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drm/i915: Enable rcu-only context lookups 

Whilst the contents of the context is still protected by the big
struct_mutex, this is not much of an improvement. It is just one tiny
step towards reducing our BKL.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20170620110547.15947-3-chris@chris-wilson.co.uk
This commit is contained in:
Chris Wilson 2017-06-20 12:05:47 +01:00
parent 5f09a9c8ab
commit 1acfc104cd
4 changed files with 64 additions and 55 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

16
drivers/gpu/drm/i915/i915_drv.h
View File

@ -3533,16 +3533,22 @@ void i915_gem_object_do_bit_17_swizzle(struct drm_i915_gem_object *obj,
void i915_gem_object_save_bit_17_swizzle(struct drm_i915_gem_object *obj,
struct sg_table *pages);
static inline struct i915_gem_context *
__i915_gem_context_lookup_rcu(struct drm_i915_file_private *file_priv, u32 id)
{
return idr_find(&file_priv->context_idr, id);
}
static inline struct i915_gem_context *
i915_gem_context_lookup(struct drm_i915_file_private *file_priv, u32 id)
{
struct i915_gem_context *ctx;
lockdep_assert_held(&file_priv->dev_priv->drm.struct_mutex);
ctx = idr_find(&file_priv->context_idr, id);
if (!ctx)
return ERR_PTR(-ENOENT);
rcu_read_lock();
ctx = __i915_gem_context_lookup_rcu(file_priv, id);
if (ctx && !kref_get_unless_zero(&ctx->ref))
ctx = NULL;
rcu_read_unlock();
return ctx;
}

77
drivers/gpu/drm/i915/i915_gem_context.c
View File

@ -187,7 +187,7 @@ static void i915_gem_context_free(struct i915_gem_context *ctx)
list_del(&ctx->link);
ida_simple_remove(&ctx->i915->contexts.hw_ida, ctx->hw_id);
kfree(ctx);
kfree_rcu(ctx, rcu);
}
static void contexts_free(struct drm_i915_private *i915)
@ -1021,20 +1021,19 @@ int i915_gem_context_destroy_ioctl(struct drm_device *dev, void *data,
if (args->ctx_id == DEFAULT_CONTEXT_HANDLE)
return -ENOENT;
ret = i915_mutex_lock_interruptible(dev);
if (ret)
return ret;
ctx = i915_gem_context_lookup(file_priv, args->ctx_id);
if (IS_ERR(ctx)) {
mutex_unlock(&dev->struct_mutex);
return PTR_ERR(ctx);
}
if (!ctx)
return -ENOENT;
ret = mutex_lock_interruptible(&dev->struct_mutex);
if (ret)
goto out;
__destroy_hw_context(ctx, file_priv);
mutex_unlock(&dev->struct_mutex);
DRM_DEBUG("HW context %d destroyed\n", args->ctx_id);
out:
i915_gem_context_put(ctx);
return 0;
}
@ -1044,17 +1043,11 @@ int i915_gem_context_getparam_ioctl(struct drm_device *dev, void *data,
struct drm_i915_file_private *file_priv = file->driver_priv;
struct drm_i915_gem_context_param *args = data;
struct i915_gem_context *ctx;
int ret;
ret = i915_mutex_lock_interruptible(dev);
if (ret)
return ret;
int ret = 0;
ctx = i915_gem_context_lookup(file_priv, args->ctx_id);
if (IS_ERR(ctx)) {
mutex_unlock(&dev->struct_mutex);
return PTR_ERR(ctx);
}
if (!ctx)
return -ENOENT;
args->size = 0;
switch (args->param) {
@ -1082,8 +1075,8 @@ int i915_gem_context_getparam_ioctl(struct drm_device *dev, void *data,
ret = -EINVAL;
break;
}
mutex_unlock(&dev->struct_mutex);
i915_gem_context_put(ctx);
return ret;
}
@ -1095,15 +1088,13 @@ int i915_gem_context_setparam_ioctl(struct drm_device *dev, void *data,
struct i915_gem_context *ctx;
int ret;
ctx = i915_gem_context_lookup(file_priv, args->ctx_id);
if (!ctx)
return -ENOENT;
ret = i915_mutex_lock_interruptible(dev);
if (ret)
return ret;
ctx = i915_gem_context_lookup(file_priv, args->ctx_id);
if (IS_ERR(ctx)) {
mutex_unlock(&dev->struct_mutex);
return PTR_ERR(ctx);
}
goto out;
switch (args->param) {
case I915_CONTEXT_PARAM_BAN_PERIOD:
@ -1141,6 +1132,8 @@ int i915_gem_context_setparam_ioctl(struct drm_device *dev, void *data,
}
mutex_unlock(&dev->struct_mutex);
out:
i915_gem_context_put(ctx);
return ret;
}
@ -1155,27 +1148,31 @@ int i915_gem_context_reset_stats_ioctl(struct drm_device *dev,
if (args->flags || args->pad)
return -EINVAL;
ret = i915_mutex_lock_interruptible(dev);
if (ret)
return ret;
ret = -ENOENT;
rcu_read_lock();
ctx = __i915_gem_context_lookup_rcu(file->driver_priv, args->ctx_id);
if (!ctx)
goto out;
ctx = i915_gem_context_lookup(file->driver_priv, args->ctx_id);
if (IS_ERR(ctx)) {
mutex_unlock(&dev->struct_mutex);
return PTR_ERR(ctx);
}
/*
* We opt for unserialised reads here. This may result in tearing
* in the extremely unlikely event of a GPU hang on this context
* as we are querying them. If we need that extra layer of protection,
* we should wrap the hangstats with a seqlock.
*/
if (capable(CAP_SYS_ADMIN))
args->reset_count = i915_reset_count(&dev_priv->gpu_error);
else
args->reset_count = 0;
args->batch_active = ctx->guilty_count;
args->batch_pending = ctx->active_count;
args->batch_active = READ_ONCE(ctx->guilty_count);
args->batch_pending = READ_ONCE(ctx->active_count);
mutex_unlock(&dev->struct_mutex);
return 0;
ret = 0;
out:
rcu_read_unlock();
return ret;
}
#if IS_ENABLED(CONFIG_DRM_I915_SELFTEST)

