[PATCH 5/5] drm/amdgpu: Fix deadlock on runtime suspend

Lukas Wunner
2018-02-11T09:38:28Z

amdgpu's ->runtime_suspend hook calls drm_kms_helper_poll_disable(),
which waits for the output poll worker to finish if it's running.

The output poll worker meanwhile calls pm_runtime_get_sync() in
amdgpu's ->detect hooks, which waits for the ongoing suspend to finish,
causing a deadlock.

Fix by not acquiring a runtime PM ref if the ->detect hooks are called
in the output poll worker's context. This is safe because the poll
worker is only enabled while runtime active and we know that
->runtime_suspend waits for it to finish.

Fixes: d38ceaf99ed0 ("drm/amdgpu: add core driver (v4)")
Cc: stable@vger.kernel.org # v4.2+: 1234567890ab: workqueue: Allow retrieval of current task's work struct
Cc: stable@vger.kernel.org # v4.2+: 1234567890ab: drm: Allow determining if current task is output poll worker
Cc: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Lukas Wunner <lukas@wunner.de>
---
drivers/gpu/drm/amd/amdgpu/amdgpu_connectors.c | 58 +++++++++++++++++---------
1 file changed, 38 insertions(+), 20 deletions(-)

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_connectors.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_connectors.c
index 8ca3783f2deb..74d2efaec52f 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_connectors.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_connectors.c
@@ -736,9 +736,11 @@ amdgpu_connector_lvds_detect(struct drm_connector *connector, bool force)
enum drm_connector_status ret = connector_status_disconnected;
int r;

- r = pm_runtime_get_sync(connector->dev->dev);
- if (r < 0)
- return connector_status_disconnected;
+ if (!drm_kms_helper_is_poll_worker()) {
+ r = pm_runtime_get_sync(connector->dev->dev);
+ if (r < 0)
+ return connector_status_disconnected;
+ }

if (encoder) {
struct amdgpu_encoder *amdgpu_encoder = to_amdgpu_encoder(encoder);
@@ -757,8 +759,12 @@ amdgpu_connector_lvds_detect(struct drm_connector *connector, bool force)
/* check acpi lid status ??? */

amdgpu_connector_update_scratch_regs(connector, ret);
- pm_runtime_mark_last_busy(connector->dev->dev);
- pm_runtime_put_autosuspend(connector->dev->dev);
+
+ if (!drm_kms_helper_is_poll_worker()) {
+ pm_runtime_mark_last_busy(connector->dev->dev);
+ pm_runtime_put_autosuspend(connector->dev->dev);
+ }
+
return ret;
}

@@ -868,9 +874,11 @@ amdgpu_connector_vga_detect(struct drm_connector *connector, bool force)
enum drm_connector_status ret = connector_status_disconnected;
int r;

- r = pm_runtime_get_sync(connector->dev->dev);
- if (r < 0)
- return connector_status_disconnected;
+ if (!drm_kms_helper_is_poll_worker()) {
+ r = pm_runtime_get_sync(connector->dev->dev);
+ if (r < 0)
+ return connector_status_disconnected;
+ }

encoder = amdgpu_connector_best_single_encoder(connector);
if (!encoder)
@@ -924,8 +932,10 @@ amdgpu_connector_vga_detect(struct drm_connector *connector, bool force)
amdgpu_connector_update_scratch_regs(connector, ret);

out:
- pm_runtime_mark_last_busy(connector->dev->dev);
- pm_runtime_put_autosuspend(connector->dev->dev);
+ if (!drm_kms_helper_is_poll_worker()) {
+ pm_runtime_mark_last_busy(connector->dev->dev);
+ pm_runtime_put_autosuspend(connector->dev->dev);
+ }

return ret;
}
@@ -988,9 +998,11 @@ amdgpu_connector_dvi_detect(struct drm_connector *connector, bool force)
enum drm_connector_status ret = connector_status_disconnected;
bool dret = false, broken_edid = false;

- r = pm_runtime_get_sync(connector->dev->dev);
- if (r < 0)
- return connector_status_disconnected;
+ if (!drm_kms_helper_is_poll_worker()) {
+ r = pm_runtime_get_sync(connector->dev->dev);
+ if (r < 0)
+ return connector_status_disconnected;
+ }

if (!force && amdgpu_connector_check_hpd_status_unchanged(connector)) {
ret = connector->status;
@@ -1115,8 +1127,10 @@ amdgpu_connector_dvi_detect(struct drm_connector *connector, bool force)
amdgpu_connector_update_scratch_regs(connector, ret);

exit:
- pm_runtime_mark_last_busy(connector->dev->dev);
- pm_runtime_put_autosuspend(connector->dev->dev);
+ if (!drm_kms_helper_is_poll_worker()) {
+ pm_runtime_mark_last_busy(connector->dev->dev);
+ pm_runtime_put_autosuspend(connector->dev->dev);
+ }

return ret;
}
@@ -1359,9 +1373,11 @@ amdgpu_connector_dp_detect(struct drm_connector *connector, bool force)
struct drm_encoder *encoder = amdgpu_connector_best_single_encoder(connector);
int r;

- r = pm_runtime_get_sync(connector->dev->dev);
- if (r < 0)
- return connector_status_disconnected;
+ if (!drm_kms_helper_is_poll_worker()) {
+ r = pm_runtime_get_sync(connector->dev->dev);
+ if (r < 0)
+ return connector_status_disconnected;
+ }

if (!force && amdgpu_connector_check_hpd_status_unchanged(connector)) {
ret = connector->status;
@@ -1429,8 +1445,10 @@ amdgpu_connector_dp_detect(struct drm_connector *connector, bool force)

amdgpu_connector_update_scratch_regs(connector, ret);
out:
- pm_runtime_mark_last_busy(connector->dev->dev);
- pm_runtime_put_autosuspend(connector->dev->dev);
+ if (!drm_kms_helper_is_poll_worker()) {
+ pm_runtime_mark_last_busy(connector->dev->dev);
+ pm_runtime_put_autosuspend(connector->dev->dev);
+ }

return ret;
}
--
2.15.1