RDMA/core: 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@kernel.org>
Signed-off-by: Marco Crivellari <marco.crivellari@suse.com>
Link: https://patch.msgid.link/20251101163121.78400-3-marco.crivellari@suse.com
Signed-off-by: Leon Romanovsky <leon@kernel.org>

diff --git a/drivers/infiniband/core/cm.c b/drivers/infiniband/core/cm.c
index 2a36a9345959235db8fa6a9b58f5736184d8a1d5..024df6ee239d93e2cddd7940c1a53ea0ad5d7b71 100644 (file)
--- a/drivers/infiniband/core/cm.c
+++ b/drivers/infiniband/core/cm.c
@@ -4517,7 +4517,7 @@ static int __init ib_cm_init(void)
        get_random_bytes(&cm.random_id_operand, sizeof cm.random_id_operand);
        INIT_LIST_HEAD(&cm.timewait_list);
 
-       cm.wq = alloc_workqueue("ib_cm", 0, 1);
+       cm.wq = alloc_workqueue("ib_cm", WQ_PERCPU, 1);
        if (!cm.wq) {
                ret = -ENOMEM;
                goto error2;

diff --git a/drivers/infiniband/core/device.c b/drivers/infiniband/core/device.c
index b4f3c835844a922321442e364672926000989840..13e8a1714bbd7ff49af3c1a9bd83640c5e904dc2 100644 (file)
--- a/drivers/infiniband/core/device.c
+++ b/drivers/infiniband/core/device.c
@@ -3021,7 +3021,7 @@ static int __init ib_core_init(void)
 {
        int ret = -ENOMEM;
 
-       ib_wq = alloc_workqueue("infiniband", 0, 0);
+       ib_wq = alloc_workqueue("infiniband", WQ_PERCPU, 0);
        if (!ib_wq)
                return -ENOMEM;
 
@@ -3031,7 +3031,7 @@ static int __init ib_core_init(void)
                goto err;
 
        ib_comp_wq = alloc_workqueue("ib-comp-wq",
-                       WQ_HIGHPRI | WQ_MEM_RECLAIM | WQ_SYSFS, 0);
+                       WQ_HIGHPRI | WQ_MEM_RECLAIM | WQ_SYSFS | WQ_PERCPU, 0);
        if (!ib_comp_wq)
                goto err_unbound;