[Intel-gfx] [bug report] drm/i915/guc: Implement multi-lrc submission

[Dan Carpenter <dan.carpenter@oracle.com>]

Hello Matthew Brost,

The patch 6b540bf6f143: "drm/i915/guc: Implement multi-lrc
submission" from Oct 14, 2021, leads to the following Smatch static
checker warning:

	drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c:752 __guc_add_request()
	warn: refcount leak 'ce->ref.refcount.refs.counter': lines='752'

drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c
    672 static int __guc_add_request(struct intel_guc *guc, struct i915_request *rq)
    673 {
    674         int err = 0;
    675         struct intel_context *ce = request_to_scheduling_context(rq);
    676         u32 action[3];
    677         int len = 0;
    678         u32 g2h_len_dw = 0;
    679         bool enabled;
    680 
    681         lockdep_assert_held(&rq->engine->sched_engine->lock);
    682 
    683         /*
    684          * Corner case where requests were sitting in the priority list or a
    685          * request resubmitted after the context was banned.
    686          */
    687         if (unlikely(intel_context_is_banned(ce))) {
    688                 i915_request_put(i915_request_mark_eio(rq));
    689                 intel_engine_signal_breadcrumbs(ce->engine);
    690                 return 0;
    691         }
    692 
    693         GEM_BUG_ON(!atomic_read(&ce->guc_id.ref));
    694         GEM_BUG_ON(context_guc_id_invalid(ce));
    695 
    696         if (context_policy_required(ce)) {
    697                 err = guc_context_policy_init_v70(ce, false);
    698                 if (err)
    699                         return err;
    700         }
    701 
    702         spin_lock(&ce->guc_state.lock);
    703 
    704         /*
    705          * The request / context will be run on the hardware when scheduling
    706          * gets enabled in the unblock. For multi-lrc we still submit the
    707          * context to move the LRC tails.
    708          */
    709         if (unlikely(context_blocked(ce) && !intel_context_is_parent(ce)))
    710                 goto out;
    711 
    712         enabled = context_enabled(ce) || context_blocked(ce);
    713 
    714         if (!enabled) {
    715                 action[len++] = INTEL_GUC_ACTION_SCHED_CONTEXT_MODE_SET;
    716                 action[len++] = ce->guc_id.id;
    717                 action[len++] = GUC_CONTEXT_ENABLE;
    718                 set_context_pending_enable(ce);
    719                 intel_context_get(ce);
    720                 g2h_len_dw = G2H_LEN_DW_SCHED_CONTEXT_MODE_SET;
    721         } else {
    722                 action[len++] = INTEL_GUC_ACTION_SCHED_CONTEXT;
    723                 action[len++] = ce->guc_id.id;
    724         }
    725 
    726         err = intel_guc_send_nb(guc, action, len, g2h_len_dw);
    727         if (!enabled && !err) {
    728                 trace_intel_context_sched_enable(ce);
    729                 atomic_inc(&guc->outstanding_submission_g2h);
    730                 set_context_enabled(ce);
    731 
    732                 /*
    733                  * Without multi-lrc KMD does the submission step (moving the
    734                  * lrc tail) so enabling scheduling is sufficient to submit the
    735                  * context. This isn't the case in multi-lrc submission as the
    736                  * GuC needs to move the tails, hence the need for another H2G
    737                  * to submit a multi-lrc context after enabling scheduling.
    738                  */
    739                 if (intel_context_is_parent(ce)) {
    740                         action[0] = INTEL_GUC_ACTION_SCHED_CONTEXT;
    741                         err = intel_guc_send_nb(guc, action, len - 1, 0);

Should this have a something like:

				if (err)
					intel_context_put(ce);

    742                 }
    743         } else if (!enabled) {
    744                 clr_context_pending_enable(ce);
    745                 intel_context_put(ce);
    746         }
    747         if (likely(!err))
    748                 trace_i915_request_guc_submit(rq);
    749 
    750 out:
    751         spin_unlock(&ce->guc_state.lock);
--> 752         return err;
    753 }

regards,
dan carpenter