linux-kernel - [PATCH 2/8] workqueue: Decouple HK_FLAG_WQ and HK_FLAG

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Date:   Fri,  4 Feb 2022 14:04:27 +0100
From:   Frederic Weisbecker <frederic@...nel.org>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Frederic Weisbecker <frederic@...nel.org>,
        Tejun Heo <tj@...nel.org>, Christoph Lameter <cl@...two.de>,
        Juri Lelli <juri.lelli@...hat.com>,
        Alex Belits <abelits@...vell.com>,
        Nitesh Lal <nilal@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Paul Gortmaker <paul.gortmaker@...driver.com>,
        Nicolas Saenz <nsaenzju@...hat.com>,
        "Paul E . McKenney" <paulmck@...nel.org>,
        Phil Auld <pauld@...hat.com>,
        Marcelo Tosatti <mtosatti@...hat.com>,
        Zefan Li <lizefan.x@...edance.com>
Subject: [PATCH 2/8] workqueue: Decouple HK_FLAG_WQ and HK_FLAG_DOMAIN cpumask fetch

To prepare for supporting each feature of the housekeeping cpumask
toward cpuset, prepare each of the HK_FLAG_* entries to move to their
own cpumask with enforcing to fetch them individually. The new
constraint is that multiple HK_FLAG_* entries can't be mixed together
anymore in a single call to housekeeping cpumask().

This will later allow, for example, to runtime modify the cpulist passed
through "isolcpus=", "nohz_full=" and "rcu_nocbs=" kernel boot
parameters.

Reviewed-by: Juri Lelli <juri.lelli@...hat.com>
Reviewed-by: Phil Auld <pauld@...hat.com>
Acked-by: Tejun Heo <tj@...nel.org>
Signed-off-by: Frederic Weisbecker <frederic@...nel.org>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: Juri Lelli <juri.lelli@...hat.com>
Cc: Marcelo Tosatti <mtosatti@...hat.com>
Cc: Nitesh Lal <nilal@...hat.com>
Cc: Nicolas Saenz <nsaenzju@...hat.com>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Christoph Lameter <cl@...two.de>
Cc: Tejun Heo <tj@...nel.org>
Cc: Zefan Li <lizefan.x@...edance.com>
Cc: Alex Belits <abelits@...vell.com>
Cc: Paul Gortmaker <paul.gortmaker@...driver.com>
Cc: Paul E. McKenney  <paulmck@...nel.org>
---
 kernel/workqueue.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index 33f1106b4f99..61ed310621ea 100644
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -6006,13 +6006,13 @@ static void __init wq_numa_init(void)
 void __init workqueue_init_early(void)
 {
 	int std_nice[NR_STD_WORKER_POOLS] = { 0, HIGHPRI_NICE_LEVEL };
-	int hk_flags = HK_FLAG_DOMAIN | HK_FLAG_WQ;
 	int i, cpu;
 
 	BUILD_BUG_ON(__alignof__(struct pool_workqueue) < __alignof__(long long));
 
 	BUG_ON(!alloc_cpumask_var(&wq_unbound_cpumask, GFP_KERNEL));
-	cpumask_copy(wq_unbound_cpumask, housekeeping_cpumask(hk_flags));
+	cpumask_copy(wq_unbound_cpumask, housekeeping_cpumask(HK_FLAG_WQ));
+	cpumask_and(wq_unbound_cpumask, wq_unbound_cpumask, housekeeping_cpumask(HK_FLAG_DOMAIN));
 
 	pwq_cache = KMEM_CACHE(pool_workqueue, SLAB_PANIC);
 
-- 
2.25.1