bpf: smp_wmb before bpf_ringbuf really commit #7993
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To guarantee visibility of writing ringbuffer,it is necessary
to call smp_wmb before ringbuffer really commit.
for instance, when updating the data of buffer in cpu1,
it is not visible for the cpu2 which may be accessing buffer. This may
lead to the consumer accessing a incorrect data. using the smp_wmb
before commmit will guarantee that the consume can access the correct data.
CPU1:
struct mem_event_t* data = bpf_ringbuf_reserve();
data->type = MEM_EVENT_KSWAPD_WAKE;
data->event_data.kswapd_wake.node_id = args->nid;
bpf_ringbuf_commit(data);
CPU2:
cons_pos = smp_load_acquire(r->consumer_pos);
len_ptr = r->data + (cons_pos & r->mask);
sample = (void *)len_ptr + BPF_RINGBUF_HDR_SZ;
access to sample
Signed-off-by: zhongjinji <[email protected]>
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Pull request for series with
subject: bpf: smp_wmb before bpf_ringbuf really commit
version: 1
url: https://patchwork.kernel.org/project/netdevbpf/list/?series=904951