Re: [Intel-gfx] [PATCH 10/24] drm: Remove drm_pending_event->pid

Sean Paul
2017-03-13T17:05:27Z

On Wed, Mar 08, 2017 at 03:12:43PM +0100, Daniel Vetter wrote:
> We might as well dump the drm_file pointer, that's about as useful
> a cookie as the pid. Noticed while typing docs for drm_file and friends.
>
> Since the only consumer of this is the tracepoints I think we can safely
> change this - those tracepoints should not be uapi relevant at all. It
> all goes back to
>
> commit b9c2c9ae882f058084e13e339925dbf8d2d20271
> Author: Jesse Barnes <jbarnes@virtuousgeek.org>
> Date: Thu Jul 1 16:48:09 2010 -0700
>
> drm: add per-event vblank event trace points
>
> which doesn't give a special justification for using pid over a pointer.

Well, it's friendlier to look at, I suppose.

>
> Also note that the nouveau code setting it is entirely pointless:
> Since this isn't a vblank event, it will never hit the vblank
> tracepoints.
>
> Cc: Ben Skeggs <bskeggs@redhat.com>
> Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
> ---
> drivers/gpu/drm/drm_irq.c | 5 ++---
> drivers/gpu/drm/drm_trace.h | 20 ++++++++++----------
> drivers/gpu/drm/nouveau/nouveau_usif.c | 1 -
> include/drm/drm_file.h | 2 --
> 4 files changed, 12 insertions(+), 16 deletions(-)
>
> diff --git a/drivers/gpu/drm/drm_irq.c b/drivers/gpu/drm/drm_irq.c
> index 1906723af389..9bdca69f754c 100644
> --- a/drivers/gpu/drm/drm_irq.c
> +++ b/drivers/gpu/drm/drm_irq.c
> @@ -978,7 +978,7 @@ static void send_vblank_event(struct drm_device *dev,
> e->event.tv_sec = now->tv_sec;
> e->event.tv_usec = now->tv_usec;
>
> - trace_drm_vblank_event_delivered(e->base.pid, e->pipe,
> + trace_drm_vblank_event_delivered(e->base.file_priv, e->pipe,
> e->event.sequence);
>
> drm_send_event_locked(dev, &e->base);
> @@ -1505,7 +1505,6 @@ static int drm_queue_vblank_event(struct drm_device *dev, unsigned int pipe,
> }
>
> e->pipe = pipe;
> - e->base.pid = current->pid;

Do you think it would be worthwhile to output the pid:file_priv mapping here in
case someone is using pid?

Regardless, the code looks correct, and I don't any skin in this game, so I'll
add my R-b and let you decide what to do if no one else complains.

Reviewed-by: Sean Paul <seanpaul@chromium.org>

> e->event.base.type = DRM_EVENT_VBLANK;
> e->event.base.length = sizeof(e->event);
> e->event.user_data = vblwait->request.signal;
> @@ -1534,7 +1533,7 @@ static int drm_queue_vblank_event(struct drm_device *dev, unsigned int pipe,
> DRM_DEBUG("event on vblank count %u, current %u, crtc %u\n",
> vblwait->request.sequence, seq, pipe);
>
> - trace_drm_vblank_event_queued(current->pid, pipe,
> + trace_drm_vblank_event_queued(file_priv, pipe,
> vblwait->request.sequence);
>
> e->event.sequence = vblwait->request.sequence;
> diff --git a/drivers/gpu/drm/drm_trace.h b/drivers/gpu/drm/drm_trace.h
> index ce3c42813fbb..14c5a777682e 100644
> --- a/drivers/gpu/drm/drm_trace.h
> +++ b/drivers/gpu/drm/drm_trace.h
> @@ -24,36 +24,36 @@ TRACE_EVENT(drm_vblank_event,
> );
>
> TRACE_EVENT(drm_vblank_event_queued,
> - TP_PROTO(pid_t pid, int crtc, unsigned int seq),
> - TP_ARGS(pid, crtc, seq),
> + TP_PROTO(struct drm_file *file, int crtc, unsigned int seq),
> + TP_ARGS(file, crtc, seq),
> TP_STRUCT__entry(
> - __field(pid_t, pid)
> + __field(struct drm_file *, file)
> __field(int, crtc)
> __field(unsigned int, seq)
> ),
> TP_fast_assign(
> - __entry->pid = pid;
> + __entry->file = file;
> __entry->crtc = crtc;
> __entry->seq = seq;
> ),
> - TP_printk("pid=%d, crtc=%d, seq=%u", __entry->pid, __entry->crtc, \
> + TP_printk("file=%p, crtc=%d, seq=%u", __entry->file, __entry->crtc, \
> __entry->seq)
> );
>
> TRACE_EVENT(drm_vblank_event_delivered,
> - TP_PROTO(pid_t pid, int crtc, unsigned int seq),
> - TP_ARGS(pid, crtc, seq),
> + TP_PROTO(struct drm_file *file, int crtc, unsigned int seq),
> + TP_ARGS(file, crtc, seq),
> TP_STRUCT__entry(
> - __field(pid_t, pid)
> + __field(struct drm_file *, file)
> __field(int, crtc)
> __field(unsigned int, seq)
> ),
> TP_fast_assign(
> - __entry->pid = pid;
> + __entry->file = file;
> __entry->crtc = crtc;
> __entry->seq = seq;
> ),
> - TP_printk("pid=%d, crtc=%d, seq=%u", __entry->pid, __entry->crtc, \
> + TP_printk("file=%p, crtc=%d, seq=%u", __entry->file, __entry->crtc, \
> __entry->seq)
> );
>
> diff --git a/drivers/gpu/drm/nouveau/nouveau_usif.c b/drivers/gpu/drm/nouveau/nouveau_usif.c
> index afbdbed1a690..9dc10b17ad34 100644
> --- a/drivers/gpu/drm/nouveau/nouveau_usif.c
> +++ b/drivers/gpu/drm/nouveau/nouveau_usif.c
> @@ -211,7 +211,6 @@ usif_notify_get(struct drm_file *f, void *data, u32 size, void *argv, u32 argc)
> goto done;
> ntfy->p->base.event = &ntfy->p->e.base;
> ntfy->p->base.file_priv = f;
> - ntfy->p->base.pid = current->pid;
> ntfy->p->e.base.type = DRM_NOUVEAU_EVENT_NVIF;
> ntfy->p->e.base.length = sizeof(ntfy->p->e.base) + ntfy->reply;
>
> diff --git a/include/drm/drm_file.h b/include/drm/drm_file.h
> index d1a25cc17fd1..4e347399a7bd 100644
> --- a/include/drm/drm_file.h
> +++ b/include/drm/drm_file.h
> @@ -75,8 +75,6 @@ struct drm_pending_event {
> struct list_head link;
> struct list_head pending_link;
> struct drm_file *file_priv;
> - pid_t pid; /* pid of requester, no guarantee it's valid by the time
> - we deliver the event, for tracing only */
> };
>
> /** File private data */
> --
> 2.11.0
>
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