[PATCH] drm: re-enable error handling

[PATCH] drm: re-enable error handling

[Nicholas Mc Guire]

drm_legacy_ctxbitmap_next() returns idr_alloc() which can return
-ENOMEM, -EINVAL or -ENOSPC none of which are -1 . but the call sites 
of drm_legacy_ctxbitmap_next() seem to be assuming that the error case
would be -1 (original return of drm_ctxbitmap_next() prior to 2.6.23
was actually -1). Thus reenable error handling by checking for < 0.

Signed-off-by: Nicholas Mc Guire <hofrat@osadl.org>
Fixes: 62968144e673 ("drm: convert drm context code to use Linux idr")
---

Problem located with experimental coccinelle script

The noted Fixes tag is one of the commits that removed the -1 return
value in 2.6.23 in drm_ctxbitmap_next() but thats not the only change
that must have taken place to invalidate the error check.

Patch was compile tested with: x86_64_defconfig

Patch is against 4.18-rc4 (localversion-next is next-20180713)

 drivers/gpu/drm/drm_context.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/drm_context.c b/drivers/gpu/drm/drm_context.c
index 3c4000f..f973d28 100644
--- a/drivers/gpu/drm/drm_context.c
+++ b/drivers/gpu/drm/drm_context.c
@@ -372,7 +372,7 @@ int drm_legacy_addctx(struct drm_device *dev, void *data,
 		ctx->handle = drm_legacy_ctxbitmap_next(dev);
 	}
 	DRM_DEBUG("%d\n", ctx->handle);
-	if (ctx->handle == -1) {
+	if (ctx->handle < 0) {
 		DRM_DEBUG("Not enough free contexts.\n");
 		/* Should this return -EBUSY instead? */
 		return -ENOMEM;
-- 
2.1.4

Re: [PATCH] drm: re-enable error handling

[Sean Paul]

On Sat, Jul 14, 2018 at 02:32:12PM +0200, Nicholas Mc Guire wrote:
> drm_legacy_ctxbitmap_next() returns idr_alloc() which can return
> -ENOMEM, -EINVAL or -ENOSPC none of which are -1 . but the call sites 
> of drm_legacy_ctxbitmap_next() seem to be assuming that the error case
> would be -1 (original return of drm_ctxbitmap_next() prior to 2.6.23
> was actually -1). Thus reenable error handling by checking for < 0.
> 
> Signed-off-by: Nicholas Mc Guire <hofrat@osadl.org>

Thanks for your patch, I've applied it to drm-misc-fixes.

Sean

> Fixes: 62968144e673 ("drm: convert drm context code to use Linux idr")
> ---
> 
> Problem located with experimental coccinelle script
> 
> The noted Fixes tag is one of the commits that removed the -1 return
> value in 2.6.23 in drm_ctxbitmap_next() but thats not the only change
> that must have taken place to invalidate the error check.
> 
> Patch was compile tested with: x86_64_defconfig
> 
> Patch is against 4.18-rc4 (localversion-next is next-20180713)
> 
>  drivers/gpu/drm/drm_context.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/drm_context.c b/drivers/gpu/drm/drm_context.c
> index 3c4000f..f973d28 100644
> --- a/drivers/gpu/drm/drm_context.c
> +++ b/drivers/gpu/drm/drm_context.c
> @@ -372,7 +372,7 @@ int drm_legacy_addctx(struct drm_device *dev, void *data,
>  		ctx->handle = drm_legacy_ctxbitmap_next(dev);
>  	}
>  	DRM_DEBUG("%d\n", ctx->handle);
> -	if (ctx->handle == -1) {
> +	if (ctx->handle < 0) {
>  		DRM_DEBUG("Not enough free contexts.\n");
>  		/* Should this return -EBUSY instead? */
>  		return -ENOMEM;
> -- 
> 2.1.4
> 

-- 
Sean Paul, Software Engineer, Google / Chromium OS