drm/amd/pm: fix race in power state check before mutex lock

The power state check in amdgpu_dpm_set_powergating_by_smu() is done
before acquiring the pm mutex, leading to a race condition where:
1. Thread A checks state and thinks no change is needed
2. Thread B acquires mutex and modifies the state
3. Thread A returns without updating state, causing inconsistency

Fix this by moving the mutex lock before the power state check,
ensuring atomicity of the state check and modification.

Fixes: 6ee27ee27ba8 ("drm/amd/pm: avoid duplicate powergate/ungate setting")
Signed-off-by: Yang Wang <kevinyang.wang@amd.com>
Reviewed-by: Kenneth Feng <kenneth.feng@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
(cherry picked from commit 7a3fbdfd19ec5992c0fc2d0bd83888644f5f2f38)

diff --git a/drivers/gpu/drm/amd/pm/amdgpu_dpm.c b/drivers/gpu/drm/amd/pm/amdgpu_dpm.c
index 79b174e5326da62da6980bb2dcdf8f20d2e1a643..302af1fb6901e78f891faddcbb2c3b1476b0c1e5 100644 (file)
--- a/drivers/gpu/drm/amd/pm/amdgpu_dpm.c
+++ b/drivers/gpu/drm/amd/pm/amdgpu_dpm.c
@@ -80,15 +80,15 @@ int amdgpu_dpm_set_powergating_by_smu(struct amdgpu_device *adev,
        enum ip_power_state pwr_state = gate ? POWER_STATE_OFF : POWER_STATE_ON;
        bool is_vcn = block_type == AMD_IP_BLOCK_TYPE_VCN;
 
+       mutex_lock(&adev->pm.mutex);
+
        if (atomic_read(&adev->pm.pwr_state[block_type]) == pwr_state &&
                        (!is_vcn || adev->vcn.num_vcn_inst == 1)) {
                dev_dbg(adev->dev, "IP block%d already in the target %s state!",
                                block_type, gate ? "gate" : "ungate");
-               return 0;
+               goto out_unlock;
        }
 
-       mutex_lock(&adev->pm.mutex);
-
        switch (block_type) {
        case AMD_IP_BLOCK_TYPE_UVD:
        case AMD_IP_BLOCK_TYPE_VCE:
@@ -115,6 +115,7 @@ int amdgpu_dpm_set_powergating_by_smu(struct amdgpu_device *adev,
        if (!ret)
                atomic_set(&adev->pm.pwr_state[block_type], pwr_state);
 
+out_unlock:
        mutex_unlock(&adev->pm.mutex);
 
        return ret;