From 316580b69d0a7aeeee5063af47438b626bc47cbd Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Thu, 7 Nov 2019 16:27:20 -0800 Subject: [PATCH] u64_stats: provide u64_stats_t type On 64bit arches, struct u64_stats_sync is empty and provides no help against load/store tearing. Using READ_ONCE()/WRITE_ONCE() would be needed. But the update side would be slightly more expensive. local64_t was defined so that we could use regular adds in a manner which is atomic wrt IRQs. However the u64_stats infra means we do not have to use local64_t on 32bit arches since the syncp provides the needed protection. Signed-off-by: Eric Dumazet Signed-off-by: David S. Miller --- include/linux/u64_stats_sync.h | 51 +++++++++++++++++++++++++++++++--- 1 file changed, 47 insertions(+), 4 deletions(-) diff --git a/include/linux/u64_stats_sync.h b/include/linux/u64_stats_sync.h index a27604f99ed0..9de5c10293f5 100644 --- a/include/linux/u64_stats_sync.h +++ b/include/linux/u64_stats_sync.h @@ -40,8 +40,8 @@ * spin_lock_bh(...) or other synchronization to get exclusive access * ... * u64_stats_update_begin(&stats->syncp); - * stats->bytes64 += len; // non atomic operation - * stats->packets64++; // non atomic operation + * u64_stats_add(&stats->bytes64, len); // non atomic operation + * u64_stats_inc(&stats->packets64); // non atomic operation * u64_stats_update_end(&stats->syncp); * * While a consumer (reader) should use following template to get consistent @@ -52,8 +52,8 @@ * * do { * start = u64_stats_fetch_begin(&stats->syncp); - * tbytes = stats->bytes64; // non atomic operation - * tpackets = stats->packets64; // non atomic operation + * tbytes = u64_stats_read(&stats->bytes64); // non atomic operation + * tpackets = u64_stats_read(&stats->packets64); // non atomic operation * } while (u64_stats_fetch_retry(&stats->syncp, start)); * * @@ -68,6 +68,49 @@ struct u64_stats_sync { #endif }; +#if BITS_PER_LONG == 64 +#include + +typedef struct { + local64_t v; +} u64_stats_t ; + +static inline u64 u64_stats_read(const u64_stats_t *p) +{ + return local64_read(&p->v); +} + +static inline void u64_stats_add(u64_stats_t *p, unsigned long val) +{ + local64_add(val, &p->v); +} + +static inline void u64_stats_inc(u64_stats_t *p) +{ + local64_inc(&p->v); +} + +#else + +typedef struct { + u64 v; +} u64_stats_t; + +static inline u64 u64_stats_read(const u64_stats_t *p) +{ + return p->v; +} + +static inline void u64_stats_add(u64_stats_t *p, unsigned long val) +{ + p->v += val; +} + +static inline void u64_stats_inc(u64_stats_t *p) +{ + p->v++; +} +#endif static inline void u64_stats_init(struct u64_stats_sync *syncp) { -- 2.20.1