---

yaml
---
r: 203194
b: refs/heads/master
c: 33d91f0
h: refs/heads/master
v: v3

[refs]

@@ -1,2 +1,2 @@
 ---
-refs/heads/master: 7a9b2d59507d85569b8a456688ef40cf2ac73e48
+refs/heads/master: 33d91f00c73ba0012bce18c1690cb8313ca7adaa

trunk/include/linux/u64_stats_sync.h

@@ -27,6 +27,9 @@
  *    (On UP, there is no seqcount_t protection, a reader allowing interrupts could
  *     read partial values)
  *
+ * 7) For softirq uses, readers can use u64_stats_fetch_begin_bh() and
+ *    u64_stats_fetch_retry_bh() helpers
+ *
  * Usage :
  *
  * Stats producer (writer) should use following template granted it already got
@@ -58,54 +61,80 @@
  */
 #include <linux/seqlock.h>
 
-#if BITS_PER_LONG==32 && defined(CONFIG_SMP)
 struct u64_stats_sync {
+#if BITS_PER_LONG==32 && defined(CONFIG_SMP)
 	seqcount_t	seq;
+#endif
 };
 
 static void inline u64_stats_update_begin(struct u64_stats_sync *syncp)
 {
+#if BITS_PER_LONG==32 && defined(CONFIG_SMP)
 	write_seqcount_begin(&syncp->seq);
+#endif
 }
 
 static void inline u64_stats_update_end(struct u64_stats_sync *syncp)
 {
+#if BITS_PER_LONG==32 && defined(CONFIG_SMP)
 	write_seqcount_end(&syncp->seq);
+#endif
 }
 
 static unsigned int inline u64_stats_fetch_begin(const struct u64_stats_sync *syncp)
 {
+#if BITS_PER_LONG==32 && defined(CONFIG_SMP)
 	return read_seqcount_begin(&syncp->seq);
+#else
+#if BITS_PER_LONG==32
+	preempt_disable();
+#endif
+	return 0;
+#endif
 }
 
 static bool inline u64_stats_fetch_retry(const struct u64_stats_sync *syncp,
 					 unsigned int start)
 {
+#if BITS_PER_LONG==32 && defined(CONFIG_SMP)
 	return read_seqcount_retry(&syncp->seq, start);
-}
-
 #else
-struct u64_stats_sync {
-};
-
-static void inline u64_stats_update_begin(struct u64_stats_sync *syncp)
-{
-}
-
-static void inline u64_stats_update_end(struct u64_stats_sync *syncp)
-{
+#if BITS_PER_LONG==32
+	preempt_enable();
+#endif
+	return false;
+#endif
 }
 
-static unsigned int inline u64_stats_fetch_begin(const struct u64_stats_sync *syncp)
+/*
+ * In case softirq handlers can update u64 counters, readers can use following helpers
+ * - SMP 32bit arches use seqcount protection, irq safe.
+ * - UP 32bit must disable BH.
+ * - 64bit have no problem atomically reading u64 values, irq safe.
+ */
+static unsigned int inline u64_stats_fetch_begin_bh(const struct u64_stats_sync *syncp)
 {
+#if BITS_PER_LONG==32 && defined(CONFIG_SMP)
+	return read_seqcount_begin(&syncp->seq);
+#else
+#if BITS_PER_LONG==32
+	local_bh_disable();
+#endif
 	return 0;
+#endif
 }
 
-static bool inline u64_stats_fetch_retry(const struct u64_stats_sync *syncp,
+static bool inline u64_stats_fetch_retry_bh(const struct u64_stats_sync *syncp,
 					 unsigned int start)
 {
+#if BITS_PER_LONG==32 && defined(CONFIG_SMP)
+	return read_seqcount_retry(&syncp->seq, start);
+#else
+#if BITS_PER_LONG==32
+	local_bh_enable();
+#endif
 	return false;
-}
 #endif
+}
 
 #endif /* _LINUX_U64_STATS_SYNC_H */