From cfe7288c276e359eebf057699fe86c2f8af14224 Mon Sep 17 00:00:00 2001 From: Chris Wilson Date: Mon, 15 Jul 2019 09:09:28 +0100 Subject: [PATCH] drm/i915: Lock the engine while dumping the active request We cannot let the request be retired and freed while we are trying to dump it during error capture. It is not sufficient just to grab a reference to the request, as during retirement we may free the ring which we are also dumping. So take the engine lock to prevent retiring and freeing of the request. Reported-by: Alex Shumsky Fixes: 83c317832eb1 ("drm/i915: Dump the ringbuffer of the active request for debugging") Signed-off-by: Chris Wilson Cc: Tvrtko Ursulin Cc: Joonas Lahtinen Cc: Alex Shumsky Reviewed-by: Tvrtko Ursulin Link: https://patchwork.freedesktop.org/patch/msgid/20190715080946.15593-6-chris@chris-wilson.co.uk --- drivers/gpu/drm/i915/gt/intel_engine_cs.c | 11 ++++------- drivers/gpu/drm/i915/i915_gpu_error.c | 6 ++++-- 2 files changed, 8 insertions(+), 9 deletions(-) diff --git a/drivers/gpu/drm/i915/gt/intel_engine_cs.c b/drivers/gpu/drm/i915/gt/intel_engine_cs.c index 022e00eb79ad..9570659aa360 100644 --- a/drivers/gpu/drm/i915/gt/intel_engine_cs.c +++ b/drivers/gpu/drm/i915/gt/intel_engine_cs.c @@ -1471,6 +1471,7 @@ void intel_engine_dump(struct intel_engine_cs *engine, struct i915_gpu_error * const error = &engine->i915->gpu_error; struct i915_request *rq; intel_wakeref_t wakeref; + unsigned long flags; if (header) { va_list ap; @@ -1490,10 +1491,9 @@ void intel_engine_dump(struct intel_engine_cs *engine, i915_reset_engine_count(error, engine), i915_reset_count(error)); - rcu_read_lock(); - drm_printf(m, "\tRequests:\n"); + spin_lock_irqsave(&engine->active.lock, flags); rq = intel_engine_find_active_request(engine); if (rq) { print_request(m, rq, "\t\tactive "); @@ -1513,8 +1513,7 @@ void intel_engine_dump(struct intel_engine_cs *engine, print_request_ring(m, rq); } - - rcu_read_unlock(); + spin_unlock_irqrestore(&engine->active.lock, flags); wakeref = intel_runtime_pm_get_if_in_use(&engine->i915->runtime_pm); if (wakeref) { @@ -1676,7 +1675,6 @@ struct i915_request * intel_engine_find_active_request(struct intel_engine_cs *engine) { struct i915_request *request, *active = NULL; - unsigned long flags; /* * We are called by the error capture, reset and to dump engine @@ -1689,7 +1687,7 @@ intel_engine_find_active_request(struct intel_engine_cs *engine) * At all other times, we must assume the GPU is still running, but * we only care about the snapshot of this moment. */ - spin_lock_irqsave(&engine->active.lock, flags); + lockdep_assert_held(&engine->active.lock); list_for_each_entry(request, &engine->active.requests, sched.link) { if (i915_request_completed(request)) continue; @@ -1704,7 +1702,6 @@ intel_engine_find_active_request(struct intel_engine_cs *engine) active = request; break; } - spin_unlock_irqrestore(&engine->active.lock, flags); return active; } diff --git a/drivers/gpu/drm/i915/i915_gpu_error.c b/drivers/gpu/drm/i915/i915_gpu_error.c index 78e388fa059c..c5b89bf4d616 100644 --- a/drivers/gpu/drm/i915/i915_gpu_error.c +++ b/drivers/gpu/drm/i915/i915_gpu_error.c @@ -1411,6 +1411,7 @@ static void gem_record_rings(struct i915_gpu_state *error) struct intel_engine_cs *engine = i915->engine[i]; struct drm_i915_error_engine *ee = &error->engine[i]; struct i915_request *request; + unsigned long flags; ee->engine_id = -1; @@ -1422,10 +1423,11 @@ static void gem_record_rings(struct i915_gpu_state *error) error_record_engine_registers(error, engine, ee); error_record_engine_execlists(engine, ee); + spin_lock_irqsave(&engine->active.lock, flags); request = intel_engine_find_active_request(engine); if (request) { struct i915_gem_context *ctx = request->gem_context; - struct intel_ring *ring; + struct intel_ring *ring = request->ring; ee->vm = ctx->vm ?: &engine->gt->ggtt->vm; @@ -1455,7 +1457,6 @@ static void gem_record_rings(struct i915_gpu_state *error) ee->rq_post = request->postfix; ee->rq_tail = request->tail; - ring = request->ring; ee->cpu_ring_head = ring->head; ee->cpu_ring_tail = ring->tail; ee->ringbuffer = @@ -1463,6 +1464,7 @@ static void gem_record_rings(struct i915_gpu_state *error) engine_record_requests(engine, request, ee); } + spin_unlock_irqrestore(&engine->active.lock, flags); ee->hws_page = i915_error_object_create(i915, -- 2.39.5