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Commit 16c8619a authored by Chris Wilson's avatar Chris Wilson
Browse files

drm/i915: Avoid context dereference inside execlists_submission_tasklet 

A lesson that has to be relearnt over and over again is that the request
does not keep a reference to the context and so we cannot freely
dereference the context from inside the execlists_submission_tasklet. In
particular, we try to do so in the new GEM_TRACE() so convert those over
to the port->context_id we keep for GEM debugging. This means the
tracing now depends on DRM_I915_GEM_DEBUG.

Fixes: bccd3b83 ("drm/i915: Use trace_printk to provide a death rattle for GEM")
References: https://bugs.freedesktop.org/show_bug.cgi?id=104066
References: https://bugs.freedesktop.org/show_bug.cgi?id=104162
References: https://bugs.freedesktop.org/show_bug.cgi?id=104242
References: https://bugs.freedesktop.org/show_bug.cgi?id=104310


Signed-off-by: default avatarChris Wilson <chris@chris-wilson.co.uk>
Cc: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Reviewed-by: default avatarMichel Thierry <michel.thierry@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20171219220916.30882-1-chris@chris-wilson.co.uk
parent 93dff100

drivers/gpu/drm/i915/Kconfig.debug

+1 −1
Original line number Diff line number Diff line
@@ -29,7 +29,6 @@ config DRM_I915_DEBUG 
	select SW_SYNC # signaling validation framework (igt/syncobj*)

	select DRM_I915_SW_FENCE_DEBUG_OBJECTS

	select DRM_I915_SELFTEST

	select DRM_I915_TRACE_GEM

        default n

        help

          Choose this option to turn on extra driver debugging that may affect
@@ -53,6 +52,7 @@ config DRM_I915_DEBUG_GEM 


config DRM_I915_TRACE_GEM

	bool "Insert extra ftrace output from the GEM internals"

	depends on DRM_I915_DEBUG_GEM

	select TRACING

	default n

	help

drivers/gpu/drm/i915/intel_lrc.c

+3 −3
Original line number Diff line number Diff line
@@ -449,7 +449,7 @@ static void execlists_submit_ports(struct intel_engine_cs *engine) 


			GEM_TRACE("%s in[%d]:  ctx=%d.%d, seqno=%x\n",

				  engine->name, n,

				  rq->ctx->hw_id, count,

				  port[n].context_id, count,

				  rq->global_seqno);

		} else {

			GEM_BUG_ON(!n);
@@ -861,7 +861,7 @@ static void execlists_submission_tasklet(unsigned long data) 
			 */



			status = READ_ONCE(buf[2 * head]); /* maybe mmio! */

			GEM_TRACE("%s csb[%dd]: status=0x%08x:0x%08x\n",

			GEM_TRACE("%s csb[%d]: status=0x%08x:0x%08x\n",

				  engine->name, head,

				  status, buf[2*head + 1]);
@@ -905,7 +905,7 @@ static void execlists_submission_tasklet(unsigned long data) 
			rq = port_unpack(port, &count);

			GEM_TRACE("%s out[0]: ctx=%d.%d, seqno=%x\n",

				  engine->name,

				  rq->ctx->hw_id, count,

				  port->context_id, count,

				  rq->global_seqno);

			GEM_BUG_ON(count == 0);

			if (--count == 0) {