Commit 2d60d3e0 authored by Chris Wilson's avatar Chris Wilson
Browse files

drm/i915/gem: Reduce ctx->engines_mutex for get_engines() 



Take a snapshot of the ctx->engines, so we can avoid taking the
ctx->engines_mutex for a mere read in get_engines().

Signed-off-by: default avatarChris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: default avatarAndi Shyti <andi.shyti@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210114135612.13210-4-chris@chris-wilson.co.uk
parent 1a72e741

drivers/gpu/drm/i915/gem/i915_gem_context.c

+8 −31
Original line number Diff line number Diff line
@@ -1843,27 +1843,6 @@ set_engines(struct i915_gem_context *ctx, 
	return 0;

}



static struct i915_gem_engines *

__copy_engines(struct i915_gem_engines *e)

{

	struct i915_gem_engines *copy;

	unsigned int n;



	copy = alloc_engines(e->num_engines);

	if (!copy)

		return ERR_PTR(-ENOMEM);



	for (n = 0; n < e->num_engines; n++) {

		if (e->engines[n])

			copy->engines[n] = intel_context_get(e->engines[n]);

		else

			copy->engines[n] = NULL;

	}

	copy->num_engines = n;



	return copy;

}



static int

get_engines(struct i915_gem_context *ctx,

	    struct drm_i915_gem_context_param *args)
@@ -1871,19 +1850,17 @@ get_engines(struct i915_gem_context *ctx, 
	struct i915_context_param_engines __user *user;

	struct i915_gem_engines *e;

	size_t n, count, size;

	bool user_engines;

	int err = 0;



	err = mutex_lock_interruptible(&ctx->engines_mutex);

	if (err)

		return err;

	e = __context_engines_await(ctx, &user_engines);

	if (!e)

		return -ENOENT;



	e = NULL;

	if (i915_gem_context_user_engines(ctx))

		e = __copy_engines(i915_gem_context_engines(ctx));

	mutex_unlock(&ctx->engines_mutex);

	if (IS_ERR_OR_NULL(e)) {

	if (!user_engines) {

		i915_sw_fence_complete(&e->fence);

		args->size = 0;

		return PTR_ERR_OR_ZERO(e);

		return 0;

	}



	count = e->num_engines;
@@ -1934,7 +1911,7 @@ get_engines(struct i915_gem_context *ctx, 
	args->size = size;



err_free:

	free_engines(e);

	i915_sw_fence_complete(&e->fence);

	return err;

}