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    Subject[PATCH 4.19 082/287] drm/msm/mdp5: Fix global state lock backoff
    Date
    From: Rob Clark <robdclark@chromium.org>

    [ Upstream commit 92ef86ab513593c6329d04146e61f9a670e72fc5 ]

    We need to grab the lock after the early return for !hwpipe case.
    Otherwise, we could have hit contention yet still returned 0.

    Fixes an issue that the new CONFIG_DRM_DEBUG_MODESET_LOCK stuff flagged
    in CI:

    WARNING: CPU: 0 PID: 282 at drivers/gpu/drm/drm_modeset_lock.c:296 drm_modeset_lock+0xf8/0x154
    Modules linked in:
    CPU: 0 PID: 282 Comm: kms_cursor_lega Tainted: G W 5.19.0-rc2-15930-g875cc8bc536a #1
    Hardware name: Qualcomm Technologies, Inc. DB820c (DT)
    pstate: 60000005 (nZCv daif -PAN -UAO -TCO -DIT -SSBS BTYPE=--)
    pc : drm_modeset_lock+0xf8/0x154
    lr : drm_atomic_get_private_obj_state+0x84/0x170
    sp : ffff80000cfab6a0
    x29: ffff80000cfab6a0 x28: 0000000000000000 x27: ffff000083bc4d00
    x26: 0000000000000038 x25: 0000000000000000 x24: ffff80000957ca58
    x23: 0000000000000000 x22: ffff000081ace080 x21: 0000000000000001
    x20: ffff000081acec18 x19: ffff80000cfabb80 x18: 0000000000000038
    x17: 0000000000000000 x16: 0000000000000000 x15: fffffffffffea0d0
    x14: 0000000000000000 x13: 284e4f5f4e524157 x12: 5f534b434f4c5f47
    x11: ffff80000a386aa8 x10: 0000000000000029 x9 : ffff80000cfab610
    x8 : 0000000000000029 x7 : 0000000000000014 x6 : 0000000000000000
    x5 : 0000000000000001 x4 : ffff8000081ad904 x3 : 0000000000000029
    x2 : ffff0000801db4c0 x1 : ffff80000cfabb80 x0 : ffff000081aceb58
    Call trace:
    drm_modeset_lock+0xf8/0x154
    drm_atomic_get_private_obj_state+0x84/0x170
    mdp5_get_global_state+0x54/0x6c
    mdp5_pipe_release+0x2c/0xd4
    mdp5_plane_atomic_check+0x2ec/0x414
    drm_atomic_helper_check_planes+0xd8/0x210
    drm_atomic_helper_check+0x54/0xb0
    ...
    ---[ end trace 0000000000000000 ]---
    drm_modeset_lock attempting to lock a contended lock without backoff:
    drm_modeset_lock+0x148/0x154
    mdp5_get_global_state+0x30/0x6c
    mdp5_pipe_release+0x2c/0xd4
    mdp5_plane_atomic_check+0x290/0x414
    drm_atomic_helper_check_planes+0xd8/0x210
    drm_atomic_helper_check+0x54/0xb0
    drm_atomic_check_only+0x4b0/0x8f4
    drm_atomic_commit+0x68/0xe0

    Fixes: d59be579fa93 ("drm/msm/mdp5: Return error code in mdp5_pipe_release when deadlock is detected")
    Signed-off-by: Rob Clark <robdclark@chromium.org>
    Reviewed-by: Abhinav Kumar <quic_abhinavk@quicinc.com>
    Patchwork: https://patchwork.freedesktop.org/patch/492701/
    Link: https://lore.kernel.org/r/20220707162040.1594855-1-robdclark@gmail.com
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    drivers/gpu/drm/msm/disp/mdp5/mdp5_pipe.c | 3 ++-
    1 file changed, 2 insertions(+), 1 deletion(-)

    diff --git a/drivers/gpu/drm/msm/disp/mdp5/mdp5_pipe.c b/drivers/gpu/drm/msm/disp/mdp5/mdp5_pipe.c
    index 88de12225582..69fe09b41087 100644
    --- a/drivers/gpu/drm/msm/disp/mdp5/mdp5_pipe.c
    +++ b/drivers/gpu/drm/msm/disp/mdp5/mdp5_pipe.c
    @@ -134,12 +134,13 @@ int mdp5_pipe_release(struct drm_atomic_state *s, struct mdp5_hw_pipe *hwpipe)
    {
    struct msm_drm_private *priv = s->dev->dev_private;
    struct mdp5_kms *mdp5_kms = to_mdp5_kms(to_mdp_kms(priv->kms));
    - struct mdp5_global_state *state = mdp5_get_global_state(s);
    + struct mdp5_global_state *state;
    struct mdp5_hw_pipe_state *new_state;

    if (!hwpipe)
    return 0;

    + state = mdp5_get_global_state(s);
    if (IS_ERR(state))
    return PTR_ERR(state);

    --
    2.35.1


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