Re: [Patch 0/2] Separate semaphore container.

[Laszlo Ersek <lersek@redhat.com>]

On 11/10/18 04:19, Dong, Eric wrote:
> Hi Stewards:
>  
> Since this is a bug fix, and the risk for this release is small. I plan to push this serial changes before edk2-stable201811 tag.
> 
> If you have any concern, please raise here. 

I'm fine with pushing this, as I explained elsewhere in this thread:

https://www.mail-archive.com/edk2-devel@lists.01.org/msg46898.html

"Also this looks like a bugfix to a new feature already committed in
this development cycle, so I think it may go in during the hard feature
freeze."

Thanks
Laszlo

>> -----Original Message-----
>> From: edk2-devel [mailto:edk2-devel-bounces@lists.01.org] On Behalf Of Eric
>> Dong
>> Sent: Thursday, November 8, 2018 10:58 AM
>> To: edk2-devel@lists.01.org
>> Cc: Ni, Ruiyu <ruiyu.ni@intel.com>; Laszlo Ersek <lersek@redhat.com>
>> Subject: [edk2] [Patch 0/2] Separate semaphore container.
>>
>> In current implementation, core level semaphore use same container with
>> package level semaphore. This design will let the core level semaphore not
>> works as expected in below case:
>> 1. Feature A has CPU_FEATURE_CORE_BEFORE dependence with Feature B.
>> 2. Feature C has CPU_FEATURE_PACKAGE_AFTER dependence with Feature B.
>> in this case an core level semaphore will be add between A and B, and an
>> package level semaphore will be add between B and C.
>>
>> For a CPU has one package, two cores and 4 threads. Execute like below:
>>
>>   Thread 1          Thread 2    .....     Thread 4
>> ReleaseSemaph(1,2)  -|
>> WaitForSemaph(1(2)) -|<-----------------------These two are Core Semaph
>>                   ReleaseSemaph(1,2) -|
>>                   WaitForSemaph(2)   -| <---  Core Semaph
>>
>> ReleaseSemaph (1,2,3,4) -|
>> WaitForSemaph (1(4))    -| <----------------  Package Semaph
>>
>>                                       ReleaseSemaph(3,4)
>>                                       WaitForSemaph(4(2)) <- Core Semaph
>>
>> In above case, for thread 4, when it executes a core semaphore, i will found
>> WaitForSemaph(4(2)) is met because Thread 1 has execute a package
>> semaphore and ReleaseSemaph(4) for it before. This is not an expect behavior.
>> Thread 4 should wait for thread 3 to do this.
>>
>> Fix this issue by separate the semaphore container for core level and package
>> level.
>>
>> Cc: Laszlo Ersek <lersek@redhat.com>
>> Cc: Ruiyu Ni <ruiyu.ni@intel.com>
>> Contributed-under: TianoCore Contribution Agreement 1.1
>> Signed-off-by: Eric Dong <eric.dong@intel.com>
>>
>> Eric Dong (2):
>>   UefiCpuPkg/RegisterCpuFeaturesLib: Separate semaphore container.
>>   UefiCpuPkg/PiSmmCpuDxeSmm: Separate semaphore container.
>>
>>  .../RegisterCpuFeaturesLib/CpuFeaturesInitialize.c  |  9 ++++++---
>>  .../RegisterCpuFeaturesLib/RegisterCpuFeatures.h    |  7 ++++---
>>  UefiCpuPkg/PiSmmCpuDxeSmm/CpuS3.c                   | 21 ++++++++++++++-------
>>  3 files changed, 24 insertions(+), 13 deletions(-)
>>
>> --
>> 2.15.0.windows.1
>>
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