Hi Eric, On 01/09/19 06:26, Dong, Eric wrote: > Hi all, > > We got some feedback about this BZ. Someone think this timeout is valuable > for the debug purpose, and oppose to remove it. > https://bugzilla.tianocore.org/show_bug.cgi?id=1419 > > So I'm back to here and want to still use this change. I not use "update > PcdSpinLockTimeout to 0 in platform" solution because I think core driver > depends on platform policy is not a good design. > > Do you guys have any other concern?
sorry, I don't understand. (1) In <https://bugzilla.tianocore.org/show_bug.cgi?id=1419>, where currently comment #2 is the last comment, I don't see any request for keeping the timeout facility. (2) On the mailing list as well, you seem to have received comments only in favor of removing the timeout facility. "Someone think this timeout is valuable for the debug purpose" doesn't cut it, for open development. I don't care about the identity of the person that wants to preserve the feature, but I certainly care about their use case. You shouldn't have to mediate and describe their use case for them, on the list; that's always a lossy process. Regarding the PCD: I think zeroing "PcdSpinLockTimeout" to disable the timeout case is a valid approach, it's just that we should change the default value in the DEC file to zero. Then the PCD setting will become a burden only for those platforms and those use cases that want to use the timeout feature (such as for debugging). In general, PCD default values in DEC files have to be considered carefully, but in some cases, such changes are the right thing. Another example was 509f8425b75d ("UefiCpuPkg: change PcdCpuSmmStackGuard default to TRUE", 2016-06-06). (You made the same point at the end of <https://bugzilla.tianocore.org/show_bug.cgi?id=1419#c2>.) In addition to changing the default value to zero, I'd suggest moving "PcdSpinLockTimeout" from section [PcdsFixedAtBuild,PcdsPatchableInModule] to section [PcdsFixedAtBuild, PcdsPatchableInModule, PcdsDynamic, PcdsDynamicEx] so that platforms can enable the "debug" feature (i.e. set a nonzero value) more flexibly. Thanks Laszlo >> -----Original Message----- >> From: Brian J. Johnson [mailto:[email protected]] >> Sent: Friday, December 21, 2018 12:36 AM >> To: Yao, Jiewen <[email protected]>; Ni, Ruiyu <[email protected]>; >> Dong, Eric <[email protected]>; [email protected] >> Cc: Laszlo Ersek <[email protected]> >> Subject: Re: [edk2] [Patch 1/3] UefiCpuPkg/RegisterCpuFeaturesLib: Avoid >> AP calls PeiService. >> >> Agreed. We've seen issues on real platforms with timed-out spinlocks in DXE >> causing calls to GetPerformanceCounter and DebugAssert. (DXE has the >> same code, with the same issues.) >> >> Note that it's possible to set PcdSpinLockTimeout=0 to work around the issue >> on a particular platform, or in a particular module. But if you have to do >> that >> for every module which uses APs, and hence could contend for a spinlock, it >> kind of defeats the point.... We're better off removing the timeout code. >> >> Thanks, >> Brian >> >> On 12/19/18 8:08 PM, Yao, Jiewen wrote: >>> Yes, I agree, if we don't have any real case. >>> >>> >>>> -----Original Message----- >>>> From: Ni, Ruiyu >>>> Sent: Thursday, December 20, 2018 10:07 AM >>>> To: Dong, Eric <[email protected]>; Yao, Jiewen >>>> <[email protected]>; [email protected] >>>> Cc: Laszlo Ersek <[email protected]> >>>> Subject: RE: [edk2] [Patch 1/3] UefiCpuPkg/RegisterCpuFeaturesLib: >>>> Avoid AP calls PeiService. >>>> >>>> Can you just change the AcquireSpinLock() behavior to remove the >>>> Timeout PCD consumption? >>>> >>>> I haven't seen a real case that the timed acquisition of spin lock is >>>> needed. >>>> >>>> >>>> Thanks/Ray >>>> >>>>> -----Original Message----- >>>>> From: Dong, Eric <[email protected]> >>>>> Sent: Thursday, December 20, 2018 9:23 AM >>>>> To: Yao, Jiewen <[email protected]>; [email protected] >>>>> Cc: Ni, Ruiyu <[email protected]>; Laszlo Ersek <[email protected]> >>>>> Subject: RE: [edk2] [Patch 1/3] UefiCpuPkg/RegisterCpuFeaturesLib: >>>>> Avoid AP calls PeiService. >>>>> >>>>> >>>>> Agreed, Maybe it's time to add a new API like >>>>> AcquireSpinLockWithoutTimeOut? >>>>> >>>>> Thanks, >>>>> Eric >>>>>> -----Original Message----- >>>>>> From: Yao, Jiewen >>>>>> Sent: Thursday, December 20, 2018 9:19 AM >>>>>> To: Dong, Eric <[email protected]>; [email protected] >>>>>> Cc: Ni, Ruiyu <[email protected]>; Laszlo Ersek >>>>>> <[email protected]> >>>>>> Subject: RE: [edk2] [Patch 1/3] UefiCpuPkg/RegisterCpuFeaturesLib: >>>>>> Avoid AP calls PeiService. >>>>>> >>>>>> Hi >>>>>> If we think below code is generic, can we have an API for that? >>>>>> >>>>>> + // >>>>>> + // Wait for the AP to release the MSR spin lock. >>>>>> + // >>>>>> + while (!AcquireSpinLockOrFail (&CpuFlags->ConsoleLogLock)) { >>>>>> + CpuPause (); >>>>>> + } >>>>>> >>>>>> >>>>>> >>>>>> >>>>>>> -----Original Message----- >>>>>>> From: edk2-devel [mailto:[email protected]] On >>>>>>> Behalf Of Eric Dong >>>>>>> Sent: Thursday, December 20, 2018 9:16 AM >>>>>>> To: [email protected] >>>>>>> Cc: Ni, Ruiyu <[email protected]>; Laszlo Ersek >>>>>>> <[email protected]> >>>>>>> Subject: [edk2] [Patch 1/3] UefiCpuPkg/RegisterCpuFeaturesLib: >>>>>>> Avoid AP calls PeiService. >>>>>>> >>>>>>> In AcquireSpinLock function, it calls GetPerformanceCounter which >>>>>>> final calls PeiService service. This patch avoid to call >>>>>>> AcquireSpinLock function. >>>>>>> >>>>>>> BZ: https://bugzilla.tianocore.org/show_bug.cgi?id=1411 >>>>>>> >>>>>>> Cc: Ruiyu Ni <[email protected]> >>>>>>> Cc: Laszlo Ersek <[email protected]> >>>>>>> Contributed-under: TianoCore Contribution Agreement 1.1 >>>>>>> Signed-off-by: Eric Dong <[email protected]> >>>>>>> --- >>>>>>> >>>>>>> UefiCpuPkg/Library/RegisterCpuFeaturesLib/CpuFeaturesInitialize.c >>>>>>> | >>>>>>> 7 >>>>>>> ++++++- >>>>>>> 1 file changed, 6 insertions(+), 1 deletion(-) >>>>>>> >>>>>>> diff --git >>>>>>> a/UefiCpuPkg/Library/RegisterCpuFeaturesLib/CpuFeaturesInitialize. >>>>>>> c >>>>>>> b/UefiCpuPkg/Library/RegisterCpuFeaturesLib/CpuFeaturesInitialize. >>>>>>> c index 624ddee055..a64326239f 100644 >>>>>>> --- >>>>>>> a/UefiCpuPkg/Library/RegisterCpuFeaturesLib/CpuFeaturesInitialize. >>>>>>> c >>>>>>> +++ >>>> b/UefiCpuPkg/Library/RegisterCpuFeaturesLib/CpuFeaturesInitialize. >>>>>>> +++ c >>>>>>> @@ -832,7 +832,12 @@ ProgramProcessorRegister ( >>>>>>> RegisterTableEntry = &RegisterTableEntryHead[Index]; >>>>>>> >>>>>>> DEBUG_CODE_BEGIN (); >>>>>>> - AcquireSpinLock (&CpuFlags->ConsoleLogLock); >>>>>>> + // >>>>>>> + // Wait for the AP to release the MSR spin lock. >>>>>>> + // >>>>>>> + while (!AcquireSpinLockOrFail (&CpuFlags->ConsoleLogLock)) { >>>>>>> + CpuPause (); >>>>>>> + } >>>>>>> ThreadIndex = ApLocation->Package * >>>> CpuStatus->MaxCoreCount * >>>>>>> CpuStatus->MaxThreadCount + >>>>>>> ApLocation->Core * CpuStatus->MaxThreadCount + >>>>>>> ApLocation->Thread; >>>>>>> -- >>>>>>> 2.15.0.windows.1 >>>>>>> >>>>>>> _______________________________________________ >>>>>>> edk2-devel mailing list >>>>>>> [email protected] >>>>>>> https://lists.01.org/mailman/listinfo/edk2-devel >>> _______________________________________________ >>> edk2-devel mailing list >>> [email protected] >>> https://lists.01.org/mailman/listinfo/edk2-devel >>> >> >> >> -- >> Brian J. Johnson >> Enterprise X86 Lab >> >> Hewlett Packard Enterprise >> >> [email protected] > _______________________________________________ edk2-devel mailing list [email protected] https://lists.01.org/mailman/listinfo/edk2-devel
