Re: [PATCH bpf-next 3/3] bpf, libbpf: use proper barriers in perf ring buffer walk
flat view
From: Peter Zijlstra <peterz@infradead.org>
Date: 2018-10-17 23:48:09
On Wed, Oct 17, 2018 at 04:41:56PM +0200, Daniel Borkmann wrote:
quoted hunk ↗ jump to hunk
+static __u64 bpf_perf_read_head(struct perf_event_mmap_page *header) +{ + __u64 data_head = READ_ONCE(header->data_head); + + smp_rmb(); + return data_head; +} + +static void bpf_perf_write_tail(struct perf_event_mmap_page *header, + __u64 data_tail) +{ + smp_mb(); + header->data_tail = data_tail; +}
Same coments, either smp_load_acquire()/smp_store_release() or at the very least a WRITE_ONCE() there.