Re: Semantics of smp_mb() [was : Re: [PATCH] Fix RCU race in access of nohz_cpu_mask ]

[Jesse Barnes <jbarnes@virtuousgeek.org>]

[Unknown author]
> > > From comments by jejb, we're looking at modifying the mmiowb
> > > API by adding an argument which would be a register to read
> > > from if the architecture in question needs ordering in this
> > > way but does not have a lighter weight mechanism like the Altix
> > > mmiowb.  Since there will now need to be a width indication,
> > > mmiowb will be replaced with mmiowb[bwlq].
> >
> > Any progress on this front?  I figured that I would wait to update
> > the ordering document until after this change happened, but if it
> > is going to be awhile, I should proceed with the current API.

I avoided doing this initially on the premise that I shouldn't do things 
'just because we might need it in the future' since that way seems to 
lead to madness.  Is there actual hardware that needs an argument to 
mmiowb() (i.e. that can't just do a read from the system's single bridge 
or something)?

Jesse
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