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

[Tvrtko Ursulin]

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?

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);