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Re: [RFC PATCH 07/10] arm64/sve: Add vector length inheritance control
- From: Dave Martin <Dave dot Martin at arm dot com>
- To: Yao Qi <qiyaoltc at gmail dot com>
- Cc: linux-arch at vger dot kernel dot org, Florian Weimer <fweimer at redhat dot com>, libc-alpha at sourceware dot org, Ard Biesheuvel <ard dot biesheuvel at linaro dot org>, Marc Zyngier <Marc dot Zyngier at arm dot com>, gdb at sourceware dot org, Joseph Myers <joseph at codesourcery dot com>, Szabolcs Nagy <szabolcs dot nagy at arm dot com>, linux-arm-kernel at lists dot infradead dot org, Alan Hayward <alan dot hayward at arm dot com>, Torvald Riegel <triegel at redhat dot com>, Christoffer Dall <christoffer dot dall at linaro dot org>
- Date: Mon, 16 Jan 2017 13:34:44 +0000
- Subject: Re: [RFC PATCH 07/10] arm64/sve: Add vector length inheritance control
- Authentication-results: sourceware.org; auth=none
- References: <1484220369-23970-1-git-send-email-Dave.Martin@arm.com> <1484220369-23970-8-git-send-email-Dave.Martin@arm.com> <20170116122755.GH28060@E107787-LIN>
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