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

Stefano Garzarella
2023-03-02T15:48:53Z

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@redhat.com>
>> ---
>> 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!

>
>> +
>> spin_lock_init(&vdpasim->lock);
>> spin_lock_init(&vdpasim->iommu_lock);
>
>... but dev is not initialised until the line following this hunk,
>which is:
>
> dev = &vdpasim->vdpa.dev;
>
>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.

Thanks,
Stefano

>
>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);
>> }
>> EXPORT_SYMBOL_GPL(vdpasim_schedule_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++) {
>> vringh_kiov_cleanup(&vdpasim->vqs[i].out_iov);
>> --
>> 2.39.2
>>
>