Re: [Intel-gfx] [PATCH 4/5] drm/atomic: Fix freeing connector/plane state too early by tracking commits, v2.

Maarten Lankhorst
2017-08-30T12:46:35Z

Op 30-08-17 om 14:40 schreef Daniel Vetter:
> On Wed, Aug 30, 2017 at 02:17:51PM +0200, Maarten Lankhorst wrote:
>> Currently we neatly track the crtc state, but forget to look at
>> plane/connector state.
>>
>> When doing a nonblocking modeset, immediately followed by a setprop
>> before the modeset completes, the setprop will see the modesets new
>> state as the old state and free it.
>>
>> This has to be solved by waiting for hw_done on the connector, even
>> if it's not assigned to a crtc. When a connector is unbound we take
>> the last crtc commit, and when it stays unbound we create a new
>> fake crtc commit for that gets signaled on hw_done for all the
>> planes/connectors.
>>
>> We wait for it the same way as we do for crtc's, which will make
>> sure we never run into a use-after-free situation.
>>
>> Changes since v1:
>> - Only create a single disable commit. (danvet)
>> - Fix leak in intel_legacy_cursor_update.
>>
>> Signed-off-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
>> Testcase: kms_atomic_transition.plane-use-after-nonblocking-unbind*
>> Cc: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
>> ---
>> drivers/gpu/drm/drm_atomic.c | 4 +
>> drivers/gpu/drm/drm_atomic_helper.c | 156 +++++++++++++++++++++++++++++++++--
>> drivers/gpu/drm/i915/intel_display.c | 2 +
>> include/drm/drm_atomic.h | 12 +++
>> include/drm/drm_connector.h | 7 ++
>> include/drm/drm_plane.h | 7 ++
>> 6 files changed, 182 insertions(+), 6 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/drm_atomic.c b/drivers/gpu/drm/drm_atomic.c
>> index 2cce48f203e0..75f5f74de9bf 100644
>> --- a/drivers/gpu/drm/drm_atomic.c
>> +++ b/drivers/gpu/drm/drm_atomic.c
>> @@ -192,6 +192,10 @@ void drm_atomic_state_default_clear(struct drm_atomic_state *state)
>> }
>> state->num_private_objs = 0;
>>
>> + if (state->fake_commit) {
>> + drm_crtc_commit_put(state->fake_commit);
>> + state->fake_commit = NULL;
>> + }
>> }
>> EXPORT_SYMBOL(drm_atomic_state_default_clear);
>>
>> diff --git a/drivers/gpu/drm/drm_atomic_helper.c b/drivers/gpu/drm/drm_atomic_helper.c
>> index 8ccb8b6536c0..034f563fb130 100644
>> --- a/drivers/gpu/drm/drm_atomic_helper.c
>> +++ b/drivers/gpu/drm/drm_atomic_helper.c
>> @@ -1644,6 +1644,40 @@ static void release_crtc_commit(struct completion *completion)
>> drm_crtc_commit_put(commit);
>> }
>>
>> +static void init_commit(struct drm_crtc_commit *commit, struct drm_crtc *crtc)
>> +{
>> + init_completion(&commit->flip_done);
>> + init_completion(&commit->hw_done);
>> + init_completion(&commit->cleanup_done);
>> + INIT_LIST_HEAD(&commit->commit_entry);
>> + kref_init(&commit->ref);
>> + commit->crtc = crtc;
>> +}
>> +
>> +static struct drm_crtc_commit *
>> +fake_or_crtc_commit(struct drm_atomic_state *state, struct drm_crtc *crtc)
>> +{
>> + struct drm_crtc_commit *commit;
>> +
>> + if (crtc) {
>> + struct drm_crtc_state *new_crtc_state;
>> +
>> + new_crtc_state = drm_atomic_get_new_crtc_state(state, crtc);
>> +
>> + commit = new_crtc_state->commit;
>> + } else if (!state->fake_commit) {
>> + state->fake_commit = commit = kzalloc(sizeof(*commit), GFP_KERNEL);
>> + if (!commit)
>> + return NULL;
>> +
>> + init_commit(commit, NULL);
>> + } else
>> + commit = state->fake_commit;
>> +
>> + drm_crtc_commit_get(commit);
> Double refcount for the case where you call init_commit? Aka I think this
> leaks.
