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Date: Thu, 24 Jun 2010 12:54:06 +0200
From: Eric Dumazet <eric.dumazet@...il.com>
To: David Miller <davem@...emloft.net>
Cc: netdev <netdev@...r.kernel.org>
Subject: [PATCH net-next-2.6 2/4] net: u64_stats_fetch_begin_bh() and
u64_stats_fetch_retry_bh()
- Must disable preemption in case of 32bit UP in u64_stats_fetch_begin()
and u64_stats_fetch_retry()
- Add new u64_stats_fetch_begin_bh() and u64_stats_fetch_retry_bh() for
network usage, disabling BH on 32bit UP only.
Signed-off-by: Eric Dumazet <eric.dumazet@...il.com>
---
include/linux/u64_stats_sync.h | 59 +++++++++++++++++++++++--------
1 file changed, 44 insertions(+), 15 deletions(-)
diff --git a/include/linux/u64_stats_sync.h b/include/linux/u64_stats_sync.h
index 201d319..00c1592 100644
--- a/include/linux/u64_stats_sync.h
+++ b/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 */
--
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