linux-kernel - [RFC PATCH 10/12] housekeeping: Affine unbound kthreads

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Date:   Wed, 23 Aug 2017 03:51:09 +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 10/12] housekeeping: Affine unbound kthreads

We want to be able to force the kthreads affinity when we'll repinplement
isolcpus= on top of housekeeping. Unfortunately many kthreads also
override their own affinity so we may need to revisit some of them.

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 | 1 +
 kernel/kthread.c             | 5 +++--
 2 files changed, 4 insertions(+), 2 deletions(-)

diff --git a/include/linux/housekeeping.h b/include/linux/housekeeping.h
index 0959601..2a9b808 100644
--- a/include/linux/housekeeping.h
+++ b/include/linux/housekeeping.h
@@ -11,6 +11,7 @@ enum hk_flags {
 	HK_FLAG_MISC		= (1 << 2),
 	HK_FLAG_SCHED		= (1 << 3),
 	HK_FLAG_WORKQUEUE	= (1 << 4),
+	HK_FLAG_KTHREAD		= (1 << 5),
 };
 
 #ifdef CONFIG_CPU_ISOLATION
diff --git a/kernel/kthread.c b/kernel/kthread.c
index 26db528..d4f1e63 100644
--- a/kernel/kthread.c
+++ b/kernel/kthread.c
@@ -21,6 +21,7 @@
 #include <linux/ptrace.h>
 #include <linux/uaccess.h>
 #include <linux/cgroup.h>
+#include <linux/housekeeping.h>
 #include <trace/events/sched.h>
 
 static DEFINE_SPINLOCK(kthread_create_lock);
@@ -317,7 +318,7 @@ struct task_struct *__kthread_create_on_node(int (*threadfn)(void *data),
 		 * The kernel thread should not inherit these properties.
 		 */
 		sched_setscheduler_nocheck(task, SCHED_NORMAL, &param);
-		set_cpus_allowed_ptr(task, cpu_all_mask);
+		set_cpus_allowed_ptr(task, housekeeping_cpumask(HK_FLAG_KTHREAD));
 	}
 	kfree(create);
 	return task;
@@ -536,7 +537,7 @@ int kthreadd(void *unused)
 	/* Setup a clean context for our children to inherit. */
 	set_task_comm(tsk, "kthreadd");
 	ignore_signals(tsk);
-	set_cpus_allowed_ptr(tsk, cpu_all_mask);
+	set_cpus_allowed_ptr(tsk, housekeeping_cpumask(HK_FLAG_KTHREAD));
 	set_mems_allowed(node_states[N_MEMORY]);
 
 	current->flags |= PF_NOFREEZE;
-- 
2.7.4