Messages in this thread | | | Subject | Re: [PATCH] ipoctal: protect only the real critical section | From | Samuel Iglesias Gonsálvez <> | Date | Thu, 26 Jun 2014 09:52:50 +0200 |
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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.vaga@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 <siglesias@igalia.com>
Sam [unhandled content-type:application/pgp-signature] | |