linux-kernel - Re: [for-next][PATCH 7/7] tracing: Have stack trace not record if RCU is not watching

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Date:   Thu, 14 Dec 2017 20:47:35 -0500
From:   Steven Rostedt <rostedt@...dmis.org>
To:     "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
Cc:     linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [for-next][PATCH 7/7] tracing: Have stack trace not record if
 RCU is not watching

On Wed, 13 Dec 2017 20:34:34 -0800
"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com> wrote:

> On Wed, Dec 13, 2017 at 03:47:03PM -0500, Steven Rostedt wrote:
> > From: "Steven Rostedt (VMware)" <rostedt@...dmis.org>
> > 
> > The stack tracer records a stack dump whenever it sees a stack usage that is
> > more than what it ever saw before. This can happen at any function that is
> > being traced. If it happens when the CPU is going idle (or other strange
> > locations), RCU may not be watching, and in this case, the recording of the
> > stack trace will trigger a warning. There's been lots of efforts to make
> > hacks to allow stack tracing to proceed even if RCU is not watching, but
> > this only causes more issues to appear. Simply do not trace a stack if RCU
> > is not watching. It probably isn't a bad stack anyway.
> > 
> > Cc: "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
> > Signed-off-by: Steven Rostedt (VMware) <rostedt@...dmis.org>  
> 
> Acked-by: "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
>

Thanks!

-- Steve