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    Subject[PATCH 4.14 065/140] drm/amdgpu: Fix deadlock on runtime suspend
    Date
    4.14-stable review patch.  If anyone has any objections, please let me know.

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

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