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authorEric Dumazet <edumazet@google.com>2019-11-08 03:27:20 +0300
committerDavid S. Miller <davem@davemloft.net>2019-11-08 07:03:08 +0300
commit316580b69d0a7aeeee5063af47438b626bc47cbd (patch)
tree83ede594937ec2ce27335a73fb3d6cea4ef95909 /include/linux/u64_stats_sync.h
parent4a43b1f96b1d94adcd296b2ff80d7294f82a9dc9 (diff)
downloadlinux-316580b69d0a7aeeee5063af47438b626bc47cbd.tar.xz
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 <edumazet@google.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'include/linux/u64_stats_sync.h')
-rw-r--r--include/linux/u64_stats_sync.h51
1 files 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 <asm/local64.h>
+
+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)
{