Re: [PATCH 1/2] ixgbe: remove static qualifier for thread safety

[Bruce Richardson <bruce.richardson-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>]

On Thu, Oct 23, 2014 at 08:43:39AM +0900, Masaru Oki wrote:
> Hi,
> 
> in this code, pointer of local variable (mb_def) is returned by your changes.
> mb_def should be static for each thread.

Actually, no. A copy is made of 8 bytes of the mb_def variable and stored as 
an mbuf initializer inside the rxq structure. No use of the memory occupied 
by mb_def is made outside of the function, so the value does not need to be 
static.

/Bruce
> 
> 2014-10-22 19:55 GMT+09:00 Bruce Richardson <bruce.richardson-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>:
> > Remove the "static" prefix to the template mbuf variable in
> > ixgbe_rxq_vec_setup function. This will then allow different
> > threads to initialize different RX queues at the same time,
> > without one overwriting the other's data.
> >
> > Signed-off-by: Bruce Richardson <bruce.richardson-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>
> > ---
> >  lib/librte_pmd_ixgbe/ixgbe_rxtx_vec.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/lib/librte_pmd_ixgbe/ixgbe_rxtx_vec.c b/lib/librte_pmd_ixgbe/ixgbe_rxtx_vec.c
> > index a0d3d78..e813e43 100644
> > --- a/lib/librte_pmd_ixgbe/ixgbe_rxtx_vec.c
> > +++ b/lib/librte_pmd_ixgbe/ixgbe_rxtx_vec.c
> > @@ -730,7 +730,7 @@ static struct ixgbe_txq_ops vec_txq_ops = {
> >  int
> >  ixgbe_rxq_vec_setup(struct igb_rx_queue *rxq)
> >  {
> > -       static struct rte_mbuf mb_def = {
> > +       struct rte_mbuf mb_def = {
> >                 .nb_segs = 1,
> >                 .data_off = RTE_PKTMBUF_HEADROOM,
> >  #ifdef RTE_MBUF_REFCNT
> > --
> > 1.9.3
> >