>
>> + return commit;
>> +}
>> +
>> /**
>> * drm_atomic_helper_setup_commit - setup possibly nonblocking commit
>> * @state: new modeset state to be committed
>> @@ -1692,6 +1726,10 @@ int drm_atomic_helper_setup_commit(struct drm_atomic_state *state,
>> {
>> struct drm_crtc *crtc;
>> struct drm_crtc_state *old_crtc_state, *new_crtc_state;
>> + struct drm_connector *conn;
>> + struct drm_connector_state *old_conn_state, *new_conn_state;
>> + struct drm_plane *plane;
>> + struct drm_plane_state *old_plane_state, *new_plane_state;
>> struct drm_crtc_commit *commit;
>> int i, ret;
>>
>> @@ -1700,12 +1738,7 @@ int drm_atomic_helper_setup_commit(struct drm_atomic_state *state,
>> if (!commit)
>> return -ENOMEM;
>>
>> - init_completion(&commit->flip_done);
>> - init_completion(&commit->hw_done);
>> - init_completion(&commit->cleanup_done);
>> - INIT_LIST_HEAD(&commit->commit_entry);
>> - kref_init(&commit->ref);
>> - commit->crtc = crtc;
>> + init_commit(commit, crtc);
>>
>> new_crtc_state->commit = commit;
>>
>> @@ -1741,6 +1774,36 @@ int drm_atomic_helper_setup_commit(struct drm_atomic_state *state,
>> drm_crtc_commit_get(commit);
>> }
>>
>> + for_each_oldnew_connector_in_state(state, conn, old_conn_state, new_conn_state, i) {
> Maybe a commen there like
> /* commit tracked through the crtc_state->commit */
> Feels at least a bit non-obvious how this works.
>
>> + if (new_conn_state->crtc)
>> + continue;
>> +
> Please add the
>
> /* Userspace is not allowed to get ahead of the previous
> * commit with nonblocking ones. */
>
> comment from stall_checks here and below. Even better if we could extract
> this, but macro is ugly and functions wont work.
Ok.
>> + if (nonblock && old_conn_state->commit &&
>> + !try_wait_for_completion(&old_conn_state->commit->flip_done))
>> + return -EBUSY;
>> +
>> + commit = fake_or_crtc_commit(state, old_conn_state->crtc);
>> + if (!commit)
>> + return -ENOMEM;
>> +
>> + new_conn_state->commit = commit;
>> + }
>> +
>> + for_each_oldnew_plane_in_state(state, plane, old_plane_state, new_plane_state, i) {
>> + if (new_plane_state->crtc)
>> + continue;
>> +
>> + if (nonblock && old_plane_state->commit &&
>> + !try_wait_for_completion(&old_plane_state->commit->flip_done))
>> + return -EBUSY;
>> +
>> + commit = fake_or_crtc_commit(state, old_plane_state->crtc);
>> + if (!commit)
>> + return -ENOMEM;
>> +
>> + new_plane_state->commit = commit;
>> + }
>> +
>> return 0;
>> }
>> EXPORT_SYMBOL(drm_atomic_helper_setup_commit);
>> @@ -1761,6 +1824,10 @@ void drm_atomic_helper_wait_for_dependencies(struct drm_atomic_state *old_state)
>> {
>> struct drm_crtc *crtc;
>> struct drm_crtc_state *old_crtc_state;
>> + struct drm_plane *plane;
>> + struct drm_plane_state *old_plane_state;
>> + struct drm_connector *conn;
>> + struct drm_connector_state *old_conn_state;
>> struct drm_crtc_commit *commit;
>> int i;
>> long ret;
>> @@ -1785,6 +1852,48 @@ void drm_atomic_helper_wait_for_dependencies(struct drm_atomic_state *old_state)
>> DRM_ERROR("[CRTC:%d:%s] flip_done timed out\n",
>> crtc->base.id, crtc->name);
>> }
>> +
>> + for_each_old_connector_in_state(old_state, conn, old_conn_state, i) {
>> + commit = old_conn_state->commit;
>> +
>> + if (!commit)
>> + continue;
>> +
>> + ret = wait_for_completion_timeout(&commit->hw_done,
>> + 10*HZ);
