[PATCH 3/4] amd/amdkfd: WQ_PERCPU added to alloc_workqueue users

[Marco Crivellari <marco.crivellari@suse.com>]

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>
---
 drivers/gpu/drm/amd/amdkfd/kfd_process.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_process.c b/drivers/gpu/drm/amd/amdkfd/kfd_process.c
index ddfe30c13e9d..ebc9925f4e66 100644
--- a/drivers/gpu/drm/amd/amdkfd/kfd_process.c
+++ b/drivers/gpu/drm/amd/amdkfd/kfd_process.c
@@ -690,7 +690,8 @@ void kfd_procfs_del_queue(struct queue *q)
 int kfd_process_create_wq(void)
 {
 	if (!kfd_process_wq)
-		kfd_process_wq = alloc_workqueue("kfd_process_wq", 0, 0);
+		kfd_process_wq = alloc_workqueue("kfd_process_wq", WQ_PERCPU,
+						 0);
 	if (!kfd_restore_wq)
 		kfd_restore_wq = alloc_ordered_workqueue("kfd_restore_wq",
 							 WQ_FREEZABLE);
-- 
2.51.0