linux-kernel - [tip:sched/core] u64_stats: Introduce IRQs disabled helpers

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Message-ID: <tip-68107df5f2cb5dc3785be40162bfe2f19a178bbb@git.kernel.org>
Date:   Fri, 30 Sep 2016 05:05:25 -0700
From:   tip-bot for Frederic Weisbecker <tipbot@...or.com>
To:     linux-tip-commits@...r.kernel.org
Cc:     efault@....de, tglx@...utronix.de, fweisbec@...il.com,
        torvalds@...ux-foundation.org, peterz@...radead.org,
        riel@...hat.com, hpa@...or.com, eric.dumazet@...il.com,
        linux-kernel@...r.kernel.org, wanpeng.li@...mail.com,
        mingo@...nel.org, pbonzini@...hat.com
Subject: [tip:sched/core] u64_stats: Introduce IRQs disabled helpers

Commit-ID:  68107df5f2cb5dc3785be40162bfe2f19a178bbb
Gitweb:     http://git.kernel.org/tip/68107df5f2cb5dc3785be40162bfe2f19a178bbb
Author:     Frederic Weisbecker <fweisbec@...il.com>
AuthorDate: Mon, 26 Sep 2016 02:29:19 +0200
Committer:  Ingo Molnar <mingo@...nel.org>
CommitDate: Fri, 30 Sep 2016 11:46:40 +0200

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.

Signed-off-by: Frederic Weisbecker <fweisbec@...il.com>
Cc: Eric Dumazet <eric.dumazet@...il.com>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Mike Galbraith <efault@....de>
Cc: Paolo Bonzini <pbonzini@...hat.com>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Rik van Riel <riel@...hat.com>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: Wanpeng Li <wanpeng.li@...mail.com>
Link: http://lkml.kernel.org/r/1474849761-12678-4-git-send-email-fweisbec@gmail.com
Signed-off-by: Ingo Molnar <mingo@...nel.org>
---
 include/linux/u64_stats_sync.h | 45 ++++++++++++++++++++++--------------------
 1 file changed, 24 insertions(+), 21 deletions(-)

diff --git a/include/linux/u64_stats_sync.h b/include/linux/u64_stats_sync.h
index d3a2bb7..650f3dd 100644
--- a/include/linux/u64_stats_sync.h
+++ b/include/linux/u64_stats_sync.h
@@ -103,31 +103,42 @@ 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)
+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
-	preempt_disable();
-#endif
 	return 0;
 #endif
 }
 
-static inline bool u64_stats_fetch_retry(const struct u64_stats_sync *syncp,
+static inline unsigned int u64_stats_fetch_begin(const struct u64_stats_sync *syncp)
+{
+#if BITS_PER_LONG==32 && !defined(CONFIG_SMP)
+	preempt_disable();
+#endif
+	return __u64_stats_fetch_begin(syncp);
+}
+
+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
-	preempt_enable();
-#endif
 	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)
+	preempt_enable();
+#endif
+	return __u64_stats_fetch_retry(syncp, start);
+}
+
 /*
  * In case irq handlers can update u64 counters, readers can use following helpers
  * - SMP 32bit arches use seqcount protection, irq safe.
@@ -136,27 +147,19 @@ 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;
-#endif
+	return __u64_stats_fetch_begin(syncp);
 }
 
 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;
-#endif
+	return __u64_stats_fetch_retry(syncp, start);
 }
 
 #endif /* _LINUX_U64_STATS_SYNC_H */