linux-kernel - Re: [PATCH] arm64: kexec: flush log to console in nmi

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Message-ID: <20210617175211.GE24813@willie-the-truck>
Date:   Thu, 17 Jun 2021 18:52:11 +0100
From:   Will Deacon <will@...nel.org>
To:     Huang Shijie <shijie@...amperecomputing.com>
Cc:     catalin.marinas@....com, tabba@...gle.com, ardb@...nel.org,
        mark.rutland@....com, pasha.tatashin@...een.com,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        patches@...erecomputing.com, zwang@...erecomputing.com
Subject: Re: [PATCH] arm64: kexec: flush log to console in nmi_panic()

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...

Will