>> + if (ret == 0)
>> + DRM_ERROR("[CONNECTOR:%d:%s] hw_done timed out\n",
>> + conn->base.id, conn->name);
>> +
>> + /* Currently no support for overwriting flips, hence
>> + * stall for previous one to execute completely. */
>> + ret = wait_for_completion_timeout(&commit->flip_done,
>> + 10*HZ);
>> + if (ret == 0)
>> + DRM_ERROR("[CONNECTOR:%d:%s] flip_done timed out\n",
>> + conn->base.id, conn->name);
>> + }
>> +
>> + for_each_old_plane_in_state(old_state, plane, old_plane_state, i) {
>> + commit = old_plane_state->commit;
>> +
>> + if (!commit)
>> + continue;
>> +
>> + ret = wait_for_completion_timeout(&commit->hw_done,
>> + 10*HZ);
>> + if (ret == 0)
>> + DRM_ERROR("[PLANE:%d:%s] hw_done timed out\n",
>> + plane->base.id, plane->name);
>> +
>> + /* Currently no support for overwriting flips, hence
>> + * stall for previous one to execute completely. */
>> + ret = wait_for_completion_timeout(&commit->flip_done,
>> + 10*HZ);
>> + if (ret == 0)
>> + DRM_ERROR("[PLANE:%d:%s] flip_done timed out\n",
>> + plane->base.id, plane->name);
>> + }
>> }
>> EXPORT_SYMBOL(drm_atomic_helper_wait_for_dependencies);
>>
>> @@ -1819,6 +1928,11 @@ void drm_atomic_helper_commit_hw_done(struct drm_atomic_state *old_state)
>> WARN_ON(new_crtc_state->event);
>> complete_all(&commit->hw_done);
>> }
>> +
>> + if (old_state->fake_commit) {
>> + complete_all(&old_state->fake_commit->hw_done);
>> + complete_all(&old_state->fake_commit->flip_done);
>> + }
> Just to avoid surprises, I think we should also complete_all(cleanup_done)
> on the fake commit in cleanup_done().
Sure, now there's only 1 it makes sense. :)
>> }
>> EXPORT_SYMBOL(drm_atomic_helper_commit_hw_done);
>>
>> @@ -2241,6 +2355,28 @@ int drm_atomic_helper_swap_state(struct drm_atomic_state *state,
>> if (ret)
>> return ret;
>> }
>> +
>> + for_each_old_connector_in_state(state, connector, old_conn_state, i) {
>> + commit = old_conn_state->commit;
>> +
>> + if (!commit)
>> + continue;
>> +
>> + ret = wait_for_completion_interruptible(&commit->hw_done);
>> + if (ret)
>> + return ret;
>> + }
>> +
>> + for_each_old_plane_in_state(state, plane, old_plane_state, i) {
>> + commit = old_plane_state->commit;
>> +
>> + if (!commit)
>> + continue;
>> +
>> + ret = wait_for_completion_interruptible(&commit->hw_done);
>> + if (ret)
>> + return ret;
>> + }
>> }
>>
>> for_each_oldnew_connector_in_state(state, connector, old_conn_state, new_conn_state, i) {
>> @@ -3223,6 +3359,7 @@ void __drm_atomic_helper_plane_duplicate_state(struct drm_plane *plane,
>> drm_framebuffer_get(state->fb);
>>
>> state->fence = NULL;
>> + state->commit = NULL;
>> }
>> EXPORT_SYMBOL(__drm_atomic_helper_plane_duplicate_state);
>>
>> @@ -3264,6 +3401,9 @@ void __drm_atomic_helper_plane_destroy_state(struct drm_plane_state *state)
>>
>> if (state->fence)
>> dma_fence_put(state->fence);
>> +
>> + if (state->commit)
>> + drm_crtc_commit_put(state->commit);
>> }
>> EXPORT_SYMBOL(__drm_atomic_helper_plane_destroy_state);
>>
>> @@ -3342,6 +3482,7 @@ __drm_atomic_helper_connector_duplicate_state(struct drm_connector *connector,
>> memcpy(state, connector->state, sizeof(*state));
>> if (state->crtc)
>> drm_connector_get(connector);
>> + state->commit = NULL;
>> }
>> EXPORT_SYMBOL(__drm_atomic_helper_connector_duplicate_state);
>>
