Sorry I didn't add the BZ link.
https://bugzilla.tianocore.org/show_bug.cgi?id=1400
"If an interrupt happens between CheckEvent and gIdleLoopEvent, there would be
a event pending during cpu sleep."
Here is the wait for event flow:
Result = CheckEvent
(interrupt happens here, and set the gEventPending)
Result == FALSE
Ilde event (put cpu to sleep)(there are events in pending list and they should
be handle, but the cpu is hlt and cannot handle it)
Solution is here:
Result = CheckEvent
(interrupt happens)
Disable interrupt
PendingResult = Check gEventPending
If gEventPending == TRUE {
Enable interrupt and goto CheckEvent to handle
} else {
Enable interrupt and hlt (this should be 'atomic' so that no race condition
would happen)
}
Thanks,
Zhichao
> -----Original Message-----
> From: Ni, Ray
> Sent: Friday, May 24, 2019 1:18 PM
> To: Gao, Zhichao <zhichao....@intel.com>; devel@edk2.groups.io
> Cc: Wang, Jian J <jian.j.w...@intel.com>; Wu, Hao A <hao.a...@intel.com>;
> Zeng, Star <star.z...@intel.com>; Gao, Liming <liming....@intel.com>;
> Sean Brogan <sean.bro...@microsoft.com>; Michael Turner
> <michael.tur...@microsoft.com>; Bret Barkelew
> <bret.barke...@microsoft.com>; Kinney, Michael D
> <michael.d.kin...@intel.com>; Dong, Eric <eric.d...@intel.com>; Laszlo
> Ersek <ler...@redhat.com>
> Subject: RE: [PATCH 0/6] Fix race condition and add event protocol
>
> Zhichao,
> Did your detailed patch commit message describe the consequence of the
> race condition? (I haven't checked.) If no, could you please describe in
> detail
> about the consequence?
>
> Thanks,
> Ray
>
> > -----Original Message-----
> > From: Gao, Zhichao
> > Sent: Friday, May 24, 2019 1:05 PM
> > To: devel@edk2.groups.io
> > Cc: Wang, Jian J <jian.j.w...@intel.com>; Wu, Hao A
> > <hao.a...@intel.com>; Ni, Ray <ray...@intel.com>; Zeng, Star
> > <star.z...@intel.com>; Gao, Liming <liming....@intel.com>; Sean Brogan
> > <sean.bro...@microsoft.com>; Michael Turner
> > <michael.tur...@microsoft.com>; Bret Barkelew
> > <bret.barke...@microsoft.com>; Kinney, Michael D
> > <michael.d.kin...@intel.com>; Dong, Eric <eric.d...@intel.com>; Laszlo
> > Ersek <ler...@redhat.com>
> > Subject: [PATCH 0/6] Fix race condition and add event protocol
> >
> > There is a race condition in CoreWaitForEvent function:
> > If an interrupt happens between CheckEvent and gIdleLoopEvent, there
> > would be a event pending during cpu sleep.
> > So it is required to check the gEventPending with the interrupt disabled.
> > Implement a gEfiCpu2ProtocolGuid to fix that. The protocol include one
> > interface to enable interrupt and put the cpu to sleep.
> >
> > Add a event protocol gEdkiiCommonEventProtocolGuid to support all TPL
> > event. It is require for PI drivers that use HW interrput.
> >
> > Cc: Jian J Wang <jian.j.w...@intel.com>
> > Cc: Hao A Wu <hao.a...@intel.com>
> > cc: Ray Ni <ray...@intel.com>
> > Cc: Star Zeng <star.z...@intel.com>
> > Cc: Liming gao <liming....@intel.com>
> > Cc: Sean Brogan <sean.bro...@microsoft.com>
> > Cc: Michael Turner <michael.tur...@microsoft.com>
> > Cc: Bret Barkelew <bret.barke...@microsoft.com>
> > Cc: Michael D Kinney <michael.d.kin...@intel.com>
> > Cc: Eric Dong <eric.d...@intel.com>
> > Cc: Laszlo Ersek <ler...@redhat.com>
> >
> > Sean Brogan (5):
> > MdeModulePkg: Add gEdkiiCommonEventProtocolGuid for event
> > MdePkg/BaseLib.h: Add EnableInterruptsAndSleep function declare
> > MdePkg/BaseLib: Implement EnableInterruptsAndSleep
> > MdePkg: Add gEfiCpu2ProtocolGuid and header file
> > MdeModulePkg/DxeMain: Implement common event protocol
> >
> > Zhichao Gao (1):
> > UefiCpuPkg/CpuDxe: Implement Cpu2 protocol
> >
> > MdeModulePkg/Core/Dxe/DxeMain.h | 64 ++++++++++-
> > MdeModulePkg/Core/Dxe/DxeMain.inf | 1 +
> > MdeModulePkg/Core/Dxe/DxeMain/DxeMain.c | 22 ++++
> > .../Core/Dxe/DxeMain/DxeProtocolNotify.c | 1 +
> > MdeModulePkg/Core/Dxe/Event/Event.c | 102 ++++++++++++++++-
> -
> > MdeModulePkg/Core/Dxe/Event/Event.h | 2 +-
> > MdeModulePkg/Include/Protocol/CommonEvent.h | 18 ++++
> > MdeModulePkg/MdeModulePkg.dec | 3 +
> > MdePkg/Include/Library/BaseLib.h | 11 ++
> > MdePkg/Include/Protocol/Cpu2.h | 43 ++++++++
> > .../Library/BaseLib/Ia32/EnableInterrupts.c | 18 +++-
> > .../BaseLib/Ia32/EnableInterrupts.nasm | 15 ++-
> > .../Library/BaseLib/X64/EnableInterrupts.nasm | 15 ++-
> > MdePkg/MdePkg.dec | 3 +
> > UefiCpuPkg/CpuDxe/CpuDxe.c | 40 ++++++-
> > UefiCpuPkg/CpuDxe/CpuDxe.h | 15 +++
> > UefiCpuPkg/CpuDxe/CpuDxe.inf | 3 +-
> > 17 files changed, 358 insertions(+), 18 deletions(-) create mode
> > 100644 MdeModulePkg/Include/Protocol/CommonEvent.h
> > create mode 100644 MdePkg/Include/Protocol/Cpu2.h
> >
> > --
> > 2.21.0.windows.1
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