linux-kernel - [PATCH 11/12] housekeeping: Add basic isolcpus flags

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Date:   Fri,  1 Sep 2017 18:41:46 +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: [PATCH 11/12] housekeeping: Add basic isolcpus flags

Add flags to control nohz and domain isolations from "isolcpus=", in
order to centralize the isolation features to a common interface. Domain
isolation remains the default so not to break the existing isolcpus
boot paramater behaviour.

Further flags in the future may include 0hz (1hz tick offload) and timers,
workqueue, RCU, kthread, watchdog, likely all merged together in a
common flag ("async"?). In any case, this will have to be modifiable by
cpusets.

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>
---
 kernel/housekeeping.c | 26 +++++++++++++++++++++++++-
 1 file changed, 25 insertions(+), 1 deletion(-)

diff --git a/kernel/housekeeping.c b/kernel/housekeeping.c
index 5f0e7ec..6476e7c 100644
--- a/kernel/housekeeping.c
+++ b/kernel/housekeeping.c
@@ -10,6 +10,7 @@
 #include <linux/tick.h>
 #include <linux/init.h>
 #include <linux/static_key.h>
+#include <linux/ctype.h>
 
 DEFINE_STATIC_KEY_FALSE(housekeeping_overriden);
 EXPORT_SYMBOL_GPL(housekeeping_overriden);
@@ -119,6 +120,29 @@ __setup("nohz_full=", housekeeping_nohz_full_setup);
 
 static int __init housekeeping_isolcpus_setup(char *str)
 {
-	return housekeeping_setup(str, HK_FLAG_DOMAIN);
+	unsigned int flags = 0;
+
+	while (isalpha(*str)) {
+		if (!strncmp(str, "nohz,", 5)) {
+			str += 5;
+			flags |= HK_FLAG_TICK;
+			continue;
+		}
+
+		if (!strncmp(str, "domain,", 7)) {
+			str += 7;
+			flags |= HK_FLAG_DOMAIN;
+			continue;
+		}
+
+		pr_warn("isolcpus: Error, unknown flag\n");
+		return 0;
+	}
+
+	/* Default behaviour for isolcpus without flags */
+	if (!flags)
+		flags |= HK_FLAG_DOMAIN;
+
+	return housekeeping_setup(str, flags);
 }
 __setup("isolcpus=", housekeeping_isolcpus_setup);
-- 
2.7.4