>> @@ -3468,6 +3609,9 @@ __drm_atomic_helper_connector_destroy_state(struct drm_connector_state *state)
>> {
>> if (state->crtc)
>> drm_connector_put(state->connector);
>> +
>> + if (state->commit)
>> + drm_crtc_commit_put(state->commit);
>> }
>> EXPORT_SYMBOL(__drm_atomic_helper_connector_destroy_state);
>>
>> diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
>> index 3f3cb96aa11e..70ce02753177 100644
>> --- a/drivers/gpu/drm/i915/intel_display.c
>> +++ b/drivers/gpu/drm/i915/intel_display.c
>> @@ -13109,8 +13109,10 @@ intel_legacy_cursor_update(struct drm_plane *plane,
>>
>> /* Swap plane state */
>> new_plane_state->fence = old_plane_state->fence;
>> + new_plane_state->commit = old_plane_state->commit;
>> *to_intel_plane_state(old_plane_state) = *to_intel_plane_state(new_plane_state);
>> new_plane_state->fence = NULL;
>> + new_plane_state->commit = NULL;
> Would be good if we could switch to Gustavo's async work and push these
> tricks into shared code ...
We do this as an evil hack because we can't track whether something is using the current plane or not.

If we apply patch 5, we could directly swap plane->state because we know whether the cursor plane is in use or not,
and get rid of this evil hack here.
>
>> new_plane_state->fb = old_fb;
>> to_intel_plane_state(new_plane_state)->vma = NULL;
>>
>> diff --git a/include/drm/drm_atomic.h b/include/drm/drm_atomic.h
>> index e76d9f95c191..ba976f4a4938 100644
>> --- a/include/drm/drm_atomic.h
>> +++ b/include/drm/drm_atomic.h
>> @@ -236,6 +236,18 @@ struct drm_atomic_state {
>> struct drm_modeset_acquire_ctx *acquire_ctx;
>>
>> /**
>> + * @fake_commit:
>> + *
>> + * Used for signaling unbound planes/connectors.
>> + * When a connector or plane is not bound to any CRTC, it's still important
>> + * to preserve linearity to prevent the atomic states from being freed to early.
> s/to early/too early/.
>
>> + *
>> + * This commit (if set) is not bound to any crtc, but will be completed when
>> + * drm_atomic_helper_commit_hw_done() is called.
> ... and drm_atomic_helper_cleanup_done() ...
>
>
>> + */
>> + struct drm_crtc_commit *fake_commit;
>> +
>> + /**
>> * @commit_work:
>> *
>> * Work item which can be used by the driver or helpers to execute the
>> diff --git a/include/drm/drm_connector.h b/include/drm/drm_connector.h
>> index ea8da401c93c..8837649d16e8 100644
>> --- a/include/drm/drm_connector.h
>> +++ b/include/drm/drm_connector.h
>> @@ -347,6 +347,13 @@ struct drm_connector_state {
>>
>> struct drm_atomic_state *state;
>>
>> + /**
>> + * @commit: Tracks the pending commit to prevent use-after-free conditions.
>> + *
>> + * Is only set when @crtc is NULL.
>> + */
>> + struct drm_crtc_commit *commit;
>> +
>> struct drm_tv_connector_state tv;
>>
>> /**
>> diff --git a/include/drm/drm_plane.h b/include/drm/drm_plane.h
>> index 73f90f9d057f..7d96116fd4c4 100644
>> --- a/include/drm/drm_plane.h
>> +++ b/include/drm/drm_plane.h
>> @@ -123,6 +123,13 @@ struct drm_plane_state {
>> */
>> bool visible;
>>
>> + /**
>> + * @commit: Tracks the pending commit to prevent use-after-free conditions.
>> + *
>> + * Is only set when @crtc is NULL.
>> + */
>> + struct drm_crtc_commit *commit;
>> +
>> struct drm_atomic_state *state;
>> };
> With the above nits addressed:
>
> Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
+1