From 968d04e8de53789ccdb9f74413eb497f155d266b Mon Sep 17 00:00:00 2001 From: Federico Vaga Date: Thu, 26 Jun 2014 09:46:24 +0200 Subject: ipoctal: protect only the real critical section 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 Acked-by: Samuel Iglesias Gonsalvez Signed-off-by: Greg Kroah-Hartman --- 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 141094e7c06e..69687f156999 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) -- cgit v1.2.3