From mboxrd@z Thu Jan 1 00:00:00 1970 From: Loic Poulain Subject: [PATCHv2] serial: 8250: Fix thread unsafe __dma_tx_complete function Date: Thu, 24 Apr 2014 11:34:48 +0200 Message-ID: <1398332088-4905-1-git-send-email-loic.poulain@intel.com> Return-path: Received: from mga09.intel.com ([134.134.136.24]:17561 "EHLO mga09.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752412AbaDXJfc (ORCPT ); Thu, 24 Apr 2014 05:35:32 -0400 Sender: linux-serial-owner@vger.kernel.org List-Id: linux-serial@vger.kernel.org To: gregkh@linuxfoundation.org, heikki.krogerus@linux.intel.com Cc: linux-serial@vger.kernel.org, Loic Poulain __dma_tx_complete is not protected against concurrent call of serial8250_tx_dma. it can lead to circular tail index corruption or parallel call of serial_tx_dma on the same data portion. This patch fixes this issue by holding the port lock. Signed-off-by: Loic Poulain --- v2: extend lock to protect xmit tail (cf doc) and tx_running. tx_running and tail have to be updated atomically. update commit message. drivers/tty/serial/8250/8250_dma.c | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-) diff --git a/drivers/tty/serial/8250/8250_dma.c b/drivers/tty/serial/8250/8250_dma.c index 7046769..ab9096d 100644 --- a/drivers/tty/serial/8250/8250_dma.c +++ b/drivers/tty/serial/8250/8250_dma.c @@ -20,12 +20,15 @@ static void __dma_tx_complete(void *param) struct uart_8250_port *p = param; struct uart_8250_dma *dma = p->dma; struct circ_buf *xmit = &p->port.state->xmit; - - dma->tx_running = 0; + unsigned long flags; dma_sync_single_for_cpu(dma->txchan->device->dev, dma->tx_addr, UART_XMIT_SIZE, DMA_TO_DEVICE); + spin_lock_irqsave(&p->port.lock, flags); + + dma->tx_running = 0; + xmit->tail += dma->tx_size; xmit->tail &= UART_XMIT_SIZE - 1; p->port.icount.tx += dma->tx_size; @@ -35,6 +38,8 @@ static void __dma_tx_complete(void *param) if (!uart_circ_empty(xmit) && !uart_tx_stopped(&p->port)) serial8250_tx_dma(p); + + spin_unlock_irqrestore(&p->port.lock, flags); } static void __dma_rx_complete(void *param) -- 1.8.3.2