Commit b66ea2c2 authored by Chris Wilson's avatar Chris Wilson
Browse files

drm/i915: Use lockdep_pin_lock() over the construction of the request 



During request construction, we take the timeline->mutex to ensure
exclusive access to the ringbuffer (for command emission) and the
timeline itself (for command ordering). The timeline->mutex should not
be dropped by callers until we release it in i915_request_add().

lockdep provides a pin/unpin lock facility to detect accidental unlocks
inside critical sections, so put it to use for request construction.

Signed-off-by: default avatarChris Wilson <chris@chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Reviewed-by: default avatarTvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190403082132.327-1-chris@chris-wilson.co.uk
parent c2400ec3

drivers/gpu/drm/i915/i915_request.c

+5 −0
Original line number Diff line number Diff line
@@ -751,7 +751,10 @@ i915_request_alloc(struct intel_engine_cs *engine, struct i915_gem_context *ctx) 
	rq->infix = rq->ring->emit; /* end of header; start of user payload */



	/* Check that we didn't interrupt ourselves with a new request */

	lockdep_assert_held(&rq->timeline->mutex);

	GEM_BUG_ON(rq->timeline->seqno != rq->fence.seqno);

	rq->cookie = lockdep_pin_lock(&rq->timeline->mutex);



	return rq;



err_unwind:
@@ -1070,6 +1073,8 @@ void i915_request_add(struct i915_request *request) 
		  engine->name, request->fence.context, request->fence.seqno);



	lockdep_assert_held(&request->timeline->mutex);

	lockdep_unpin_lock(&request->timeline->mutex, request->cookie);



	trace_i915_request_add(request);



	/*

drivers/gpu/drm/i915/i915_request.h

+10 −0
Original line number Diff line number Diff line
@@ -26,6 +26,7 @@ 
#define I915_REQUEST_H



#include <linux/dma-fence.h>

#include <linux/lockdep.h>



#include "i915_gem.h"

#include "i915_scheduler.h"
@@ -120,6 +121,15 @@ struct i915_request { 
	 */

	unsigned long rcustate;



	/*

	 * We pin the timeline->mutex while constructing the request to

	 * ensure that no caller accidentally drops it during construction.

	 * The timeline->mutex must be held to ensure that only this caller

	 * can use the ring and manipulate the associated timeline during

	 * construction.

	 */

	struct pin_cookie cookie;



	/*

	 * Fences for the various phases in the request's lifetime.

	 *

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