Re: [PATCH v2 6/8] vdpa_sim: use kthread worker

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On Thu, Mar 02, 2023 at 04:30:04PM +0100, Simon Horman wrote:
On Thu, Mar 02, 2023 at 12:34:19PM +0100, Stefano Garzarella wrote:
Let's use our own kthread to run device jobs.
This allows us more flexibility, especially we can attach the kthread
to the user address space when vDPA uses user's VA.

Signed-off-by: Stefano Garzarella <sgarzare@xxxxxxxxxx>
 drivers/vdpa/vdpa_sim/vdpa_sim.h |  3 ++-
 drivers/vdpa/vdpa_sim/vdpa_sim.c | 17 ++++++++++++-----
 2 files changed, 14 insertions(+), 6 deletions(-)

diff --git a/drivers/vdpa/vdpa_sim/vdpa_sim.h b/drivers/vdpa/vdpa_sim/vdpa_sim.h
index acee20faaf6a..ce83f9130a5d 100644
--- a/drivers/vdpa/vdpa_sim/vdpa_sim.h
+++ b/drivers/vdpa/vdpa_sim/vdpa_sim.h
@@ -57,7 +57,8 @@ struct vdpasim_dev_attr {
 struct vdpasim {
 	struct vdpa_device vdpa;
 	struct vdpasim_virtqueue *vqs;
-	struct work_struct work;
+	struct kthread_worker *worker;
+	struct kthread_work work;
 	struct vdpasim_dev_attr dev_attr;
 	/* spinlock to synchronize virtqueue state */
 	spinlock_t lock;
diff --git a/drivers/vdpa/vdpa_sim/vdpa_sim.c b/drivers/vdpa/vdpa_sim/vdpa_sim.c
index a6ee830efc38..6feb29726c2a 100644
--- a/drivers/vdpa/vdpa_sim/vdpa_sim.c
+++ b/drivers/vdpa/vdpa_sim/vdpa_sim.c
@@ -11,8 +11,8 @@
 #include <linux/module.h>
 #include <linux/device.h>
 #include <linux/kernel.h>
+#include <linux/kthread.h>
 #include <linux/slab.h>
-#include <linux/sched.h>
 #include <linux/dma-map-ops.h>
 #include <linux/vringh.h>
 #include <linux/vdpa.h>
@@ -116,7 +116,7 @@ static void vdpasim_do_reset(struct vdpasim *vdpasim)
 static const struct vdpa_config_ops vdpasim_config_ops;
 static const struct vdpa_config_ops vdpasim_batch_config_ops;

-static void vdpasim_work_fn(struct work_struct *work)
+static void vdpasim_work_fn(struct kthread_work *work)
 	struct vdpasim *vdpasim = container_of(work, struct vdpasim, work);

@@ -159,7 +159,13 @@ struct vdpasim *vdpasim_create(struct vdpasim_dev_attr *dev_attr,

 	vdpasim = vdpa_to_sim(vdpa);
 	vdpasim->dev_attr = *dev_attr;
-	INIT_WORK(&vdpasim->work, vdpasim_work_fn);
+	kthread_init_work(&vdpasim->work, vdpasim_work_fn);
+	vdpasim->worker = kthread_create_worker(0, "vDPA sim worker: %s",
+						dev_attr->name);
+	if (IS_ERR(vdpasim->worker))
+		goto err_iommu;

Branching to err_iommu will result in a call to put_device(dev)...

Good catch!


... but dev is not initialised until the line following this hunk,
which is:

	dev = &vdpasim->;

In order to avoid leaking dev I _think_ the correct approach
is to move the initialisation of dev above the branch to
err_iommu, perhaps above the call to kthread_init_work()
is a good place.

Yep, I agree. I'll fix in v3.


This does move the assignment outside the locks above.
But I _think_ that is ok.

@@ -212,7 +218,7 @@ EXPORT_SYMBOL_GPL(vdpasim_create);

 void vdpasim_schedule_work(struct vdpasim *vdpasim)
-	schedule_work(&vdpasim->work);
+	kthread_queue_work(vdpasim->worker, &vdpasim->work);

@@ -612,7 +618,8 @@ static void vdpasim_free(struct vdpa_device *vdpa)
 	struct vdpasim *vdpasim = vdpa_to_sim(vdpa);
 	int i;

-	cancel_work_sync(&vdpasim->work);
+	kthread_cancel_work_sync(&vdpasim->work);
+	kthread_destroy_worker(vdpasim->worker);

 	for (i = 0; i < vdpasim->dev_attr.nvqs; i++) {

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