Re: [patch V2 16/29] drm: Simplify stacktrace handling

[Daniel Vetter]

On Thu, Apr 18, 2019 at 10:41:35AM +0200, Thomas Gleixner wrote:
> Replace the indirection through struct stack_trace by using the storage
> array based interfaces.
> 
> The original code in all printing functions is really wrong. It allocates a
> storage array on stack which is unused because depot_fetch_stack() does not
> store anything in it. It overwrites the entries pointer in the stack_trace
> struct so it points to the depot storage.

Thanks for cleaning this up for us!

> Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
> Cc: intel-gfx@xxxxxxxxxxxxxxxxxxxxx
> Cc: Joonas Lahtinen <joonas.lahtinen@xxxxxxxxxxxxxxx>
> Cc: Maarten Lankhorst <maarten.lankhorst@xxxxxxxxxxxxxxx>
> Cc: dri-devel@xxxxxxxxxxxxxxxxxxxxx
> Cc: David Airlie <airlied@xxxxxxxx>
> Cc: Jani Nikula <jani.nikula@xxxxxxxxxxxxxxx>
> Cc: Daniel Vetter <daniel@xxxxxxxx>
> Cc: Rodrigo Vivi <rodrigo.vivi@xxxxxxxxx>

Acked-by: Daniel Vetter <daniel.vetter@xxxxxxxx>

for merging through whatever tree is convenient for you (or tell me I
should pick it up into drm-next when the prep work landed).

Cheers, Daniel

> ---
>  drivers/gpu/drm/drm_mm.c                |   22 +++++++---------------
>  drivers/gpu/drm/i915/i915_vma.c         |   11 ++++-------
>  drivers/gpu/drm/i915/intel_runtime_pm.c |   21 +++++++--------------
>  3 files changed, 18 insertions(+), 36 deletions(-)
> 
> --- a/drivers/gpu/drm/drm_mm.c
> +++ b/drivers/gpu/drm/drm_mm.c
> @@ -106,22 +106,19 @@
>  static noinline void save_stack(struct drm_mm_node *node)
>  {
>  	unsigned long entries[STACKDEPTH];
> -	struct stack_trace trace = {
> -		.entries = entries,
> -		.max_entries = STACKDEPTH,
> -		.skip = 1
> -	};
> +	unsigned int n;
>  
> -	save_stack_trace(&trace);
> +	n = stack_trace_save(entries, ARRAY_SIZE(entries), 1);
>  
>  	/* May be called under spinlock, so avoid sleeping */
> -	node->stack = depot_save_stack(&trace, GFP_NOWAIT);
> +	node->stack = stack_depot_save(entries, n, GFP_NOWAIT);
>  }
>  
>  static void show_leaks(struct drm_mm *mm)
>  {
>  	struct drm_mm_node *node;
> -	unsigned long entries[STACKDEPTH];
> +	unsigned long *entries;
> +	unsigned int nr_entries;
>  	char *buf;
>  
>  	buf = kmalloc(BUFSZ, GFP_KERNEL);
> @@ -129,19 +126,14 @@ static void show_leaks(struct drm_mm *mm
>  		return;
>  
>  	list_for_each_entry(node, drm_mm_nodes(mm), node_list) {
> -		struct stack_trace trace = {
> -			.entries = entries,
> -			.max_entries = STACKDEPTH
> -		};
> -
>  		if (!node->stack) {
>  			DRM_ERROR("node [%08llx + %08llx]: unknown owner\n",
>  				  node->start, node->size);
>  			continue;
>  		}
>  
> -		depot_fetch_stack(node->stack, &trace);
> -		snprint_stack_trace(buf, BUFSZ, &trace, 0);
> +		nr_entries = stack_depot_fetch(node->stack, &entries);
> +		stack_trace_snprint(buf, BUFSZ, entries, nr_entries, 0);
>  		DRM_ERROR("node [%08llx + %08llx]: inserted at\n%s",
>  			  node->start, node->size, buf);
>  	}
> --- a/drivers/gpu/drm/i915/i915_vma.c
> +++ b/drivers/gpu/drm/i915/i915_vma.c
> @@ -36,11 +36,8 @@
>  
>  static void vma_print_allocator(struct i915_vma *vma, const char *reason)
>  {
> -	unsigned long entries[12];
> -	struct stack_trace trace = {
> -		.entries = entries,
> -		.max_entries = ARRAY_SIZE(entries),
> -	};
> +	unsigned long *entries;
> +	unsigned int nr_entries;
>  	char buf[512];
>  
>  	if (!vma->node.stack) {
> @@ -49,8 +46,8 @@ static void vma_print_allocator(struct i
>  		return;
>  	}
>  
> -	depot_fetch_stack(vma->node.stack, &trace);
> -	snprint_stack_trace(buf, sizeof(buf), &trace, 0);
> +	nr_entries = stack_depot_fetch(vma->node.stack, &entries);
> +	stack_trace_snprint(buf, sizeof(buf), entries, nr_entries, 0);
>  	DRM_DEBUG_DRIVER("vma.node [%08llx + %08llx] %s: inserted at %s\n",
>  			 vma->node.start, vma->node.size, reason, buf);
>  }
> --- a/drivers/gpu/drm/i915/intel_runtime_pm.c
> +++ b/drivers/gpu/drm/i915/intel_runtime_pm.c
> @@ -60,27 +60,20 @@
>  static noinline depot_stack_handle_t __save_depot_stack(void)
>  {
>  	unsigned long entries[STACKDEPTH];
> -	struct stack_trace trace = {
> -		.entries = entries,
> -		.max_entries = ARRAY_SIZE(entries),
> -		.skip = 1,
> -	};
> +	unsigned int n;
>  
> -	save_stack_trace(&trace);
> -	return depot_save_stack(&trace, GFP_NOWAIT | __GFP_NOWARN);
> +	n = stack_trace_save(entries, ARRAY_SIZE(entries), 1);
> +	return stack_depot_save(entries, n, GFP_NOWAIT | __GFP_NOWARN);
>  }
>  
>  static void __print_depot_stack(depot_stack_handle_t stack,
>  				char *buf, int sz, int indent)
>  {
> -	unsigned long entries[STACKDEPTH];
> -	struct stack_trace trace = {
> -		.entries = entries,
> -		.max_entries = ARRAY_SIZE(entries),
> -	};
> +	unsigned long *entries;
> +	unsigned int nr_entries;
>  
> -	depot_fetch_stack(stack, &trace);
> -	snprint_stack_trace(buf, sz, &trace, indent);
> +	nr_entries = stack_depot_fetch(stack, &entries);
> +	stack_trace_snprint(buf, sz, entries, nr_entries, indent);
>  }
>  
>  static void init_intel_runtime_pm_wakeref(struct drm_i915_private *i915)
> 
> 

-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch