Re: [Patch 1/2] UefiCpuPkg/RegisterCpuFeaturesLib: Separate semaphore container.

["Ni, Ruiyu" <ruiyu.ni@Intel.com>]

Eric,
Patch is good.
Reviewed-by: Ruiyu Ni <ruiyu.ni@intel.com>

Some modification to commit message to help understanding the changes.
Please rewording if you think some of them is not proper.

You can push the changes if no concerns about the new commit message.

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In current implementation, core and package level sync uses same 
semaphores. Sharing the semaphore may cause wrong execution order.
For example:
1. Feature A has CPU_FEATURE_CORE_BEFORE dependency with Feature B.
2. Feature C has CPU_FEATURE_PACKAGE_AFTER dependency with Feature B.
The expected feature initialization order is A B C:
A ---- (Core Depends) ----> B ---- (Package Depends) ----> C

For a CPU has 1 package, 2 cores and 4 threads. The feature 
initialization order may like below:

   Thread#1             Thread#2    Thread#3   Thread#4
   [A.Init]             [A.Init]               [A.Init]
Release(S1, S2)        Release(S1, S2)        Release(S3, S4)
Wait(S1) * 2           Wait(S2) * 2                        <- Core sync
   [B.Init]             [B.Init]
Release (S1,S2,S3,S4)
Wait (S1) * 4  <------------------------------------------ Package sync
                                               Wait(S4 * 2) <- Core sync
                                               [B.Init]

In above case, for thread#4, when it syncs in core level, Wait(S4) * 2 
isn't blocked and [B.Init] runs. But [A.Init] hasn't run in thread#3. 
It's wrong! Thread#4 should execute [B.Init] after thread#3 executes 
[A.Init] because B core level depends on A.

The reason is of the wrong execution order is that S4 is released in 
thread#1 by calling Release (S1, S2, S3, S4) and in thread #4 by calling 
Release (S3, S4).

To fix this issue, core level sync and package level sync should use 
separate semaphores.

In above example, the S4 released in Release (S1, S2, S3, S4) should not 
be the same semaphore as that in Release (S3, S4).

Thanks,
Ray