,9 @@ 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); - spin_lock(&port->lock); - if (stm32_port->rx_ch) stm32_usart_receive_chars(port, true); - spin_unlock(&port->lock); - return IRQ_HANDLED; }