linux-kernel - Re: [PATCHv2] ARM64:Fix MINSIGSTKSZ and SIGSTKSZ

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Message-ID: <20151012135300.GA26786@e103592.cambridge.arm.com>
Date:	Mon, 12 Oct 2015 14:53:13 +0100
From:	Dave Martin <Dave.Martin@....com>
To:	Arnd Bergmann <arnd@...db.de>
Cc:	linux-arm-kernel@...ts.infradead.org, catalin.marinas@....com,
	will.deacon@....com, linux-kernel@...r.kernel.org,
	Akhilesh Kumar <akhilesh.k@...sung.com>,
	Rohit Thapliyal <r.thapliyal@...sung.com>,
	Andreas Schwab <schwab@...e.de>,
	Manjeet Pawar <manjeet.p@...sung.com>, pankaj.m@...sung.com
Subject: Re: [PATCHv2] ARM64:Fix MINSIGSTKSZ and SIGSTKSZ

On Fri, Oct 09, 2015 at 10:41:43AM +0200, Arnd Bergmann wrote:
> On Tuesday 06 October 2015 12:51:24 Arnd Bergmann wrote:
> > 
> > I think it makes sense to stick with the traditional definition
> > of MINSIGSTKSZ == "the minimum amount that you will always need,
> > add whatever you require yourself" and SIGSTKSZ == "Should be
> > enough for a couple of function calls". If we want to be conservative
> > in the kernel, using 8192 and 32768, to stay with the x4 ratio
> > that everyone else uses would be my first pick, though I'm not
> > particularly attached to those values.
> > 
> > 
> 
> On second thought, it really seems to late to make up our minds
> about the size now that glibc has already established 5KB as the
> minimum size. If we set it to 8KB/32KB, not just the testcase but
> real applications would start failing when they use the 5KB
> constant from glibc.

I agree for MINSIGSTKSZ.  We could still raise SIGSTKSZ if we think
that will be more future-proof (SIGSTKSZ would be less than the magic
4*MINSIGSTKSZ that most arches assume, unless SIGSTKSZ is made >=20KB).

Those might be independent changes.  The definition of MINSIGSTKSZ
is definitely broken right now, whereas SIGSTKSZ could be debated,
but isn't actually broken.

Cheers
---Dave

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