Hi Jerin,
>
> Hi Konstantin,
>
> > +/*
> > + * Marks given callback as used by datapath.
> > + */
> > +static __rte_always_inline void
> > +bpf_eth_cbi_inuse(struct bpf_eth_cbi *cbi)
> > +{
> > + cbi->use++;
> > + /* make sure no store/load reordering could happen */
> > + rte_smp_mb();
> > +}
> > +
> > +/*
> > + * Marks given callback list as not used by datapath.
> > + */
> > +static __rte_always_inline void
> > +bpf_eth_cbi_unuse(struct bpf_eth_cbi *cbi)
> > +{
> > + /* make sure all previous loads are completed */
> > + rte_smp_rmb();
>
> We earlier discussed this barrier. Will following scheme works out to
> fix the bpf_eth_cbi_wait() without cbi->use scheme?
>
> #ie. We need to exit from jitted or interpreted code irrespective of its
> state. IMO, We can do that by an _arch_ specific function to fill jitted
> memory with
> "exit" opcode(value:0x95, exit, return r0),so that above code needs to be
> come out i n anycase,
> on next instruction execution. I know, jitted memory is read-only in your
> design, I think, we can change the permission to "write" to the fill
> "exit" opcode(both jitted or interpreted case) for termination.
>
> What you think?
Not sure I understand your proposal...
Are you suggesting to change bpf_exec() and bpf_jit() to make them execute sync
primitives in an arch specific manner?
But some users probably will use bpf_exec/jitted program in the environment
that wouldn't require such synchronization.
For these people it would be just unnecessary slowdown.
If you are looking for a ways to replace 'smp_rmb' in bpf_eth_cbi_unuse() with
something arch specific, then
I can make cbi_inuse/cbi_unuse - arch specific with keeping current
implementation as generic one.
Would that help?
Konstantin
>
> > + cbi->use++;
> > +}
> > +
> > +/*
> > + * Waits till datapath finished using given callback.
> > + */
> > +static void
> > +bpf_eth_cbi_wait(const struct bpf_eth_cbi *cbi)
> > +{
> > + uint32_t nuse, puse;
> > +
> > + /* make sure all previous loads and stores are completed */
> > + rte_smp_mb();
> > +
> > + puse = cbi->use;
> > +
> > + /* in use, busy wait till current RX/TX iteration is finished */
> > + if ((puse & BPF_ETH_CBI_INUSE) != 0) {
> > + do {
> > + rte_pause();
> > + rte_compiler_barrier();
> > + nuse = cbi->use;
> > + } while (nuse == puse);
> > + }
> > +}
