linux-kernel - [RFC PATCH 03/12] housekeeping: Provide a dynamic off-case to housekeeping_any

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Message-Id: <1503453071-952-4-git-send-email-fweisbec@gmail.com>
Date:   Wed, 23 Aug 2017 03:51:02 +0200
From:   Frederic Weisbecker <fweisbec@...il.com>
To:     LKML <linux-kernel@...r.kernel.org>
Cc:     Frederic Weisbecker <fweisbec@...il.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Chris Metcalf <cmetcalf@...lanox.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Luiz Capitulino <lcapitulino@...hat.com>,
        Christoph Lameter <cl@...ux.com>,
        "Paul E . McKenney" <paulmck@...ux.vnet.ibm.com>,
        Ingo Molnar <mingo@...nel.org>, Mike Galbraith <efault@....de>,
        Rik van Riel <riel@...hat.com>,
        Wanpeng Li <kernellwp@...il.com>
Subject: [RFC PATCH 03/12] housekeeping: Provide a dynamic off-case to housekeeping_any_cpu()

housekeeping_any_cpu() doesn't handle correctly the case where
CONFIG_NO_HZ_FULL=y and no CPU is in nohz_full mode. So far no caller
needs this but let's prepare to avoid any future surprise.

Signed-off-by: Frederic Weisbecker <fweisbec@...il.com>
Cc: Chris Metcalf <cmetcalf@...lanox.com>
Cc: Rik van Riel <riel@...hat.com>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: Mike Galbraith <efault@....de>
Cc: Ingo Molnar <mingo@...nel.org>
Cc: Christoph Lameter <cl@...ux.com>
Cc: Paul E. McKenney <paulmck@...ux.vnet.ibm.com>
Cc: Wanpeng Li <kernellwp@...il.com>
Cc: Luiz Capitulino <lcapitulino@...hat.com>
---
 include/linux/housekeeping.h | 21 ++++++++-------------
 1 file changed, 8 insertions(+), 13 deletions(-)

diff --git a/include/linux/housekeeping.h b/include/linux/housekeeping.h
index 3d6a8e6..64d0ee5 100644
--- a/include/linux/housekeeping.h
+++ b/include/linux/housekeeping.h
@@ -7,24 +7,19 @@
 
 #ifdef CONFIG_NO_HZ_FULL
 extern cpumask_var_t housekeeping_mask;
-
-static inline int housekeeping_any_cpu(void)
-{
-	return cpumask_any_and(housekeeping_mask, cpu_online_mask);
-}
-
 extern void __init housekeeping_init(void);
-
 #else
-
-static inline int housekeeping_any_cpu(void)
-{
-	return smp_processor_id();
-}
-
 static inline void housekeeping_init(void) { }
 #endif /* CONFIG_NO_HZ_FULL */
 
+static inline int housekeeping_any_cpu(void)
+{
+#ifdef CONFIG_NO_HZ_FULL
+	if (tick_nohz_full_enabled())
+		return cpumask_any_and(housekeeping_mask, cpu_online_mask);
+#endif
+	return smp_processor_id();
+}
 
 static inline const struct cpumask *housekeeping_cpumask(void)
 {
-- 
2.7.4