[dpdk-dev] Unsafe array accesses in rte_sched.c

[Stephen Hemminger]

On Fri, 16 Oct 2015 15:50:55 +0200
Simon Kågström <simon.kagstrom at netinsight.net> wrote:

> On 2015-10-16 15:39, Dumitrescu, Cristian wrote:
> >>         port->qsize_add[12] = port->qsize_add[11] + port->qsize[2];
> >>         port->qsize_add[13] = port->qsize_add[12] + port->qsize[3];
> >>         port->qsize_add[14] = port->qsize_add[13] + port->qsize[3];
> >>         port->qsize_add[15] = port->qsize_add[14] + port->qsize[3];
> >>
> >>         port->qsize_sum = port->qsize_add[15] + port->qsize[3];
> >>   }
> >>
> >> but port->qsize is actually defined as
> >>
> >>   uint16_t qsize[RTE_SCHED_TRAFFIC_CLASSES_PER_PIPE];
> >>
> > 
> > Not sure what you see "unsafe" here: qsize is an array of 4 elements, while qsize_add is a different array of 16 elements? Please explain.
> 
> Sorry, I should have been more explicit: What I mean that the code
> should loop over RTE_SCHED_TRAFFIC_CLASSES_PER_PIPE instead of
> hard-coding the numbers.
> 
> It certainly works with the current RTE_SCHED_TRAFFIC_CLASSES_PER_PIPE,
> but it would be safer (and in my opinion more clear) if it would not
> assume RTE_SCHED_TRAFFIC_CLASSES_PER_PIPE == 4.
> 
> // Simon

Unfortunately, current code has lots of hard wired assumptions about number
of traffic classes. Lots of manually loop unrolling etc. It would be better
if this was done using loops and telling compiler to unroll critical loops.