Re: [dpdk-dev] [PATCH] eal: fix check when retrieving current cpu affinity

["Burakov, Anatoly" <anatoly.burakov@intel.com>]

On 14-Feb-19 5:41 PM, David Marchand wrote:
> 
> 
> On Thu, Feb 14, 2019 at 5:44 PM Burakov, Anatoly 
> <anatoly.burakov@intel.com <mailto:anatoly.burakov@intel.com>> wrote:
> 
>     On 14-Feb-19 1:27 PM, David Marchand wrote:
>      > pthread_getaffinity_np returns a >0 value when failing.
>      >
>      > This is mainly for the sake of correctness.
>      > The only case where it could fail is when passing an incorrect cpuset
>      > size wrt to the kernel.
>      >
>      > Fixes: 2eba8d21f3c9 ("eal: restrict cores auto detection")
>      > Signed-off-by: David Marchand <david.marchand@redhat.com
>     <mailto:david.marchand@redhat.com>>
>      > ---
>      >   lib/librte_eal/common/eal_common_options.c | 5 ++---
>      >   1 file changed, 2 insertions(+), 3 deletions(-)
>      >
>      > diff --git a/lib/librte_eal/common/eal_common_options.c
>     b/lib/librte_eal/common/eal_common_options.c
>      > index 6c96f45..1f45f82 100644
>      > --- a/lib/librte_eal/common/eal_common_options.c
>      > +++ b/lib/librte_eal/common/eal_common_options.c
>      > @@ -1343,10 +1343,9 @@ static int xdigit2val(unsigned char c)
>      >       unsigned int lcore_id;
>      >       unsigned int removed = 0;
>      >       rte_cpuset_t affinity_set;
>      > -     pthread_t tid = pthread_self();
>      >
>      > -     if (pthread_getaffinity_np(tid, sizeof(rte_cpuset_t),
>      > -                             &affinity_set) < 0)
>      > +     if (pthread_getaffinity_np(pthread_self(),
>     sizeof(rte_cpuset_t),
>      > +                             &affinity_set))
>      >               CPU_ZERO(&affinity_set);
>      >
>      >       for (lcore_id = 0; lcore_id < RTE_MAX_LCORE; lcore_id++) {
>      >
>     CC: stable?
> 
> 
> Not really sure about CCing stable for this.
> 
> I did not get errors with pthread_getaffinity_np so far.
> Afaiu, it would need the kernel and libc to have different cpuset sizes.
> I did not investigate in which situations it could happen.
> 

You're incorrectly handling error condition - that's a bug regardless of 
how likely it is to occur :)

-- 
Thanks,
Anatoly