RE: [PATCH v2 1/2] iopoll: Call cpu_relax() in busy loops

[David Laight]

From: Tony Lindgren
> Sent: 11 May 2023 07:49
> 
> * Geert Uytterhoeven <geert+renesas@xxxxxxxxx> [230510 13:23]:
> > It is considered good practice to call cpu_relax() in busy loops, see
> > Documentation/process/volatile-considered-harmful.rst.  This can not
> > only lower CPU power consumption or yield to a hyperthreaded twin
> > processor, but also allows an architecture to mitigate hardware issues
> > (e.g. ARM Erratum 754327 for Cortex-A9 prior to r2p0) in the
> > architecture-specific cpu_relax() implementation.

Don't you also need to call cond_resched() (at least some times).
Otherwise the process can't be pre-empted and a RT process
that last ran on that cpu will never be scheduled.

	David

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