On Fri, Nov 1, 2019 at 2:09 PM Rob Clark <robdclark@xxxxxxxxx> wrote:
>
> From: Rob Clark <robdclark@xxxxxxxxxxxx>
>
> drm_self_refresh_helper_update_avg_times() was incorrectly accessing the
> new incoming state after drm_atomic_helper_commit_hw_done(). But this
> state might have already been superceeded by an !nonblock atomic update
> resulting in dereferencing an already free'd crtc_state.
>
> Fixes: d4da4e33341c ("drm: Measure Self Refresh Entry/Exit times to avoid thrashing")
> Cc: Sean Paul <seanpaul@xxxxxxxxxxxx>
> Signed-off-by: Rob Clark <robdclark@xxxxxxxxxxxx>
> ---
> TODO I *think* this will more or less do the right thing.. althought I'm
> not 100% sure if, for example, we enter psr in a nonblock commit, and
> then leave psr in a !nonblock commit that overtakes the completion of
> the nonblock commit. Not sure if this sort of scenario can happen in
> practice. But not crashing is better than crashing, so I guess we
> should either take this patch or rever the self-refresh helpers until
> Sean can figure out a better solution.
>
> drivers/gpu/drm/drm_atomic_helper.c | 2 ++
> drivers/gpu/drm/drm_self_refresh_helper.c | 11 ++++++-----
> include/drm/drm_atomic.h | 8 ++++++++
> 3 files changed, 16 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/gpu/drm/drm_atomic_helper.c b/drivers/gpu/drm/drm_atomic_helper.c
> index 3ef2ac52ce94..732bd0ce9241 100644
> --- a/drivers/gpu/drm/drm_atomic_helper.c
> +++ b/drivers/gpu/drm/drm_atomic_helper.c
> @@ -2240,6 +2240,8 @@ void drm_atomic_helper_commit_hw_done(struct drm_atomic_state *old_state)
> int i;
>
> for_each_oldnew_crtc_in_state(old_state, crtc, old_crtc_state, new_crtc_state, i) {
> + old_state->crtcs[i].new_self_refresh_active = new_crtc_state->self_refresh_active;
> +
> commit = new_crtc_state->commit;
> if (!commit)
> continue;
> diff --git a/drivers/gpu/drm/drm_self_refresh_helper.c b/drivers/gpu/drm/drm_self_refresh_helper.c
> index 68f4765a5896..77b9079fa578 100644
> --- a/drivers/gpu/drm/drm_self_refresh_helper.c
> +++ b/drivers/gpu/drm/drm_self_refresh_helper.c
> @@ -143,19 +143,20 @@ void drm_self_refresh_helper_update_avg_times(struct drm_atomic_state *state,
> unsigned int commit_time_ms)
> {
> struct drm_crtc *crtc;
> - struct drm_crtc_state *old_crtc_state, *new_crtc_state;
> + struct drm_crtc_state *old_crtc_state;
> int i;
>
> - for_each_oldnew_crtc_in_state(state, crtc, old_crtc_state,
> - new_crtc_state, i) {
> + for_each_old_crtc_in_state(state, crtc, old_crtc_state, i) {
> + bool new_self_refresh_active =
> + state->crtcs[i].new_self_refresh_active;
> struct drm_self_refresh_data *sr_data = crtc->self_refresh_data;
> struct ewma_psr_time *time;
>
> if (old_crtc_state->self_refresh_active ==
> - new_crtc_state->self_refresh_active)
> + new_self_refresh_active)
> continue;
>
> - if (new_crtc_state->self_refresh_active)
> + if (new_self_refresh_active)
> time = &sr_data->entry_avg_ms;
> else
> time = &sr_data->exit_avg_ms;
> diff --git a/include/drm/drm_atomic.h b/include/drm/drm_atomic.h
> index 927e1205d7aa..86baf2b38bb3 100644
> --- a/include/drm/drm_atomic.h
> +++ b/include/drm/drm_atomic.h
> @@ -155,6 +155,14 @@ struct __drm_crtcs_state {
> struct drm_crtc *ptr;
> struct drm_crtc_state *state, *old_state, *new_state;
>
> + /**
> + * @new_self_refresh_active:
> + *
> + * drm_atomic_helper_commit_hw_done() stashes new_crtc_state->self_refresh_active
> + * so that it can be accessed late in drm_self_refresh_helper_update_avg_times().
> + */
> + bool new_self_refresh_active;
> +
Instead of stashing this in crtc, we could generate a bitmask local to
commit_tail and pass that to calc_avg_times? That way we don't have to
worry about someone using this when they shouldn't
Sean
> /**
> * @commit:
> *
> --
> 2.21.0
>
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