Re: [PATCH 2/2] x86/asm/delay: Introduce TPAUSE delay

[Luck, Tony]

On Wed, Feb 26, 2020 at 01:10:40PM -0800, Andi Kleen wrote:
> On Wed, Feb 26, 2020 at 11:10:58AM -0800, Kyung Min Park wrote:
> > TPAUSE instructs the processor to enter an implementation-dependent
> > optimized state. The instruction execution wakes up when the time-stamp
> > counter reaches or exceeds the implicit EDX:EAX 64-bit input value.
> > The instruction execution also wakes up due to the expiration of
> > the operating system time-limit or by an external interrupt
> 
> This is actually a behavior change. Today's udelay() will continue
> after processing the interrupt. Your patches don't

The instruction level TPAUSE is called inside delay_wait()
that checks to see of we were interrupted early and loops to issue
another TPAUSE if needed.

-Tony