5
drivers/gpu/drm/i915/i915_gem_context.h
View File

@ -99,6 +99,11 @@ struct i915_gem_context {
*/
struct kref ref;
/**
* @rcu: rcu_head for deferred freeing.
*/
struct rcu_head rcu;
/**
* @flags: small set of booleans
*/

21
drivers/gpu/drm/i915/i915_gem_execbuffer.c
View File

@ -669,16 +669,17 @@ static int eb_select_context(struct i915_execbuffer *eb)
struct i915_gem_context *ctx;
ctx = i915_gem_context_lookup(eb->file->driver_priv, eb->args->rsvd1);
if (unlikely(IS_ERR(ctx)))
return PTR_ERR(ctx);
if (unlikely(!ctx))
return -ENOENT;
if (unlikely(i915_gem_context_is_banned(ctx))) {
DRM_DEBUG("Context %u tried to submit while banned\n",
ctx->user_handle);
i915_gem_context_put(ctx);
return -EIO;
}
eb->ctx = i915_gem_context_get(ctx);
eb->ctx = ctx;
eb->vm = ctx->ppgtt ? &ctx->ppgtt->base : &eb->i915->ggtt.base;
eb->context_flags = 0;
@ -2127,7 +2128,6 @@ i915_gem_do_execbuffer(struct drm_device *dev,
if (DBG_FORCE_RELOC || !(args->flags & I915_EXEC_NO_RELOC))
args->flags |= __EXEC_HAS_RELOC;
eb.exec = exec;
eb.ctx = NULL;
eb.invalid_flags = __EXEC_OBJECT_UNKNOWN_FLAGS;
if (USES_FULL_PPGTT(eb.i915))
eb.invalid_flags |= EXEC_OBJECT_NEEDS_GTT;
@ -2182,6 +2182,10 @@ i915_gem_do_execbuffer(struct drm_device *dev,
if (eb_create(&eb))
return -ENOMEM;
err = eb_select_context(&eb);
if (unlikely(err))
goto err_destroy;
/*
* Take a local wakeref for preparing to dispatch the execbuf as
* we expect to access the hardware fairly frequently in the
@ -2190,14 +2194,11 @@ i915_gem_do_execbuffer(struct drm_device *dev,
* 100ms.
*/
intel_runtime_pm_get(eb.i915);
err = i915_mutex_lock_interruptible(dev);
if (err)
goto err_rpm;
err = eb_select_context(&eb);
if (unlikely(err))
goto err_unlock;
err = eb_relocate(&eb);
if (err)
/*
@ -2333,11 +2334,11 @@ err_batch_unpin:
err_vma:
if (eb.exec)
eb_release_vmas(&eb);
i915_gem_context_put(eb.ctx);
err_unlock:
mutex_unlock(&dev->struct_mutex);
err_rpm:
intel_runtime_pm_put(eb.i915);
i915_gem_context_put(eb.ctx);
err_destroy:
eb_destroy(&eb);
if (out_fence_fd != -1)
put_unused_fd(out_fence_fd);