linux-kernel - Re: [lkp-robot] [x86/asm] f5caf621ee: PANIC:double

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Message-ID: <20170928084941.ygmvb6qfn3otfvac@gmail.com>
Date:   Thu, 28 Sep 2017 10:49:41 +0200
From:   Ingo Molnar <mingo@...nel.org>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     kernel test robot <xiaolong.ye@...el.com>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Andrey Ryabinin <aryabinin@...tuozzo.com>,
        Matthias Kaehlcke <mka@...omium.org>,
        Alexander Potapenko <glider@...gle.com>,
        Andy Lutomirski <luto@...nel.org>,
        Arnd Bergmann <arnd@...db.de>,
        Dmitriy Vyukov <dvyukov@...gle.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Miguel Bernal Marin <miguel.bernal.marin@...ux.intel.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        LKML <linux-kernel@...r.kernel.org>, lkp@...org
Subject: Re: [lkp-robot] [x86/asm]  f5caf621ee: PANIC:double_fault


* Peter Zijlstra <peterz@...radead.org> wrote:

> On Thu, Sep 28, 2017 at 09:59:07AM +0200, Ingo Molnar wrote:
> > 
> > * kernel test robot <xiaolong.ye@...el.com> wrote:
> > 
> > > 
> > > FYI, we noticed the following commit:
> > > 
> > > commit: f5caf621ee357279e759c0911daf6d55c7d36f03 ("x86/asm: Fix inline asm call constraints for Clang")
> > > https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git master
> > > 
> > > in testcase: trinity
> > > with following parameters:
> > > 
> > > 	runtime: 300s
> > > 
> > > test-description: Trinity is a linux system call fuzz tester.
> > > test-url: http://codemonkey.org.uk/projects/trinity/
> > > 
> > > 
> > > on test machine: qemu-system-x86_64 -enable-kvm -m 420M
> > > 
> > > caused below changes (please refer to attached dmesg/kmsg for entire log/backtrace):
> > > 
> > > 
> > > +-----------------------------------------+------------+------------+
> > > |                                         | 0d0970eef3 | f5caf621ee |
> > > +-----------------------------------------+------------+------------+
> > > | boot_successes                          | 9          | 4          |
> > > | boot_failures                           | 0          | 4          |
> > > | PANIC:double_fault                      | 0          | 4          |
> > > | Kernel_panic-not_syncing:Machine_halted | 0          | 4          |
> > > +-----------------------------------------+------------+------------+
> > 
> > I think a key piece of information is that the test is using GCC 4.4:
> > 
> >         export compiler='gcc-4.4'
> > 
> > ... which is pretty old compared to what gets tested typically.
> > 
> > GCC 4.4 was released in 2009 (!), the last minor update of 4.4.7 was 5 years ago.
> 
> Sure, but its still an officially supported GCC version. So either it
> must be made to work, or we must update the minimal GCC version
> requirements for the kernel.

Of course! I just mean I'd not be surprised if this was a GCC bug/quirk
with legacy GCC versions that probably won't be fixed.

Thanks,

	Ingo