Re: [Outreachy kernel] [PATCH] staging: nvec: Avoid the use of BUG_ON

[Laura Garcia <nevola@gmail.com>]

On Sun, Feb 21, 2016 at 07:31:12AM -0500, Julia Lawall wrote:
> On Sun, 21 Feb 2016, Laura Garcia Liebana wrote:
> 
> > Prevent a kernel panic by avoiding the use of the BUG_ON macro and using the
> > WARN_ON macro instead. Checkpatch detected this issue.
> 
> Why is nvec->state = 0; the right thing to do?  What will happen when the
> break is taken?
> 
> julia
> 
> > Signed-off-by: Laura Garcia Liebana <nevola@gmail.com>
> > ---
> >  drivers/staging/nvec/nvec.c | 14 ++++++++++++--
> >  1 file changed, 12 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/staging/nvec/nvec.c b/drivers/staging/nvec/nvec.c
> > index c335ae2..3b5b94f 100644
> > --- a/drivers/staging/nvec/nvec.c
> > +++ b/drivers/staging/nvec/nvec.c
> > @@ -641,11 +641,21 @@ static irqreturn_t nvec_interrupt(int irq, void *dev)
> >  			nvec_msg_free(nvec, nvec->rx);
> >  			nvec->state = 3;
> >  			nvec_tx_set(nvec);
> > -			BUG_ON(nvec->tx->size < 1);
> > +			if (WARN_ON(nvec->tx->size < 1)) {
> > +				dev_err(nvec->dev,
> > +					"Invalid TX size\n");
> > +				nvec->state = 0;
> > +				break;
> > +			}
> >  			to_send = nvec->tx->data[0];
> >  			nvec->tx->pos = 1;
> >  		} else if (status == (I2C_SL_IRQ)) {
> > -			BUG_ON(nvec->rx == NULL);
> > +			if (WARN_ON(!nvec->rx)) {
> > +				dev_err(nvec->dev,
> > +					"Invalid RX\n");
> > +				nvec->state = 0;
> > +				break;
> > +			}
> >  			nvec->rx->data[1] = received;
> >  			nvec->rx->pos = 2;
> >  			nvec->state = 4;
> > --
> > 2.7.0
> >
> > --
> > You received this message because you are subscribed to the Google Groups "outreachy-kernel" group.
> > To unsubscribe from this group and stop receiving emails from it, send an email to outreachy-kernel+unsubscribe@googlegroups.com.
> > To post to this group, send email to outreachy-kernel@googlegroups.com.
> > To view this discussion on the web visit https://groups.google.com/d/msgid/outreachy-kernel/20160221081553.GA4327%40sonyv.
> > For more options, visit https://groups.google.com/d/optout.
> >
I got inspired by an earlier case, for example in case 1:

nvec->rx = nvec_msg_alloc(nvec, NVEC_MSG_RX);
/* Should not happen in a normal world */
if (unlikely(!nvec->rx)) {
        nvec->state = 0;
        break;
}

A similar case appears in the case 2 (same function):

if (nvec->rx->data[0] != 0x01) {
        dev_err(nvec->dev,
                "Read without prior read command\n");
        nvec->state = 0;
        break;
}

Please let me know your thoughts about it.
Kind Regards.