net: u64_stats_sync improvements
- Add a comment about interrupts:
6) If counter might be written by an interrupt, readers should block
interrupts.
- Fix a typo in sample of use.
Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/linux/u64_stats_sync.h b/include/linux/u64_stats_sync.h
index d050515..b38e3a5 100644
--- a/include/linux/u64_stats_sync.h
+++ b/include/linux/u64_stats_sync.h
@@ -23,6 +23,10 @@
* pure reads. But if they have to fetch many values, it's better to not allow
* preemptions/interruptions to avoid many retries.
*
+ * 6) If counter might be written by an interrupt, readers should block interrupts.
+ * (On UP, there is no seqcount_t protection, a reader allowing interrupts could
+ * read partial values)
+ *
* Usage :
*
* Stats producer (writer) should use following template granted it already got
@@ -46,7 +50,7 @@
* start = u64_stats_fetch_begin(&stats->syncp);
* tbytes = stats->bytes64; // non atomic operation
* tpackets = stats->packets64; // non atomic operation
- * } while (u64_stats_fetch_retry(&stats->lock, syncp));
+ * } while (u64_stats_fetch_retry(&stats->syncp, start));
*
*
* Example of use in drivers/net/loopback.c, using per_cpu containers,