linux-kernel - [PATCH 3/4] scsi: scsi_dh_alua: WQ_PERCPU added to alloc

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20251031095643.74246-4-marco.crivellari@suse.com>
Date: Fri, 31 Oct 2025 10:56:42 +0100
From: Marco Crivellari <marco.crivellari@...e.com>
To: linux-kernel@...r.kernel.org,
	linux-scsi@...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>,
	"James E . J . Bottomley" <James.Bottomley@...senPartnership.com>,
	"Martin K . Petersen" <martin.petersen@...cle.com>
Subject: [PATCH 3/4] scsi: scsi_dh_alua: WQ_PERCPU added to alloc_workqueue users

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.

alloc_workqueue() treats all queues as per-CPU by default, while unbound
workqueues must opt-in via WQ_UNBOUND.

This default is suboptimal: most workloads benefit from unbound queues,
allowing the scheduler to place worker threads where they’re needed and
reducing noise when CPUs are isolated.

This change adds a new WQ_PERCPU flag to explicitly request
alloc_workqueue() to be per-cpu when WQ_UNBOUND has not been specified.

With the introduction of the WQ_PERCPU flag (equivalent to !WQ_UNBOUND),
any alloc_workqueue() caller that doesn’t explicitly specify WQ_UNBOUND
must now use WQ_PERCPU.

Once migration is complete, WQ_UNBOUND can be removed and unbound will
become the implicit default.

Suggested-by: Tejun Heo <tj@...nel.org>
Signed-off-by: Marco Crivellari <marco.crivellari@...e.com>
---
 drivers/scsi/device_handler/scsi_dh_alua.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/scsi/device_handler/scsi_dh_alua.c b/drivers/scsi/device_handler/scsi_dh_alua.c
index 1bf5948d1188..6fd89ae33059 100644
--- a/drivers/scsi/device_handler/scsi_dh_alua.c
+++ b/drivers/scsi/device_handler/scsi_dh_alua.c
@@ -1300,7 +1300,7 @@ static int __init alua_init(void)
 {
 	int r;

-	kaluad_wq = alloc_workqueue("kaluad", WQ_MEM_RECLAIM, 0);
+	kaluad_wq = alloc_workqueue("kaluad", WQ_MEM_RECLAIM | WQ_PERCPU, 0);
 	if (!kaluad_wq)
 		return -ENOMEM;

-- 
2.51.0