linux-kernel - Re: [PATCH net-next 5/7] netconsole: add task name to extra data fields

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Message-ID: <20250225141029.GV1615191@kernel.org>
Date: Tue, 25 Feb 2025 14:10:29 +0000
From: Simon Horman <horms@...nel.org>
To: Breno Leitao <leitao@...ian.org>
Cc: Andrew Lunn <andrew+netdev@...n.ch>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	Jonathan Corbet <corbet@....net>, Shuah Khan <shuah@...nel.org>,
	netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-doc@...r.kernel.org, linux-kselftest@...r.kernel.org,
	kernel-team@...a.com
Subject: Re: [PATCH net-next 5/7] netconsole: add task name to extra data
 fields

On Tue, Feb 25, 2025 at 03:17:33AM -0800, Breno Leitao wrote:
> Hello Simon,
> 
> On Tue, Feb 25, 2025 at 10:19:10AM +0000, Simon Horman wrote:
> > On Fri, Feb 21, 2025 at 05:52:10AM -0800, Breno Leitao wrote:
> > > This is the core patch for this whole patchset. Add support for
> > > including the current task's name in netconsole's extra data output.
> > > This adds a new append_taskname() function that writes the task name
> > > (from current->comm) into the target's extradata buffer, similar to how
> > > CPU numbers are handled.
> > > 
> > > The task name is included when the SYSDATA_TASKNAME field is set,
> > > appearing in the format "taskname=<name>" in the output. This additional
> > > context can help with debugging by showing which task generated each
> > > console message.
> > > 
> > > Signed-off-by: Breno Leitao <leitao@...ian.org>
> > > ---
> > >  drivers/net/netconsole.c | 14 +++++++++++++-
> > >  1 file changed, 13 insertions(+), 1 deletion(-)
> > > 
> > > diff --git a/drivers/net/netconsole.c b/drivers/net/netconsole.c
> > > index 5a29144ae37ee7b487b1a252b0f2ce8574f9cefa..625f4c0be11d8deb454139b1c526abc842697219 100644
> > > --- a/drivers/net/netconsole.c
> > > +++ b/drivers/net/netconsole.c
> > > @@ -1179,12 +1179,22 @@ static int append_cpu_nr(struct netconsole_target *nt, int offset)
> > >  			 raw_smp_processor_id());
> > >  }
> > >  
> > > +static int append_taskname(struct netconsole_target *nt, int offset)
> > > +{
> > > +	if (WARN_ON_ONCE(!current))
> > > +		return 0;
> > 
> > Hi Breno,
> > 
> > I gather that theoretically this could occur, but it isn't expected
> > to happen in practice. Is that right?
> 
> That's correct. `current` isn't expected to be NULL in practice.
> I've been running this code on several servers for days and have never
> encountered this warning. 
> 
> While the taskname feature isn't enabled during early boot, netconsole
> might be active at that time, which is why I exercised extra caution
> here.
> 
> If you also think this is safe, I am more than happy to remove this
> check.

Thanks for the clarification.

Given the above explanation I would have added the check too.
So from my PoV we are good.

Reviewed-by: Simon Horman <horms@...nel.org>