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Date:   Thu, 17 Jun 2021 18:58:23 +0100
From:   Will Deacon <will@kernel.org>
To:     Pavel Tatashin <pasha.tatashin@soleen.com>
Cc:     Huang Shijie <shijie@os.amperecomputing.com>,
        Catalin Marinas <catalin.marinas@arm.com>, tabba@google.com,
        Ard Biesheuvel <ardb@kernel.org>,
        Mark Rutland <mark.rutland@arm.com>,
        Linux ARM <linux-arm-kernel@lists.infradead.org>,
        LKML <linux-kernel@vger.kernel.org>, patches@amperecomputing.com,
        zwang@amperecomputing.com
Subject: Re: [PATCH] arm64: kexec: flush log to console in nmi_panic()
Message-ID: <20210617175822.GG24813@willie-the-truck>
References: <20210617125023.7288-1-shijie@os.amperecomputing.com>
 <20210617175211.GE24813@willie-the-truck>
 <CA+CK2bC5XW_AjnieWZ-ro8iqr0Jb7cz5Ss5549tJTq3Zm4GYiQ@mail.gmail.com>
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On Thu, Jun 17, 2021 at 01:55:08PM -0400, Pavel Tatashin wrote:
> On Thu, Jun 17, 2021 at 1:52 PM Will Deacon <will@kernel.org> wrote:
> >
> > On Thu, Jun 17, 2021 at 12:50:23PM +0000, Huang Shijie wrote:
> > > If kdump is configured, nmi_panic() may run to machine_kexec().
> > >
> > > But in NMI context, the log is put in PER-CPU nmi_print_seq.
> > > So we can not see any log on the console since we entered the NMI context,
> > > such as the "Bye!" in previous line.
> > >
> > > This patch fixes this issue by two steps:
> > >       1) Uses printk_safe_flush_on_panic() to flush the log from
> > >              nmi_print_seq to global printk ring buffer,
> > >         2) Then uses console_flush_on_panic() to flush to console.
> > >
> > > After this patch, we can see the "Bye!" log in the panic console.
> >
> > Does it matter? I'd be more inclined to remove the print altogether...
> 
> I agree, the print could be removed entirely. But, my assumption was
> that this patch meant to flush other buffered prints beside this last
> "Bye" one.

That sounds like something which should be done in the core code, rather
than the in the architecture backend (and looks like panic() might do this
already?)

Will