On Sat Jun 13, 2026 at 9:48 PM EDT, Tamir Duberstein wrote: > Consumer-side ring buffer code uses architecture-specific smp_* helpers > for shared memory accesses. > > Use compiler atomics instead. They provide equivalent acquire and > release ordering through a portable userspace interface and allow the > next commit to use compiler fences in the wakeup protocol without mixing > atomic interfaces. > > Assisted-by: Codex:gpt-5.5 > Signed-off-by: Tamir Duberstein <[email protected]>
Reviewed-by: Emil Tsalapatis <[email protected]> > --- > tools/lib/bpf/ringbuf.c | 20 +++++++++++--------- > 1 file changed, 11 insertions(+), 9 deletions(-) > > diff --git a/tools/lib/bpf/ringbuf.c b/tools/lib/bpf/ringbuf.c > index b7adce37b519..1c24a83f59d5 100644 > --- a/tools/lib/bpf/ringbuf.c > +++ b/tools/lib/bpf/ringbuf.c > @@ -264,13 +264,13 @@ static int64_t ringbuf_process_ring(struct ring *r, > size_t n) > if (n == 0) > return 0; > > - cons_pos = smp_load_acquire(r->consumer_pos); > + cons_pos = __atomic_load_n(r->consumer_pos, __ATOMIC_ACQUIRE); > do { > got_new_data = false; > - prod_pos = smp_load_acquire(r->producer_pos); > + prod_pos = __atomic_load_n(r->producer_pos, __ATOMIC_ACQUIRE); > while (cons_pos != prod_pos) { > len_ptr = r->data + (cons_pos & r->mask); > - len = smp_load_acquire(len_ptr); > + len = __atomic_load_n(len_ptr, __ATOMIC_ACQUIRE); > > /* sample not committed yet, bail out for now */ > if (len & BPF_RINGBUF_BUSY_BIT) > @@ -284,14 +284,16 @@ static int64_t ringbuf_process_ring(struct ring *r, > size_t n) > err = r->sample_cb(r->ctx, sample, len); > if (err < 0) { > /* update consumer pos and bail out */ > - smp_store_release(r->consumer_pos, > - cons_pos); > + __atomic_store_n(r->consumer_pos, > + cons_pos, > + __ATOMIC_RELEASE); > return err; > } > cnt++; > } > > - smp_store_release(r->consumer_pos, cons_pos); > + __atomic_store_n(r->consumer_pos, cons_pos, > + __ATOMIC_RELEASE); > > if (cnt >= n) > goto done; > @@ -406,8 +408,8 @@ struct ring *ring_buffer__ring(struct ring_buffer *rb, > unsigned int idx) > > unsigned long ring__consumer_pos(const struct ring *r) > { > - /* Synchronizes with smp_store_release() in ringbuf_process_ring(). */ > - return smp_load_acquire(r->consumer_pos); > + /* Synchronizes with the release store in ringbuf_process_ring(). */ > + return __atomic_load_n(r->consumer_pos, __ATOMIC_ACQUIRE); > } > > unsigned long ring__producer_pos(const struct ring *r) > @@ -415,7 +417,7 @@ unsigned long ring__producer_pos(const struct ring *r) > /* Synchronizes with smp_store_release() in __bpf_ringbuf_reserve() in > * the kernel. > */ > - return smp_load_acquire(r->producer_pos); > + return __atomic_load_n(r->producer_pos, __ATOMIC_ACQUIRE); > } > > size_t ring__avail_data_size(const struct ring *r)
