linux-kernel - [PATCH 2/2] s390: replace use of system_wq with system_percpu

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Message-ID: <20250905090857.108240-3-marco.crivellari@suse.com>
Date: Fri,  5 Sep 2025 11:08:57 +0200
From: Marco Crivellari <marco.crivellari@...e.com>
To: linux-kernel@...r.kernel.org,
	linux-s390@...r.kernel.org
Cc: Tejun Heo <tj@...nel.org>,
	Lai Jiangshan <jiangshanlai@...il.com>,
	Frederic Weisbecker <frederic@...nel.org>,
	Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
	Marco Crivellari <marco.crivellari@...e.com>,
	Michal Hocko <mhocko@...e.com>,
	Alexander Gordeev <agordeev@...ux.ibm.com>,
	Vasily Gorbik <gor@...ux.ibm.com>,
	Heiko Carstens <hca@...ux.ibm.com>
Subject: [PATCH 2/2] s390: replace use of system_wq with system_percpu_wq

Currently if a user enqueue a work item using schedule_delayed_work() the
used wq is "system_wq" (per-cpu wq) while queue_delayed_work() use
WORK_CPU_UNBOUND (used when a cpu is not specified). The same applies to
schedule_work() that is using system_wq and queue_work(), that makes use
again of WORK_CPU_UNBOUND.

This lack of consistentcy cannot be addressed without refactoring the API.

system_wq is a per-CPU worqueue, yet nothing in its name tells about that
CPU affinity constraint, which is very often not required by users. Make
it clear by adding a system_percpu_wq.

queue_work() / queue_delayed_work() mod_delayed_work() will now use the
new per-cpu wq: whether the user still stick on the old name a warn will
be printed along a wq redirect to the new one.

This patch add the new system_percpu_wq except for mm, fs and net
subsystem, whom are handled in separated patches.

The old wq will be kept for a few release cylces.

Suggested-by: Tejun Heo <tj@...nel.org>
Signed-off-by: Marco Crivellari <marco.crivellari@...e.com>
---
 arch/s390/kernel/diag/diag324.c  | 4 ++--
 arch/s390/kernel/hiperdispatch.c | 2 +-
 2 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/arch/s390/kernel/diag/diag324.c b/arch/s390/kernel/diag/diag324.c
index 7fa4c0b7eb6c..f0a8b4841fb9 100644
--- a/arch/s390/kernel/diag/diag324.c
+++ b/arch/s390/kernel/diag/diag324.c
@@ -116,7 +116,7 @@ static void pibwork_handler(struct work_struct *work)
 	mutex_lock(&pibmutex);
 	timedout = ktime_add_ns(data->expire, PIBWORK_DELAY);
 	if (ktime_before(ktime_get(), timedout)) {
-		mod_delayed_work(system_wq, &pibwork, nsecs_to_jiffies(PIBWORK_DELAY));
+		mod_delayed_work(system_percpu_wq, &pibwork, nsecs_to_jiffies(PIBWORK_DELAY));
 		goto out;
 	}
 	vfree(data->pib);
@@ -174,7 +174,7 @@ long diag324_pibbuf(unsigned long arg)
 		pib_update(data);
 		data->sequence++;
 		data->expire = ktime_add_ns(ktime_get(), tod_to_ns(data->pib->intv));
-		mod_delayed_work(system_wq, &pibwork, nsecs_to_jiffies(PIBWORK_DELAY));
+		mod_delayed_work(system_percpu_wq, &pibwork, nsecs_to_jiffies(PIBWORK_DELAY));
 		first = false;
 	}
 	rc = data->rc;
diff --git a/arch/s390/kernel/hiperdispatch.c b/arch/s390/kernel/hiperdispatch.c
index e7b66d046e8d..85b5508ab62c 100644
--- a/arch/s390/kernel/hiperdispatch.c
+++ b/arch/s390/kernel/hiperdispatch.c
@@ -191,7 +191,7 @@ int hd_enable_hiperdispatch(void)
 		return 0;
 	if (hd_online_cores <= hd_entitled_cores)
 		return 0;
-	mod_delayed_work(system_wq, &hd_capacity_work, HD_DELAY_INTERVAL * hd_delay_factor);
+	mod_delayed_work(system_percpu_wq, &hd_capacity_work, HD_DELAY_INTERVAL * hd_delay_factor);
 	hd_update_capacities();
 	return 1;
 }
-- 
2.51.0