问题
I want to use the Windows User-Mode Scheduler API but every sample C or C++ I have found in the internet fails. Invariably I get ERROR_NOT_SUPPORTED.
My Computer is running Windows 10 Pro 64-bits in an x64 processor. I am using VS2015 and the application is an x64 console application.
Notably not every call fails, in the 4 samples I've tested either
- EnterUmsSchedulingMode
- CreateRemoteThreadEx
Fail with ERROR_NOT_SUPPORTED. Those are necessary to get things going, but for example CreateUmsCompletionList or GetUmsCompletionListEvent do not.
The API is not trivial to use but I am having a hard time believing all of them are wrong.
I've debugged a bit what happens inside EnterUmsSchedulingMode and it seems that things go wrong when calling NtSetInformationThread inside RtlpAttachThreadToUmsCompletionList although of this I am less sure.
Here is one and here is another of the samples I've tried.
回答1:
If you're on a pre-Ivy Bridge processor UMS will fail to work due to a potential security problem where an LDT is created on x64. The problem can be avoided with Ivy Bridge and a Windows 10 (and ostensibly Server 2016) update simply disables the UMS feature if the processor doesn't have access to the Ivy Bridge feature.
More info here: http://www.alex-ionescu.com/?p=340
来源：https://stackoverflow.com/questions/34913794/user-mode-scheduler-ums-returns-error-not-supported