Re: [RFC 2/3] drm/msm: Rework get_comm_cmdline() helper

[Rob Clark]

On Tue, Apr 18, 2023 at 1:34 AM Daniel Vetter <daniel@xxxxxxxx> wrote:
>
> On Tue, Apr 18, 2023 at 09:27:49AM +0100, Tvrtko Ursulin wrote:
> >
> > On 17/04/2023 21:12, Rob Clark wrote:
> > > From: Rob Clark <robdclark@xxxxxxxxxxxx>
> > >
> > > Make it work in terms of ctx so that it can be re-used for fdinfo.
> > >
> > > Signed-off-by: Rob Clark <robdclark@xxxxxxxxxxxx>
> > > ---
> > >   drivers/gpu/drm/msm/adreno/adreno_gpu.c |  4 ++--
> > >   drivers/gpu/drm/msm/msm_drv.c           |  2 ++
> > >   drivers/gpu/drm/msm/msm_gpu.c           | 13 ++++++-------
> > >   drivers/gpu/drm/msm/msm_gpu.h           | 12 ++++++++++--
> > >   drivers/gpu/drm/msm/msm_submitqueue.c   |  1 +
> > >   5 files changed, 21 insertions(+), 11 deletions(-)
> > >
> > > diff --git a/drivers/gpu/drm/msm/adreno/adreno_gpu.c b/drivers/gpu/drm/msm/adreno/adreno_gpu.c
> > > index bb38e728864d..43c4e1fea83f 100644
> > > --- a/drivers/gpu/drm/msm/adreno/adreno_gpu.c
> > > +++ b/drivers/gpu/drm/msm/adreno/adreno_gpu.c
> > > @@ -412,7 +412,7 @@ int adreno_set_param(struct msm_gpu *gpu, struct msm_file_private *ctx,
> > >             /* Ensure string is null terminated: */
> > >             str[len] = '\0';
> > > -           mutex_lock(&gpu->lock);
> > > +           mutex_lock(&ctx->lock);
> > >             if (param == MSM_PARAM_COMM) {
> > >                     paramp = &ctx->comm;
> > > @@ -423,7 +423,7 @@ int adreno_set_param(struct msm_gpu *gpu, struct msm_file_private *ctx,
> > >             kfree(*paramp);
> > >             *paramp = str;
> > > -           mutex_unlock(&gpu->lock);
> > > +           mutex_unlock(&ctx->lock);
> > >             return 0;
> > >     }
> > > diff --git a/drivers/gpu/drm/msm/msm_drv.c b/drivers/gpu/drm/msm/msm_drv.c
> > > index 3d73b98d6a9c..ca0e89e46e13 100644
> > > --- a/drivers/gpu/drm/msm/msm_drv.c
> > > +++ b/drivers/gpu/drm/msm/msm_drv.c
> > > @@ -581,6 +581,8 @@ static int context_init(struct drm_device *dev, struct drm_file *file)
> > >     rwlock_init(&ctx->queuelock);
> > >     kref_init(&ctx->ref);
> > > +   ctx->pid = get_pid(task_pid(current));
> >
> > Would it simplify things for msm if DRM core had an up to date file->pid as
> > proposed in
> > https://patchwork.freedesktop.org/patch/526752/?series=109902&rev=4 ? It
> > gets updated if ioctl issuer is different than fd opener and this being
> > context_init here reminded me of it. Maybe you wouldn't have to track the
> > pid in msm?

The problem is that we also need this for gpu devcore dumps, which
could happen after the drm_file is closed.  The ctx can outlive the
file.

But the ctx->pid has the same problem as the existing file->pid when
it comes to Xorg.. hopefully over time that problem just goes away.  I
guess I could do a similar dance to your patch to update the pid
whenever (for ex) a submitqueue is created.

> Can we go one step further and let the drm fdinfo stuff print these new
> additions? Consistency across drivers and all that.

Hmm, I guess I could _also_ store the overridden comm/cmdline in
drm_file.  I still need to track it in ctx (msm_file_private) because
I could need it after the file is closed.

