- 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@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
* (On UP, there is no seqcount_t protection, a reader allowing interrupts could
* read partial values)
*
* (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
* Usage :
*
* Stats producer (writer) should use following template granted it already got
*/
#include <linux/seqlock.h>
*/
#include <linux/seqlock.h>
-#if BITS_PER_LONG==32 && defined(CONFIG_SMP)
+#if BITS_PER_LONG==32 && defined(CONFIG_SMP)
};
static void inline u64_stats_update_begin(struct u64_stats_sync *syncp)
{
};
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);
write_seqcount_begin(&syncp->seq);
}
static void inline u64_stats_update_end(struct u64_stats_sync *syncp)
{
}
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);
write_seqcount_end(&syncp->seq);
}
static unsigned int inline u64_stats_fetch_begin(const struct u64_stats_sync *syncp)
{
}
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);
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)
{
}
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);
return read_seqcount_retry(&syncp->seq, start);
-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
-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,
+#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
#endif /* _LINUX_U64_STATS_SYNC_H */
#endif /* _LINUX_U64_STATS_SYNC_H */