linux-kernel - [PATCH] usb: xhci: replace use of system_wq with system_percpu

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Message-ID: <20251106145428.250251-1-marco.crivellari@suse.com>
Date: Thu,  6 Nov 2025 15:54:28 +0100
From: Marco Crivellari <marco.crivellari@...e.com>
To: linux-kernel@...r.kernel.org,
	linux-usb@...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>,
	Mathias Nyman <mathias.nyman@...el.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: [PATCH] usb: xhci: replace use of system_wq with system_percpu_wq

Currently if a user enqueues 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 consistency cannot be addressed without refactoring the API.

This continues the effort to refactor workqueue APIs, which began with
the introduction of new workqueues and a new alloc_workqueue flag in:

commit 128ea9f6ccfb ("workqueue: Add system_percpu_wq and system_dfl_wq")
commit 930c2ea566af ("workqueue: Add new WQ_PERCPU flag")

Switch to using system_percpu_wq because system_wq is going away as part of
a workqueue restructuring.

Suggested-by: Tejun Heo <tj@...nel.org>
Signed-off-by: Marco Crivellari <marco.crivellari@...e.com>
---
 drivers/usb/host/xhci-dbgcap.c | 8 ++++----
 drivers/usb/host/xhci-ring.c   | 2 +-
 2 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/drivers/usb/host/xhci-dbgcap.c b/drivers/usb/host/xhci-dbgcap.c
index ecda964e018a..9da4f3b452cb 100644
--- a/drivers/usb/host/xhci-dbgcap.c
+++ b/drivers/usb/host/xhci-dbgcap.c
@@ -374,7 +374,7 @@ int dbc_ep_queue(struct dbc_request *req)
 		ret = dbc_ep_do_queue(req);
 	spin_unlock_irqrestore(&dbc->lock, flags);
 
-	mod_delayed_work(system_wq, &dbc->event_work, 0);
+	mod_delayed_work(system_percpu_wq, &dbc->event_work, 0);
 
 	trace_xhci_dbc_queue_request(req);
 
@@ -677,7 +677,7 @@ static int xhci_dbc_start(struct xhci_dbc *dbc)
 		return ret;
 	}
 
-	return mod_delayed_work(system_wq, &dbc->event_work,
+	return mod_delayed_work(system_percpu_wq, &dbc->event_work,
 				msecs_to_jiffies(dbc->poll_interval));
 }
 
@@ -1023,7 +1023,7 @@ static void xhci_dbc_handle_events(struct work_struct *work)
 		return;
 	}
 
-	mod_delayed_work(system_wq, &dbc->event_work,
+	mod_delayed_work(system_percpu_wq, &dbc->event_work,
 			 msecs_to_jiffies(poll_interval));
 }
 
@@ -1274,7 +1274,7 @@ static ssize_t dbc_poll_interval_ms_store(struct device *dev,
 
 	dbc->poll_interval = value;
 
-	mod_delayed_work(system_wq, &dbc->event_work, 0);
+	mod_delayed_work(system_percpu_wq, &dbc->event_work, 0);
 
 	return size;
 }
diff --git a/drivers/usb/host/xhci-ring.c b/drivers/usb/host/xhci-ring.c
index 8e209aa33ea7..3d05734c8377 100644
--- a/drivers/usb/host/xhci-ring.c
+++ b/drivers/usb/host/xhci-ring.c
@@ -434,7 +434,7 @@ void xhci_ring_cmd_db(struct xhci_hcd *xhci)
 
 static bool xhci_mod_cmd_timer(struct xhci_hcd *xhci)
 {
-	return mod_delayed_work(system_wq, &xhci->cmd_timer,
+	return mod_delayed_work(system_percpu_wq, &xhci->cmd_timer,
 			msecs_to_jiffies(xhci->current_cmd->timeout_ms));
 }
 
-- 
2.51.1