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

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Date: Wed, 10 Jan 2024 11:08:29 -0800
From: Randy Dunlap <rdunlap@...radead.org>
To: Andrea Parri <parri.andrea@...il.com>
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



On 1/10/24 11:05, Andrea Parri wrote:
> 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.

I see.

> 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 [...]"
                                                                            _EXPEDITED

OK, that's better IMO. Thanks.

-- 
#Randy