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libbpf, xsk: Add libbpf_smp_store_release libbpf_smp_load_acquire

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Now that the AF_XDP rings have load-acquire/store-release semantics,
move libbpf to that as well.

The library-internal libbpf_smp_{load_acquire,store_release} are only
valid for 32-bit words on ARM64.

Also, remove the barriers that are no longer in use.

Signed-off-by: Björn Töpel <bjorn.topel@intel.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Toke Høiland-Jørgensen <toke@redhat.com>
Link: https://lore.kernel.org/bpf/20210305094113.413544-3-bjorn.topel@gmail.com
This commit is contained in:
Björn Töpel
2021-03-05 10:41:13 +01:00
committed by Andrii Nakryiko
parent d64f8d3207
commit 1d483b45fc
2 changed files with 55 additions and 34 deletions
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17
src/xsk.h
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@@ -96,7 +96,8 @@ static inline __u32 xsk_prod_nb_free(struct xsk_ring_prod *r, __u32 nb)
* this function. Without this optimization it whould have been
* free_entries = r->cached_prod - r->cached_cons + r->size.
*/
r->cached_cons = *r->consumer + r->size;
r->cached_cons = libbpf_smp_load_acquire(r->consumer);
r->cached_cons += r->size;
return r->cached_cons - r->cached_prod;
}
@@ -106,7 +107,7 @@ static inline __u32 xsk_cons_nb_avail(struct xsk_ring_cons *r, __u32 nb)
__u32 entries = r->cached_prod - r->cached_cons;
if (entries == 0) {
r->cached_prod = *r->producer;
r->cached_prod = libbpf_smp_load_acquire(r->producer);
entries = r->cached_prod - r->cached_cons;
}
@@ -129,9 +130,7 @@ static inline void xsk_ring_prod__submit(struct xsk_ring_prod *prod, __u32 nb)
/* Make sure everything has been written to the ring before indicating
* this to the kernel by writing the producer pointer.
*/
libbpf_smp_wmb();
*prod->producer += nb;
libbpf_smp_store_release(prod->producer, *prod->producer + nb);
}
static inline __u32 xsk_ring_cons__peek(struct xsk_ring_cons *cons, __u32 nb, __u32 *idx)
@@ -139,11 +138,6 @@ static inline __u32 xsk_ring_cons__peek(struct xsk_ring_cons *cons, __u32 nb, __
__u32 entries = xsk_cons_nb_avail(cons, nb);
if (entries > 0) {
/* Make sure we do not speculatively read the data before
* we have received the packet buffers from the ring.
*/
libbpf_smp_rmb();
*idx = cons->cached_cons;
cons->cached_cons += entries;
}
@@ -161,9 +155,8 @@ static inline void xsk_ring_cons__release(struct xsk_ring_cons *cons, __u32 nb)
/* Make sure data has been read before indicating we are done
* with the entries by updating the consumer pointer.
*/
libbpf_smp_rwmb();
libbpf_smp_store_release(cons->consumer, *cons->consumer + nb);
*cons->consumer += nb;
}
static inline void *xsk_umem__get_data(void *umem_area, __u64 addr)