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Date:      Wed, 20 Dec 2017 10:16:58 -0800
From:      Nathan Whitehorn <nwhitehorn@freebsd.org>
To:        John Baldwin <jhb@freebsd.org>, David Chisnall <theraven@freebsd.org>
Cc:        Eugene Grosbein <eugen@grosbein.net>, Konstantin Belousov <kostikbel@gmail.com>, Conrad Meyer <cem@freebsd.org>, src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org
Subject:   Re: svn commit: r326758 - in head/sys/i386: conf include
Message-ID:  <28f2f06b-dc46-99f1-70be-260bb408c827@freebsd.org>
In-Reply-To: <1839614.eNG2DjLqvF@ralph.baldwin.cx>
References:  <201712110432.vBB4WbnE021090@repo.freebsd.org> <1705b795-46ca-bb27-6ba7-fab4eeed0aba@FreeBSD.org> <68FECEF0-014E-4741-BE96-680E9338557B@FreeBSD.org> <1839614.eNG2DjLqvF@ralph.baldwin.cx>

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On 12/20/17 09:14, John Baldwin wrote:
> On Wednesday, December 20, 2017 09:59:26 AM David Chisnall wrote:
>> On 16 Dec 2017, at 18:05, John Baldwin <jhb@FreeBSD.org> wrote:
>>> When I build a FreeBSD/mips64 kernel with clang,
>>> _any_ simple NFS op triggers a kernel stack overflow.  Kernels compiled
>>> with GCC do not.
>> That is not my experience.  I haven’t tried a MIPS64 kernel built with clang, but with in-tree gcc I get kernel panics as soon as I try to use NFS, unless I use Stacey’s patches that increase the kernel stack size.
> I have primarily been using modern GCC for GCC once that was working, but at
> least when running a MALTA64 kernel under qemu I was not triggering panics
> even with old GCC.  With the in-tree clang 5.0 or with CHERI clang, just
> doing an 'ls' of a NFS directory or even a tab-complete of a path that
> is on NFS reliably triggers a kernel stack overflow for MALTA64 in qemu.
>
> With Stacey's kstack pages, a clang kernel does survive, but those are not
> in stock FreeBSD which is where I have been testing this.
>

With GCC 4, it takes a little while, but trying to build ports over NFS 
is a sure-fire way to bring down the kernel. I haven't tried any other 
compilers.
-Nathan



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