On Tue, Jul 17, 2018 at 03:28:21PM +0200, Nicholas Mc Guire wrote:
> drm_legacy_ctxbitmap_next() returns idr_alloc() which can return
> -ENOMEM, -EINVAL or -ENOSPC none of which are -1. since drm_context_t
> is an unsigned int an intermediate variable is used to handle the
> error cases, and then cast to drm_context_t after ensuring that the
> value is >= 0. The explicit cast is to mark the type conversion as
> intentional.
>
> Signed-off-by: Nicholas Mc Guire <hofrat@xxxxxxxxx>
> Reported-by: kbuild test robot <lkp@xxxxxxxxx>
> Fixes: d530b5f1ca0b ("drm: re-enable error handling")
> Fixes: 62968144e673 ("drm: convert drm context code to use Linux idr")
> ---
>
> kbuild test robot reported:
> <snip>
> tree: git://anongit.freedesktop.org/drm/drm-misc for-linux-next-fixes
> head: d530b5f1ca0bb66958a2b714bebe40a1248b9c15
> commit: d530b5f1ca0bb66958a2b714bebe40a1248b9c15 [2/2] drm: re-enable error
> +handling
>
> smatch warnings:
> drivers/gpu/drm/drm_context.c:375 drm_legacy_addctx() warn: unsigned
> +'ctx->handle' is never less than zero.
> <snip>
>
> V2: The proposed fix in d530b5f1ca0b ("drm: re-enable error handling")
> actually was ineffective as the negative return value check was
> against a unsigned int and thus always false as reported by
> kbuild test robot <lkp@xxxxxxxxx>. The below patch removes that
> warning and fixes the original problem of missed error handling.
>
> drm_context_t is actually just used in a few placed so the type could be
> changed but it is also exported via tools/include/uapi/drm/drm.h so
> changing the typedef of drm_context_t could break applications and thus
> this is not an option.
>
> Patch was compile tested with: x86_64_defconfig
>
> Patch is against 4.18-rc4 (localversion-next is next-20180717)
>
> drivers/gpu/drm/drm_context.c | 12 ++++++++----
> 1 file changed, 8 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/gpu/drm/drm_context.c b/drivers/gpu/drm/drm_context.c
> index 3c4000f..78f32a3 100644
> --- a/drivers/gpu/drm/drm_context.c
> +++ b/drivers/gpu/drm/drm_context.c
> @@ -361,22 +361,26 @@ int drm_legacy_addctx(struct drm_device *dev, void *data,
> {
> struct drm_ctx_list *ctx_entry;
> struct drm_ctx *ctx = data;
> + int ret;
>
> if (!drm_core_check_feature(dev, DRIVER_KMS_LEGACY_CONTEXT) &&
> !drm_core_check_feature(dev, DRIVER_LEGACY))
> return -EINVAL;
>
> ctx->handle = drm_legacy_ctxbitmap_next(dev);
Remove this call?
Sean
> - if (ctx->handle == DRM_KERNEL_CONTEXT) {
> + ret = drm_legacy_ctxbitmap_next(dev);
> + if (ret == DRM_KERNEL_CONTEXT) {
> /* Skip kernel's context and get a new one. */
> - ctx->handle = drm_legacy_ctxbitmap_next(dev);
> + ret = drm_legacy_ctxbitmap_next(dev);
> }
> - DRM_DEBUG("%d\n", ctx->handle);
> - if (ctx->handle < 0) {
> + DRM_DEBUG("ctxbitmap is error code %d\n", ret);
> + if (ret < 0) {
> DRM_DEBUG("Not enough free contexts.\n");
> /* Should this return -EBUSY instead? */
> return -ENOMEM;
> }
> + /* valid context is >= 0 */
> + ctx->handle = (drm_context_t)ret;
>
> ctx_entry = kmalloc(sizeof(*ctx_entry), GFP_KERNEL);
> if (!ctx_entry) {
> --
> 2.1.4
>
--
Sean Paul, Software Engineer, Google / Chromium OS
_______________________________________________
dri-devel mailing list
dri-devel@xxxxxxxxxxxxxxxxxxxxx
https://lists.freedesktop.org/mailman/listinfo/dri-devel
