4.14-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Lukas Wunner <lu...@wunner.de>

commit aa0aad57909eb321746325951d66af88a83bc956 upstream.

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: sta...@vger.kernel.org # v4.2+: 27d4ee03078a: workqueue: Allow retrieval of 
current task's work struct
Cc: sta...@vger.kernel.org # v4.2+: 25c058ccaf2e: drm: Allow determining if 
current task is output poll worker
Cc: Alex Deucher <alexander.deuc...@amd.com>
Tested-by: Mike Lothian <m...@fireburn.co.uk>
Reviewed-by: Lyude Paul <ly...@redhat.com>
Signed-off-by: Lukas Wunner <lu...@wunner.de>
Link: 
https://patchwork.freedesktop.org/patch/msgid/4c9bf72aacae1eef062bd134cd112e0770a7f121.1518338789.git.lu...@wunner.de
Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org>

---
 drivers/gpu/drm/amd/amdgpu/amdgpu_connectors.c |   58 ++++++++++++++++---------
 1 file changed, 38 insertions(+), 20 deletions(-)

--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_connectors.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_connectors.c
@@ -739,9 +739,11 @@ amdgpu_connector_lvds_detect(struct drm_
        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);
@@ -760,8 +762,12 @@ amdgpu_connector_lvds_detect(struct drm_
        /* 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;
 }
 
@@ -871,9 +877,11 @@ amdgpu_connector_vga_detect(struct drm_c
        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)
@@ -927,8 +935,10 @@ amdgpu_connector_vga_detect(struct drm_c
        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;
 }
@@ -991,9 +1001,11 @@ amdgpu_connector_dvi_detect(struct drm_c
        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;
@@ -1118,8 +1130,10 @@ out:
        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;
 }
@@ -1362,9 +1376,11 @@ amdgpu_connector_dp_detect(struct drm_co
        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;
@@ -1432,8 +1448,10 @@ amdgpu_connector_dp_detect(struct drm_co
 
        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;
 }


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