linux-kernel - Re: [PATCH v2 10/15] dyndbg: add open and close commands for trace

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Date: Wed, 10 Jan 2024 13:40:38 +0100
From: Łukasz Bartosik <lb@...ihalf.com>
To: jim.cromie@...il.com, Jason Baron <jbaron@...mai.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>, Kees Cook <keescook@...omium.org>, 
	Douglas Anderson <dianders@...omium.org>, Guenter Roeck <groeck@...gle.com>, 
	Yaniv Tzoreff <yanivt@...gle.com>, Benson Leung <bleung@...gle.com>, 
	Steven Rostedt <rostedt@...dmis.org>, Vincent Whitchurch <vincent.whitchurch@...s.com>, 
	Pekka Paalanen <ppaalanen@...il.com>, Sean Paul <seanpaul@...omium.org>, 
	Daniel Vetter <daniel@...ll.ch>, linux-kernel@...r.kernel.org, upstream@...ihalf.com
Subject: Re: [PATCH v2 10/15] dyndbg: add open and close commands for trace

wt., 9 sty 2024 o 16:20 <jim.cromie@...il.com> napisał(a):
>
> On Fri, Jan 5, 2024 at 3:46 PM Jason Baron <jbaron@...mai.com> wrote:
> >
> > On 11/30/23 6:40 PM, Łukasz Bartosik wrote:
> > > Add open and close commands for opening and closing trace instances.
> > > The open command has to be mandatory followed by a trace instance name.
> > > If a trace instance already exists in <debugfs>/tracing/instances
> > > directory then the open command will reuse it otherwise a new trace
> > > instance with a name provided to the open will be created. Close
> > > command closes previously opened trace instance. The close will
> > > fail if a user tries to close non-existent trace instances or an
> > > instance which was not previously opened.
> > >
> > > For example the following command will open (create or reuse existing)
> > > trace instance located in <debugfs>/tracing/instances/usbcore:
> > >
> > >      echo "open usbcore" > <debugfs>/dynamic_debug/control
> >
> > Hi,
> >
> > I'm wondering why this needs to be part of dynamic debug? Can't we make
> > trace instances via 'mkdir' and then use those from the dynamic debug side?
> >
>
> I believe thats what happens now -
>
> open foo on already opened foo is not an error.
> so if the instance is already created, it just gets used, without
> clearing the buffer.

Yes, I confirm this behavior.

> So it can integrate with externally admin'd tracebufs.
>
> the open foo requirement means that we can validate foo,
> and error properly if it is mis-spelled
>
>
>
> > Thanks,
> >
> > -Jason
> >
> >