Commit a16a4052 authored by Chris Wilson's avatar Chris Wilson

drm/i915: Track the previous pinned context inside the request

As the contexts are accessed by the hardware until the switch is completed
to a new context, the hardware may still be writing to the context object
after the breadcrumb is visible. We must not unpin/unbind/prune that
object whilst still active and so we keep the previous context pinned until
the following request. We can generalise the tracking we already do via
the engine->last_context and move it to the request so that it works
equally for execlists and GuC.

v2: Drop the execlists double pin as that exposes a race inside the lrc
irq handler as it tries to access the context after it may be retired.
Signed-off-by: default avatarChris Wilson <chris@chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>
Reviewed-by: default avatarJoonas Lahtinen <joonas.lahtinen@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1461833819-3991-22-git-send-email-chris@chris-wilson.co.uk
parent 73db04cf
......@@ -2305,6 +2305,17 @@ struct drm_i915_gem_request {
struct intel_context *ctx;
struct intel_ringbuffer *ringbuf;
/**
* Context related to the previous request.
* As the contexts are accessed by the hardware until the switch is
* completed to a new context, the hardware may still be writing
* to the context object after the breadcrumb is visible. We must
* not unpin/unbind/prune that object whilst still active and so
* we keep the previous context pinned until the following (this)
* request is retired.
*/
struct intel_context *previous_context;
/** Batch buffer related to this request if any (used for
error state dump only) */
struct drm_i915_gem_object *batch_obj;
......
......@@ -1413,13 +1413,13 @@ static void i915_gem_request_retire(struct drm_i915_gem_request *request)
list_del_init(&request->list);
i915_gem_request_remove_from_client(request);
if (request->ctx) {
if (request->previous_context) {
if (i915.enable_execlists)
intel_lr_context_unpin(request->ctx, request->engine);
i915_gem_context_unreference(request->ctx);
intel_lr_context_unpin(request->previous_context,
request->engine);
}
i915_gem_context_unreference(request->ctx);
i915_gem_request_unreference(request);
}
......
......@@ -771,12 +771,14 @@ intel_logical_ring_advance_and_submit(struct drm_i915_gem_request *request)
if (intel_engine_stopped(engine))
return 0;
if (engine->last_context != request->ctx) {
if (engine->last_context)
intel_lr_context_unpin(engine->last_context, engine);
intel_lr_context_pin(request->ctx, engine);
/* We keep the previous context alive until we retire the following
* request. This ensures that any the context object is still pinned
* for any residual writes the HW makes into it on the context switch
* into the next object following the breadcrumb. Otherwise, we may
* retire the context too early.
*/
request->previous_context = engine->last_context;
engine->last_context = request->ctx;
}
if (dev_priv->guc.execbuf_client)
i915_guc_submit(dev_priv->guc.execbuf_client, request);
......
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