Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
Date:   Thu, 11 Jun 2020 18:10:22 +0200
From:   Peter Zijlstra <peterz@infradead.org>
To:     Chen Yu <yu.chen.surf@gmail.com>
Cc:     kernel test robot <rong.a.chen@intel.com>,
        Ingo Molnar <mingo@kernel.org>,
        LKML <linux-kernel@vger.kernel.org>, lkp@lists.01.org,
        Zhang Rui <rui.zhang@intel.com>
Subject: Re: [smp] b2a02fc43a: suspend-stress.fail
Message-ID: <20200611161022.GL2531@hirez.programming.kicks-ass.net>
References: <20200610083502.GF12456@shao2-debian>
 <20200610095054.GF2531@hirez.programming.kicks-ass.net>
 <CADjb_WSLpKrkt-Oq_3krGBp8ZLjVZ4caUAd0d0s1_6s1tOHdHQ@mail.gmail.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <CADjb_WSLpKrkt-Oq_3krGBp8ZLjVZ4caUAd0d0s1_6s1tOHdHQ@mail.gmail.com>
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

On Thu, Jun 11, 2020 at 04:24:53PM +0800, Chen Yu wrote:
> Hi Peter,
> On Wed, Jun 10, 2020 at 5:52 PM Peter Zijlstra <peterz@infradead.org> wrote:
> >
> > On Wed, Jun 10, 2020 at 04:35:02PM +0800, kernel test robot wrote:
> > > Greeting,
> > >
> > > FYI, we noticed the following commit (built with gcc-9):
> > >
> > > commit: b2a02fc43a1f40ef4eb2fb2b06357382608d4d84 ("smp: Optimize send_call_function_single_ipi()")
> > > https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git master
> > >
> > > in testcase: suspend-stress
> > > with following parameters:
> > >
> > >       mode: freeze
> > >       iterations: 10
> > >
> > >
> > >
> > > on test machine: 2 threads Broxton with 4G memory
> > >
> > > caused below changes (please refer to attached dmesg/kmsg for entire log/backtrace):
> > >
> > >
> > > If you fix the issue, kindly add following tag
> > > Reported-by: kernel test robot <rong.a.chen@intel.com>
> > >
> > >
> > > the result of this commit:
> > >
> > > test started
> >
> > No dmesg output? No splat?
> This issue was only found on one of the test machines from lkp team.
>  I've borrowed that machine and will try to narrow down and give feedback later.

Thanks! One thing to maybe try is hotplug tests. Suspend does hotplugs,
and it might be easier to debug hotplug than it is to debug suspend.