linux-kernel - [PATCH 3/5] u64_stats: Introduce IRQs disabled helpers

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Date:   Fri,  2 Sep 2016 16:03:03 +0200
From:   Frederic Weisbecker <fweisbec@...il.com>
To:     LKML <linux-kernel@...r.kernel.org>
Cc:     Frederic Weisbecker <fweisbec@...il.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Wanpeng Li <wanpeng.li@...mail.com>,
        Eric Dumazet <eric.dumazet@...il.com>,
        Ingo Molnar <mingo@...nel.org>, Mike Galbraith <efault@....de>,
        Rik van Riel <riel@...hat.com>
Subject: [PATCH 3/5] u64_stats: Introduce IRQs disabled helpers

Introduce light versions of u64_stats helpers for context where
either preempt or IRQs are disabled. This way we can make this library
usable by scheduler irqtime accounting which currenty implement its
ad-hoc version.

Cc: Rik van Riel <riel@...hat.com>
Cc: Paolo Bonzini <pbonzini@...hat.com>
Cc: Wanpeng Li <wanpeng.li@...mail.com>
Cc: Mike Galbraith <efault@....de>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Ingo Molnar <mingo@...nel.org>
Cc: Eric Dumazet <eric.dumazet@...il.com>
Signed-off-by: Frederic Weisbecker <fweisbec@...il.com>
---
 include/linux/u64_stats_sync.h | 55 ++++++++++++++++++++++++------------------
 1 file changed, 31 insertions(+), 24 deletions(-)

diff --git a/include/linux/u64_stats_sync.h b/include/linux/u64_stats_sync.h
index d3a2bb7..9101d23 100644
--- a/include/linux/u64_stats_sync.h
+++ b/include/linux/u64_stats_sync.h
@@ -103,28 +103,41 @@ static inline void u64_stats_update_end_raw(struct u64_stats_sync *syncp)
 #endif
 }
 
+static inline unsigned int __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
+	return 0;
+#endif
+}
+
 static inline unsigned int 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
+#if BITS_PER_LONG==32 && !defined(CONFIG_SMP)
 	preempt_disable();
+#else
+	return __u64_stats_fetch_begin(syncp);
 #endif
-	return 0;
+}
+
+static inline bool __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
+	return false;
 #endif
 }
 
 static inline bool 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
-#if BITS_PER_LONG==32
+#if BITS_PER_LONG==32 && !defined(CONFIG_SMP)
 	preempt_enable();
-#endif
-	return false;
+#else
+	return __u64_stats_fetch_retry(syncp, start);
 #endif
 }
 
@@ -136,26 +149,20 @@ static inline bool u64_stats_fetch_retry(const struct u64_stats_sync *syncp,
  */
 static inline unsigned int u64_stats_fetch_begin_irq(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
+#if BITS_PER_LONG==32 && !defined(CONFIG_SMP)
 	local_irq_disable();
-#endif
-	return 0;
+#else
+	return __u64_stats_fetch_begin(syncp);
 #endif
 }
 
 static inline bool u64_stats_fetch_retry_irq(const struct u64_stats_sync *syncp,
-					 unsigned int start)
+					     unsigned int start)
 {
-#if BITS_PER_LONG==32 && defined(CONFIG_SMP)
-	return read_seqcount_retry(&syncp->seq, start);
-#else
-#if BITS_PER_LONG==32
+#if BITS_PER_LONG==32 && !defined(CONFIG_SMP)
 	local_irq_enable();
-#endif
-	return false;
+#else
+	return __u64_stats_fetch_retry(syncp, start);
 #endif
 }
 
-- 
2.7.0