bpf: Use u64_stats_t in struct bpf_prog_stats

Commit 316580b69d0a ("u64_stats: provide u64_stats_t type")
fixed possible load/store tearing on 64bit arches.

For instance the following C code

stats->nsecs += sched_clock() - start;

Could be rightfully implemented like this by a compiler,
confusing concurrent readers a lot:

stats->nsecs += sched_clock();
// arbitrary delay
stats->nsecs -= start;

Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20211026214133.3114279-4-eric.dumazet@gmail.com

1 files changed, 3 insertions, 3 deletions

diff --git a/kernel/bpf/trampoline.c b/kernel/bpf/trampoline.c
index e5963de368ed..e98de5e73ba5 100644
--- a/kernel/bpf/trampoline.c
+++ b/kernel/bpf/trampoline.c
@@ -545,7 +545,7 @@ static void notrace inc_misses_counter(struct bpf_prog *prog)
 
 	stats = this_cpu_ptr(prog->stats);
 	u64_stats_update_begin(&stats->syncp);
-	stats->misses++;
+	u64_stats_inc(&stats->misses);
 	u64_stats_update_end(&stats->syncp);
 }
 
@@ -590,8 +590,8 @@ static void notrace update_prog_stats(struct bpf_prog *prog,
 
 		stats = this_cpu_ptr(prog->stats);
 		flags = u64_stats_update_begin_irqsave(&stats->syncp);
-		stats->cnt++;
-		stats->nsecs += sched_clock() - start;
+		u64_stats_inc(&stats->cnt);
+		u64_stats_add(&stats->nsecs, sched_clock() - start);
 		u64_stats_update_end_irqrestore(&stats->syncp, flags);
 	}
 }