On 2/13/2024 11:10 AM, Eugenio Perez Martin wrote:
> On Mon, Feb 12, 2024 at 6:16 PM Steve Sistare <steven.sistare@xxxxxxxxxx> wrote:
>>
>> Flush to guarantee no workers are running when suspend returns.
>>
>> Signed-off-by: Steve Sistare <steven.sistare@xxxxxxxxxx>
>> ---
>> drivers/vdpa/vdpa_sim/vdpa_sim.c | 13 +++++++++++++
>> 1 file changed, 13 insertions(+)
>>
>> diff --git a/drivers/vdpa/vdpa_sim/vdpa_sim.c b/drivers/vdpa/vdpa_sim/vdpa_sim.c
>> index be2925d0d283..a662b90357c3 100644
>> --- a/drivers/vdpa/vdpa_sim/vdpa_sim.c
>> +++ b/drivers/vdpa/vdpa_sim/vdpa_sim.c
>> @@ -74,6 +74,17 @@ static void vdpasim_worker_change_mm_sync(struct vdpasim *vdpasim,
>> kthread_flush_work(work);
>> }
>>
>> +static void flush_work_fn(struct kthread_work *work) {}
>> +
>> +static void vdpasim_flush_work(struct vdpasim *vdpasim)
>> +{
>> + struct kthread_work work;
>> +
>> + kthread_init_work(&work, flush_work_fn);
>
> If the work is already queued, doesn't it break the linked list
> because of the memset in kthread_init_work?
work is a local variable. It completes before vdpasim_flush_work returns,
thus is never already queued on entry to vdpasim_flush_work.
Am I missing your point?
>> + kthread_queue_work(vdpasim->worker, &work);
>> + kthread_flush_work(&work);
>> +}
>> +
>> static struct vdpasim *vdpa_to_sim(struct vdpa_device *vdpa)
>> {
>> return container_of(vdpa, struct vdpasim, vdpa);
>> @@ -511,6 +522,8 @@ static int vdpasim_suspend(struct vdpa_device *vdpa)
>> vdpasim->running = false;
>> mutex_unlock(&vdpasim->mutex);
>>
>> + vdpasim_flush_work(vdpasim);
>
> Do we need to protect the case where vdpasim_kick_vq and
> vdpasim_suspend are called "at the same time"? Correct userland should
> not be doing it but buggy or mailious could be. Just calling
> vdpasim_flush_work with the mutex acquired would solve the issue,
> doesn't it?
Good catch. I need to serialize access to vdpasim->running plus the worker queue
in these two functions. vdpasim_kick_vq currently takes no locks. In case it is called
from non-task contexts, I should define a new spinlock to be acquired in both functions.
- Steve
