(In reply to Alex Deucher from comment #1)
> This is more likely a mesa issue than a kernel issue.

no, 4.14 kernel with latest mesa libs works very vell without any stucks
but from 4.20.4 and in all latest kernels (including 5.0) OS freezes and stucks every 30s ... 1min for 30s when browsing youtube with HW acceleration enabled(uvd) or playing a game, RX550, Arch, vanilla kernel

  365.021164] amdgpu: [powerplay] 
                last message was failed ret is 0
[  365.045198] [drm:amdgpu_job_timedout [amdgpu]] *ERROR* ring gfx timeout, but soft recovered
[  365.570667] amdgpu: [powerplay] 
                failed to send message 133 ret is 0 
[  366.115228] [drm:amdgpu_job_timedout [amdgpu]] *ERROR* ring sdma0 timeout, signaled seq=9365, emitted seq=9365
[  366.115377] [drm:amdgpu_job_timedout [amdgpu]] *ERROR* Process information: process  pid 0 thread  pid 0
[  366.115388] [drm] Timeout, but no hardware hang detected.
[  366.689407] amdgpu: [powerplay] 
                last message was failed ret is 0
[  367.232287] amdgpu: [powerplay] 
                failed to send message 306 ret is 0 
[  367.787043] amdgpu: [powerplay] 
                last message was failed ret is 0
[  368.320138] amdgpu: [powerplay] 
                failed to send message 5e ret is 0 
[  369.367739] amdgpu: [powerplay] 
                last message was failed ret is 0
[  369.907559] amdgpu: [powerplay] 
                failed to send message 145 ret is 0 
[  370.994478] amdgpu: [powerplay] 
                last message was failed ret is 0
[  371.538753] amdgpu: [powerplay] 
                failed to send message 146 ret is 0 
[  372.075079] amdgpu: [powerplay] 
                last message was failed ret is 0
[  372.598565] amdgpu: [powerplay] 
                failed to send message 148 ret is 0 
[  373.657188] amdgpu: [powerplay] 
                last message was failed ret is 0
[  374.198637] amdgpu: [powerplay] 
                failed to send message 145 ret is 0 
[  375.075076] [drm:amdgpu_job_timedout [amdgpu]] *ERROR* ring gfx timeout, but soft recovered
[  375.284948] amdgpu: [powerplay] 
                last message was failed ret is 0
[  375.830347] amdgpu: [powerplay] 
                failed to send message 146 ret is 0 
[  376.138428] [drm:amdgpu_job_timedout [amdgpu]] *ERROR* ring sdma0 timeout, signaled seq=10113, emitted seq=10113
[  376.138783] [drm:amdgpu_job_timedout [amdgpu]] *ERROR* Process information: process  pid 0 thread  pid 0
[  376.138797] [drm] IP block:sdma_v3_0 is hung!
[  376.138809] [drm] GPU recovery disabled.
[  376.394657] amdgpu: [powerplay] 
                last message was failed ret is 0
[  376.934375] amdgpu: [powerplay] 
                failed to send message 16a ret is 0 
[  377.463230] amdgpu: [powerplay] 
                last message was failed ret is 0
[  377.977725] amdgpu: [powerplay] 
                failed to send message 186 ret is 0 
[  378.518406] amdgpu: [powerplay] 
                last message was failed ret is 0
[  379.060098] amdgpu: [powerplay] 
                failed to send message 54 ret is 0 
[  379.556880] amdgpu: [powerplay] 
                last message was failed ret is 0
[  380.075217] amdgpu: [powerplay] 
                failed to send message 26b ret is 0 
[  380.605976] amdgpu: [powerplay] 
                last message was failed ret is 0
[  381.134301] amdgpu: [powerplay] 
                failed to send message 13d ret is 0 
[  381.657486] amdgpu: [powerplay] 
                last message was failed ret is 0
[  382.204551] amdgpu: [powerplay] 
                failed to send message 14f ret is 0 
[  382.741827] amdgpu: [powerplay] 
                last message was failed ret is 0
[  383.281165] amdgpu: [powerplay] 
                failed to send message 151 ret is 0 
[  383.824923] amdgpu: [powerplay] 
                last message was failed ret is 0
[  384.362266] amdgpu: [powerplay] 
                failed to send message 135 ret is 0 
[  384.903686] amdgpu: [powerplay] 
                last message was failed ret is 0
[  385.101515] [drm:amdgpu_job_timedout [amdgpu]] *ERROR* ring gfx timeout, but soft recovered
[  385.461515] amdgpu: [powerplay] 
                failed to send message 190 ret is 0 
[  386.014015] amdgpu: [powerplay] 
                last message was failed ret is 0
[  386.164818] [drm:amdgpu_job_timedout [amdgpu]] *ERROR* ring sdma0 timeout, signaled seq=10761, emitted seq=10761
[  386.164970] [drm:amdgpu_job_timedout [amdgpu]] *ERROR* Process information: process  pid 0 thread  pid 0
[  386.164985] [drm] Timeout, but no hardware hang detected.