[RFC PATCH 07/10] arm64/sve: Add vector length inheritance control

Dave Martin Dave.Martin@arm.com
Mon Jan 16 13:34:00 GMT 2017


On Mon, Jan 16, 2017 at 12:27:55PM +0000, Yao Qi wrote:
> On 17-01-12 11:26:06, Dave Martin wrote:
> > Currently the vector length is inherited across both fork() and
> > exec().
> > 
> > Inheritance across fork() is desirable both for creating a copy of
> > a process (traditional fork) or creating a thread (where we want
> > all threads to share the same VL by default).
> > 
> > Inheritance across exec() is less desirable, because of the ABI
> > impact of large vector lengths on the size of the signal frame --
> > when running a new binary, there is no guarantee that the new
> > binary is compatible with these ABI changes.
> > 
> > This flag makes the vector length non-inherited by default.
> 
> Can we make vector length inherited across fork but non-inherited
> across exec by default?

That is the behaviour: I always inherit across fork/clone, since
you are still running the same binary after those.

I could word the commit message a bit more clearly here.

Cheers
---Dave 



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