Re: [Intel-gfx] [PATCH] drm/i915/selftests: Fix mutex imbalance for igt_render_engine_reset_fallback

[Michel Thierry]

On 23/06/17 06:19, Chris Wilson wrote:

Smatch spots:

drivers/gpu/drm/i915/selftests/intel_hangcheck.c:669 
igt_render_engine_reset_fallback() error: double unlock 
'mutex:&i915->drm.struct_mutex'

Signed-off-by: Chris Wilson <ch...@chris-wilson.co.uk>

Reviewed-by: Michel Thierry <michel.thie...@intel.com>

---
 drivers/gpu/drm/i915/selftests/intel_hangcheck.c | 21 ++++++++++++++-------
 1 file changed, 14 insertions(+), 7 deletions(-)

diff --git a/drivers/gpu/drm/i915/selftests/intel_hangcheck.c 
b/drivers/gpu/drm/i915/selftests/intel_hangcheck.c
index af475189bd52..7096c3911cd3 100644
--- a/drivers/gpu/drm/i915/selftests/intel_hangcheck.c
+++ b/drivers/gpu/drm/i915/selftests/intel_hangcheck.c
@@ -597,12 +597,12 @@ static int igt_render_engine_reset_fallback(void *arg)

        err = hang_init(&h, i915);
        if (err)
-               goto unlock;
+               goto err_unlock;

        rq = hang_create_request(&h, engine, i915->kernel_context);
        if (IS_ERR(rq)) {
                err = PTR_ERR(rq);
-               goto fini;
+               goto err_fini;
        }

        i915_gem_request_get(rq);
@@ -614,7 +614,7 @@ static int igt_render_engine_reset_fallback(void *arg)
        if (!wait_for_hang(&h, rq)) {
                pr_err("Failed to start request %x\n", rq->fence.seqno);
                err = -EIO;
-               goto out_rq;
+               goto err_request;
        }

        reset_engine_count = i915_reset_engine_count(&i915->gpu_error, engine);
@@ -646,13 +646,14 @@ static int igt_render_engine_reset_fallback(void *arg)
         */
        if (i915_terminally_wedged(&i915->gpu_error)) {
                set_bit(I915_RESET_BACKOFF, &i915->gpu_error.flags);
-               mutex_lock(&i915->drm.struct_mutex);
                rq->fence.error = 0;

+               mutex_lock(&i915->drm.struct_mutex);
                set_bit(I915_RESET_HANDOFF, &i915->gpu_error.flags);
                i915_reset(i915);
                GEM_BUG_ON(test_bit(I915_RESET_HANDOFF,
                                    &i915->gpu_error.flags));
+               mutex_unlock(&i915->drm.struct_mutex);

                if (i915_reset_count(&i915->gpu_error) == reset_count) {
                        pr_err("No full GPU reset recorded!\n");
@@ -663,10 +664,8 @@ static int igt_render_engine_reset_fallback(void *arg)

 out_rq:
        i915_gem_request_put(rq);
-fini:
        hang_fini(&h);
-unlock:
-       mutex_unlock(&i915->drm.struct_mutex);
+out_backoff:
        clear_bit(I915_RESET_BACKOFF, &i915->gpu_error.flags);
        wake_up_all(&i915->gpu_error.reset_queue);

@@ -674,6 +673,14 @@ static int igt_render_engine_reset_fallback(void *arg)
                return -EIO;

        return err;
+
+err_request:
+       i915_gem_request_put(rq);
+err_fini:
+       hang_fini(&h);
+err_unlock:
+       mutex_unlock(&i915->drm.struct_mutex);
+       goto out_backoff;
 }

 int intel_hangcheck_live_selftests(struct drm_i915_private *i915)
--
2.13.1

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