Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755515AbaFZHvp (ORCPT ); Thu, 26 Jun 2014 03:51:45 -0400 Received: from cernmx13.cern.ch ([188.184.36.46]:51850 "EHLO CERNMX13.cern.ch" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754668AbaFZHvo (ORCPT ); Thu, 26 Jun 2014 03:51:44 -0400 X-Greylist: delayed 311 seconds by postgrey-1.27 at vger.kernel.org; Thu, 26 Jun 2014 03:51:43 EDT From: Federico Vaga To: , , CC: , , Federico Vaga Subject: [PATCH] ipoctal: protect only the real critical section Date: Thu, 26 Jun 2014 09:46:24 +0200 Message-ID: <1403768784-21605-1-git-send-email-federico.vaga@cern.ch> X-Mailer: git-send-email 1.7.10.4 MIME-Version: 1.0 Content-Type: text/plain X-Originating-IP: [137.138.193.223] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org In some conditions (echo or particular sequence of special characters), on buffer push, the tty layer calls the write operation while we are holding the spinlock. This means deadlock within the same process on kernels version < 3.12. It seems not a problem on recent kernel, but the patch still valid as locking optimization. The protected variables by the spinlock are: xmit_buf, nb_bytes, pointer_read and pointer_write. So, this patch reduces the locked area in the IRQ handler only to these variables. Most of the code inside the locked area in the IRQ handler is not protected elsewhere; it means that it is not protected at all. Signed-off-by: Federico Vaga --- drivers/ipack/devices/ipoctal.c | 5 ++--- 1 file changed, 2 insertions(+), 3 deletions(-) diff --git a/drivers/ipack/devices/ipoctal.c b/drivers/ipack/devices/ipoctal.c index 141094e..69687f1 100644 --- a/drivers/ipack/devices/ipoctal.c +++ b/drivers/ipack/devices/ipoctal.c @@ -177,19 +177,20 @@ static void ipoctal_irq_tx(struct ipoctal_channel *channel) if (channel->nb_bytes == 0) return; + spin_lock(&channel->lock); value = channel->tty_port.xmit_buf[*pointer_write]; iowrite8(value, &channel->regs->w.thr); channel->stats.tx++; (*pointer_write)++; *pointer_write = *pointer_write % PAGE_SIZE; channel->nb_bytes--; + spin_unlock(&channel->lock); } static void ipoctal_irq_channel(struct ipoctal_channel *channel) { u8 isr, sr; - spin_lock(&channel->lock); /* The HW is organized in pair of channels. See which register we need * to read from */ isr = ioread8(&channel->block_regs->r.isr); @@ -213,8 +214,6 @@ static void ipoctal_irq_channel(struct ipoctal_channel *channel) /* TX of each character */ if ((isr & channel->isr_tx_rdy_mask) && (sr & SR_TX_READY)) ipoctal_irq_tx(channel); - - spin_unlock(&channel->lock); } static irqreturn_t ipoctal_irq_handler(void *arg) -- 1.7.10.4 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/