https://bugzilla.kernel.org/show_bug.cgi?id=110421

Bug ID: 110421 Summary: Reading debugfs file /sys/kernel/debug/dri/0/amdgpu_regs hangs the machine Product: Drivers Version: 2.5 Kernel Version: 4.4.0-0.rc8.git0.1.fc24.x86_64 Hardware: All OS: Linux Tree: Fedora Status: NEW Severity: high Priority: P1 Component: Video(DRI - non Intel) Assignee: drivers_video-dri@kernel-bugs.osdl.org Reporter: rivanvx@gmail.com Regression: No

I am using amdgpu driver on

01:00.0 VGA compatible controller [0300]: Advanced Micro Devices, Inc. [AMD/ATI] Amethyst XT [Radeon R9 M295X Mac Edition / R9 380X] [1002:6938] (rev f1)

Running the following script

for i in $(seq 0 65535); do echo -n "$i: "; dd if=amdgpu_regs bs=4 skip=$i count=1 2>/dev/null | hexdump -e '"%08x"'; echo; done

hangs the machine at register 14829 and the data from the register is not printed. I tried reading the registers twice just to be sure it hangs in the same place repeatedly, and it was 14829 in both cases.

I have reports this is reproducible using vanilla kernel.