[Intel-gfx] [PATCH] drm: Include task->name and master status in debugfs clients info

[David Herrmann]

Hi

On Sat, Aug 9, 2014 at 8:22 AM, Chris Wilson <chris at chris-wilson.co.uk> wrote:
> Showing who is the current master is useful for trying to decypher
> errors when trying to acquire master (e.g. a race with X taking over
> from plymouth). By including the process name as well as the pid
> simplifies the task of grabbing enough information remotely at the point
> of error.
>
> Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> ---
>  drivers/gpu/drm/drm_info.c | 17 ++++++++++++-----
>  1 file changed, 12 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/gpu/drm/drm_info.c b/drivers/gpu/drm/drm_info.c
> index 15ec9f4..d813430 100644
> --- a/drivers/gpu/drm/drm_info.c
> +++ b/drivers/gpu/drm/drm_info.c
> @@ -184,14 +184,21 @@ int drm_clients_info(struct seq_file *m, void *data)
>         struct drm_file *priv;
>
>         mutex_lock(&dev->struct_mutex);
> -       seq_printf(m, "a dev    pid    uid      magic\n\n");
> -       list_for_each_entry(priv, &dev->filelist, lhead) {
> -               seq_printf(m, "%c %3d %5d %5d %10u\n",
> -                          priv->authenticated ? 'y' : 'n',
> -                          priv->minor->index,
> +       seq_printf(m, "                       pid dev master a   uid      magic\n");

Maybe mention "task" here? Or is this supposed to be a logical part of "pid"?

> +       list_for_each_entry_reverse(priv, &dev->filelist, lhead) {

No idea why you do backwards traversal, but ok..

> +               struct task_struct *task;
> +
> +               rcu_read_lock();

What's that rcu-lock for? task->comm is pre-allocated, priv->pid is
static, kuid... no idea?

Anyway, patch looks good otherwise. Especially task->comm sounds
really handy in that list.

Thanks
David

> +               task = pid_task(priv->pid, PIDTYPE_PID);
> +               seq_printf(m, "%20s %5d %3d   %c    %c %5d %10u\n",
> +                          task ? task->comm : "<unknown>",
>                            pid_vnr(priv->pid),
> +                          priv->minor->index,
> +                          priv->is_master ? 'y' : 'n',
> +                          priv->authenticated ? 'y' : 'n',
>                            from_kuid_munged(seq_user_ns(m), priv->uid),
>                            priv->magic);
> +               rcu_read_unlock();
>         }
>         mutex_unlock(&dev->struct_mutex);
>         return 0;
> --
> 1.9.1
>
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