Maybe it could be useful to have a gl extension to let the app set a
name on the context so that this is useful beyond native-ctx (ie.
maybe it would be nice to see that "chrome: lwn.net" is using less gpu
memory than "chrome: phoronix.com", etc)

BR,
-R

> Also for a generic trigger I think any driver ioctl is good enough (we
> only really need to avoid the auth dance when you're not on a render
> node).
> -Daniel
>
> >
> > Regards,
> >
> > Tvrtko
> >
> > > +   mutex_init(&ctx->lock);
> > >     msm_submitqueue_init(dev, ctx);
> > >     ctx->aspace = msm_gpu_create_private_address_space(priv->gpu, current);
> > > diff --git a/drivers/gpu/drm/msm/msm_gpu.c b/drivers/gpu/drm/msm/msm_gpu.c
> > > index c403912d13ab..f0f4f845c32d 100644
> > > --- a/drivers/gpu/drm/msm/msm_gpu.c
> > > +++ b/drivers/gpu/drm/msm/msm_gpu.c
> > > @@ -327,18 +327,17 @@ find_submit(struct msm_ringbuffer *ring, uint32_t fence)
> > >   static void retire_submits(struct msm_gpu *gpu);
> > > -static void get_comm_cmdline(struct msm_gem_submit *submit, char **comm, char **cmd)
> > > +static void get_comm_cmdline(struct msm_file_private *ctx, char **comm, char **cmd)
> > >   {
> > > -   struct msm_file_private *ctx = submit->queue->ctx;
> > >     struct task_struct *task;
> > > -   WARN_ON(!mutex_is_locked(&submit->gpu->lock));
> > > -
> > >     /* Note that kstrdup will return NULL if argument is NULL: */
> > > +   mutex_lock(&ctx->lock);
> > >     *comm = kstrdup(ctx->comm, GFP_KERNEL);
> > >     *cmd  = kstrdup(ctx->cmdline, GFP_KERNEL);
> > > +   mutex_unlock(&ctx->lock);
> > > -   task = get_pid_task(submit->pid, PIDTYPE_PID);
> > > +   task = get_pid_task(ctx->pid, PIDTYPE_PID);
> > >     if (!task)
> > >             return;
> > > @@ -372,7 +371,7 @@ static void recover_worker(struct kthread_work *work)
> > >             if (submit->aspace)
> > >                     submit->aspace->faults++;
> > > -           get_comm_cmdline(submit, &comm, &cmd);
> > > +           get_comm_cmdline(submit->queue->ctx, &comm, &cmd);
> > >             if (comm && cmd) {
> > >                     DRM_DEV_ERROR(dev->dev, "%s: offending task: %s (%s)\n",
> > > @@ -460,7 +459,7 @@ static void fault_worker(struct kthread_work *work)
> > >             goto resume_smmu;
> > >     if (submit) {
> > > -           get_comm_cmdline(submit, &comm, &cmd);
> > > +           get_comm_cmdline(submit->queue->ctx, &comm, &cmd);
> > >             /*
> > >              * When we get GPU iova faults, we can get 1000s of them,
> > > diff --git a/drivers/gpu/drm/msm/msm_gpu.h b/drivers/gpu/drm/msm/msm_gpu.h
> > > index 7a4fa1b8655b..b2023a42116b 100644
> > > --- a/drivers/gpu/drm/msm/msm_gpu.h
> > > +++ b/drivers/gpu/drm/msm/msm_gpu.h
> > > @@ -377,17 +377,25 @@ struct msm_file_private {
> > >      */
> > >     int sysprof;
> > > +   /** @pid: Process that opened this file. */
> > > +   struct pid *pid;
> > > +
> > > +   /**
> > > +    * lock: Protects comm and cmdline
> > > +    */
> > > +   struct mutex lock;
> > > +
> > >     /**
> > >      * comm: Overridden task comm, see MSM_PARAM_COMM
> > >      *
> > > -    * Accessed under msm_gpu::lock
> > > +    * Accessed under msm_file_private::lock
> > >      */
> > >     char *comm;
> > >     /**
> > >      * cmdline: Overridden task cmdline, see MSM_PARAM_CMDLINE
> > >      *
> > > -    * Accessed under msm_gpu::lock
> > > +    * Accessed under msm_file_private::lock
> > >      */
> > >     char *cmdline;
> > > diff --git a/drivers/gpu/drm/msm/msm_submitqueue.c b/drivers/gpu/drm/msm/msm_submitqueue.c
> > > index 0e803125a325..0444ba04fa06 100644
> > > --- a/drivers/gpu/drm/msm/msm_submitqueue.c
> > > +++ b/drivers/gpu/drm/msm/msm_submitqueue.c
> > > @@ -61,6 +61,7 @@ void __msm_file_private_destroy(struct kref *kref)
> > >     }
> > >     msm_gem_address_space_put(ctx->aspace);
> > > +   put_pid(ctx->pid);
> > >     kfree(ctx->comm);
> > >     kfree(ctx->cmdline);
> > >     kfree(ctx);
>
> --
> Daniel Vetter
> Software Engineer, Intel Corporation
> http://blog.ffwll.ch