linux-kernel - Re: [PATCH] RAS: Fix the trace_show() function to output trace

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Date:   Wed, 5 Oct 2022 20:17:07 +0200
From:   Borislav Petkov <bp@...en8.de>
To:     Tony Luck <tony.luck@...el.com>
Cc:     x86@...nel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] RAS: Fix the trace_show() function to output trace_count

On Wed, Oct 05, 2022 at 09:16:45AM -0700, Tony Luck wrote:
> The /sys/kernel/debug/ras/daemon_active is used to indicate to some
> kernel code whether there is a user mode consumer of RAS trace events
> to decide whether to print to the console.
> 
> The intent was that reading daemon_active would give the same indication
> to users. But the code is broken and does not display anything.

Huh, looking at that Fixes commit, it says:

"One can track which daemon opens it via "lsof
/path/to/debugfs/ras/daemon_active"."

# lsof /sys/kernel/debug/ras/daemon_active
COMMAND   PID USER   FD   TYPE DEVICE SIZE/OFF NODE NAME
tail    13339 root    3r   REG    0,6        0   27 /sys/kernel/debug/ras/daemon_active

So it works as advertized I'd say.

> Add a seq_printf() to output the current value of the trace_count.

Now, if you want to cat that file, that's a different story.

:-)

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette