Re: [PATCH -next] power/qos: fix a data race in pm_qos_*_value

On Feb 23, 2020, at 7:12 PM, Rafael J. Wysocki [off-list ref] wrote:

It may be a bug under certain conditions, but you don't mention what
conditions they are.  Reporting it as a general bug is not accurate at
the very least.

Could we rule out load tearing, store tearing and reload of global_req in cpuidle_governor_latency() for all compilers and architectures which could introduce logic bugs?

	int global_req = cpu_latency_qos_limit();

	if (device_req > global_req)
		device_req = global_req;

If under register pressure, the compiler might get ride of the tmp variable, i.e.,

If (device_req > cpu_latency_qos_limit())
—-> race with the writer.
         device_req = cpu_latency_qos_limit();