linux-kernel - Re: [PATCH v3 2/4] membarrier: Create Documentation/scheduler/membarrier.rst

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Date: Wed, 10 Jan 2024 20:05:44 +0100
From: Andrea Parri <parri.andrea@...il.com>
To: Randy Dunlap <rdunlap@...radead.org>
Cc: paul.walmsley@...ive.com, palmer@...belt.com, aou@...s.berkeley.edu,
	mathieu.desnoyers@...icios.com, paulmck@...nel.org, corbet@....net,
	mmaas@...gle.com, hboehm@...gle.com, striker@...ibm.com,
	charlie@...osinc.com, rehn@...osinc.com,
	linux-riscv@...ts.infradead.org, linux-doc@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 2/4] membarrier: Create
 Documentation/scheduler/membarrier.rst

Hi Randy,

> > +MEMBARRIER_CMD_{PRIVATE,GLOBAL}_EXPEDITED - Architecture requirements
> > +=====================================================================
> > +
> > +Memory barriers before updating rq->curr
> > +----------------------------------------
> > +
> > +The command requires each architecture to have a full memory barrier after
> > +coming from user-space, before updating rq->curr.  This barrier is implied
> > +by the sequence rq_lock(); smp_mb__after_spinlock() in __schedule().  The
> > +barrier matches a full barrier in the proximity of the membarrier system
> > +call exit, cf. membarrier_{private,global}_expedited().
> > +
> 
> What does "The command" refer to above and below, please?

The term was meant to refer to any of MEMBARRIER_CMD_PRIVATE_EXPEDITED and
MEMBARRIER_CMD_GLOBAL_EXPEDITED (from the section title); FWIW, this seems
to align with the terminology adopted in MEMBARRIER(2) for example.

Mmh, unless I get a better idea, I'll expand those occurrences to:

  "The commands MEMBARRIER_CMD_PRIVATE_EXPEDITED and MEMBARRIER_CMD_GLOBAL_EXPEDIDED
   require [...]"

  Andrea