drm/i915: Fix off-by-one in reporting hanging process

ffs() is 1-indexed, but we want to use it as an index into an array, so
use __ffs() instead.

Fixes: 7fe69b86c5d0 ("drm/i915: Remove GPU reset dependence on struct_mutex")
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190315163933.19352-1-chris@chris-wilson.co.uk
(cherry picked from commit 9073e5b26743b8b675cc44a9c0c8f8c3d584e1c0)
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>

diff --git a/drivers/gpu/drm/i915/i915_gpu_error.c b/drivers/gpu/drm/i915/i915_gpu_error.c
index 9a65341fec097e500ace05a410b62f6f19390d21..aa6791255252f1800b2609285fb399653625b000 100644 (file)
--- a/drivers/gpu/drm/i915/i915_gpu_error.c
+++ b/drivers/gpu/drm/i915/i915_gpu_error.c
@@ -1721,7 +1721,7 @@ error_msg(struct i915_gpu_state *error, unsigned long engines, const char *msg)
                        i915_error_generate_code(error, engines));
        if (engines) {
                /* Just show the first executing process, more is confusing */
-               i = ffs(engines);
+               i = __ffs(engines);
                len += scnprintf(error->error_msg + len,
                                 sizeof(error->error_msg) - len,
                                 ", in %s [%d]",