[PATCH 08/14] drm/amdkfd: Get reference to lead_thread task struct

[Oded Gabbay]

On Tue, Nov 28, 2017 at 1:29 AM, Felix Kuehling <Felix.Kuehling at amd.com> wrote:
> Increment the kfd_process.lead_thread's reference counter to make
> it safe to dereference. This is needed for getting a safe reference
> to the process' mm_struct.

I don't object to this patch, but I thought we don't dereference the
process' mm_struct...

>From kfd_priv.h:

/*
* Opaque pointer to mm_struct. We don't hold a reference to
* it so it should never be dereferenced from here. This is
* only used for looking up processes by their mm.
*/
void *mm;


>
> Signed-off-by: Felix Kuehling <Felix.Kuehling at amd.com>
> ---
>  drivers/gpu/drm/amd/amdkfd/kfd_process.c | 4 ++++
>  1 file changed, 4 insertions(+)
>
> diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_process.c b/drivers/gpu/drm/amd/amdkfd/kfd_process.c
> index 99c18ee..660d8bc 100644
> --- a/drivers/gpu/drm/amd/amdkfd/kfd_process.c
> +++ b/drivers/gpu/drm/amd/amdkfd/kfd_process.c
> @@ -24,6 +24,7 @@
>  #include <linux/log2.h>
>  #include <linux/sched.h>
>  #include <linux/sched/mm.h>
> +#include <linux/sched/task.h>
>  #include <linux/slab.h>
>  #include <linux/amd-iommu.h>
>  #include <linux/notifier.h>
> @@ -191,6 +192,8 @@ static void kfd_process_wq_release(struct work_struct *work)
>
>         mutex_destroy(&p->mutex);
>
> +       put_task_struct(p->lead_thread);
> +
>         kfree(p);
>
>         kfree(work);
> @@ -342,6 +345,7 @@ static struct kfd_process *create_process(const struct task_struct *thread)
>                         (uintptr_t)process->mm);
>
>         process->lead_thread = thread->group_leader;
> +       get_task_struct(process->lead_thread);
>
>         INIT_LIST_HEAD(&process->per_device_data);
>
> --
> 2.7.4
>