On Thu, 2014-06-26 at 09:52 +0200, Samuel Iglesias Gonsálvez wrote:
> On Thu, 2014-06-26 at 09:46 +0200, Federico Vaga wrote:
> > 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 <federico.v...@cern.ch>
> > ---
> > 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)
>
> Acked-by: Samuel Iglesias Gonsalvez <sigles...@igalia.com>
>
> SamGreg, Would you mind picking this patch through your driver-core tree? Thanks, Sam
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