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Subject: Re: [edk2-devel] [PATCH] MdePkg: use CpuPause() in CpuDeadLoop()
To: devel@edk2.groups.io, ankur.a.arora@oracle.com
Cc: Liming Gao <gaoliming@byosoft.com.cn>,
 Michael D Kinney <michael.d.kinney@intel.com>
References: <20210316225918.2625938-1-ankur.a.arora@oracle.com>
From: "Laszlo Ersek" <lersek@redhat.com>
Message-ID: <2212bc34-f8b5-fd65-aa2e-c91b7b97915c@redhat.com>
Date: Wed, 17 Mar 2021 19:30:55 +0100
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On 03/16/21 23:59, Ankur Arora wrote:
> Use CpuPause() to allow the CPU to go into a lower power state
> state while we spin wait.
> 
> Cc: Liming Gao <gaoliming@byosoft.com.cn>
> Signed-off-by: Ankur Arora <ankur.a.arora@oracle.com>
> Reviewed-by: Michael D Kinney <michael.d.kinney@intel.com>
> ---
>  MdePkg/Library/BaseLib/CpuDeadLoop.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/MdePkg/Library/BaseLib/CpuDeadLoop.c b/MdePkg/Library/BaseLib/CpuDeadLoop.c
> index 9e110cacbc96..3cd304351a65 100644
> --- a/MdePkg/Library/BaseLib/CpuDeadLoop.c
> +++ b/MdePkg/Library/BaseLib/CpuDeadLoop.c
> @@ -28,5 +28,7 @@ CpuDeadLoop (
>  {
>    volatile UINTN  Index;
>  
> -  for (Index = 0; Index == 0;);
> +  for (Index = 0; Index == 0;) {
> +    CpuPause();
> +  }
>  }
> 

Reviewed-by: Laszlo Ersek <lersek@redhat.com>

(for RISC-V and ARM64, the implementations seem to be "nop" instructions)

Thanks
Laszlo