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:   Mon, 27 Apr 2020 18:54:10 +0300
From:   Leon Romanovsky <leon@kernel.org>
To:     Thomas Gleixner <tglx@linutronix.de>
Cc:     Ingo Molnar <mingo@kernel.org>, Ingo Molnar <mingo@redhat.com>,
        Borislav Petkov <bp@alien8.de>,
        "H. Peter Anvin" <hpa@zytor.com>, x86 <x86@kernel.org>,
        Suresh Siddha <suresh.b.siddha@intel.com>,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH] x86/apic: Fix circular locking dependency between
 console and hrtimer locks
Message-ID: <20200427155410.GG134660@unreal>
References: <20200407170925.1775019-1-leon@kernel.org>
 <20200414054836.GA956407@unreal>
 <20200414062454.GA84326@gmail.com>
 <87tv15qj5u.fsf@nanos.tec.linutronix.de>
 <20200427113218.GB134660@unreal>
 <87h7x5qe3v.fsf@nanos.tec.linutronix.de>
 <20200427134130.GE134660@unreal>
 <87y2qhoshi.fsf@nanos.tec.linutronix.de>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <87y2qhoshi.fsf@nanos.tec.linutronix.de>
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

On Mon, Apr 27, 2020 at 05:31:21PM +0200, Thomas Gleixner wrote:
> Leon Romanovsky <leon@kernel.org> writes:
> > OK, I consulted with verification people and back then the trigger was:
> > Reproduce when run "echo 1 > /sys/kernel/debug/clear_warn_once" after
> > reboot
>
> That explains it.
>
> > [    0.937310] Freeing SMP alternatives memory: 32K
> > [    0.940471] TSC deadline timer enabled
>
> So here is the first one which sets 'once'. Of course if you clear 'once'
> afterwards then this triggers because the context is completely
> different.
>
> So the right thing to do is to move this out of __setup_APIC_LVTT() and
> be done with it.

Thanks a lot.