linux-kernel - Re: [PATCH] rcu: Reword help of RCU

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Date:   Thu, 6 Oct 2016 05:45:52 -0700
From:   "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To:     Nikolay Borisov <kernel@...p.com>
Cc:     linux-kernel@...r.kernel.org
Subject: Re: [PATCH] rcu: Reword help of RCU_TRACE option

On Wed, Oct 05, 2016 at 05:18:09PM +0300, Nikolay Borisov wrote:
> 
> 
> On 10/05/2016 05:03 PM, Paul E. McKenney wrote:
> > On Wed, Oct 05, 2016 at 10:06:21AM +0300, Nikolay Borisov wrote:
> >> Explicitly state that enabling RCU_TRACE enables more
> >> tracepoints and not just "additional tracing".
> >>
> >> Signed-off-by: Nikolay Borisov <kernel@...p.com>
> >> ---
> >>
> >> Hello Paul, 
> >>
> >> Following our latest conversation re. enabling RCU tracing
> >> I had to actually go and look into the code to see which 
> >> option enables the additional tracepoints. I wasn't sure
> >> while reading the help of TRACE_RCU. So here is a patch
> >> which explicitly states that this enables additional 
> >> tracepoints. 
> >>
> >> Apply it if you deem necessary it might be just me that 
> >> thinks the description is not verbose enough. 
> >>
> >>  lib/Kconfig.debug | 4 ++--
> >>  1 file changed, 2 insertions(+), 2 deletions(-)
> >>
> >> diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
> >> index cab7405f48d2..f8c3468ec7ef 100644
> >> --- a/lib/Kconfig.debug
> >> +++ b/lib/Kconfig.debug
> >> @@ -1429,8 +1429,8 @@ config RCU_TRACE
> >>  	depends on DEBUG_KERNEL
> >>  	select TRACE_CLOCK
> >>  	help
> >> -	  This option provides tracing in RCU which presents stats
> >> -	  in debugfs for debugging RCU implementation.
> >> +	  This option enables additional tracepoints in RCU which present
> >> +	  stats in debugfs for debugging RCU implementation.
> > 
> > How about something like this?
> > 
> > 	This option provides tracing in RCU which presents stats
> > 	in debugfs for debugging RCU implementation.  It also enables
> > 	additional tracepoints for ftrace-style event tracing.
> 
> So long as it's explicitly stated that it also enables tracepoints it's
> all fine by me. Apparently I'm not the only one who got confused. In a
> question re. CONFIG_RCU_TRACE here is what someone said on IRC:
> 
> "what's tracepoints do you mean? this option enables the additional
> statistics permanently."
> 
> Care to apply it with the revised wording or shall I resend?

Please see below for the current state.

							Thanx, Paul

------------------------------------------------------------------------

commit a30cd69bdcb1ae12cb243e75eddd608c1798d438
Author: Nikolay Borisov <kernel@...p.com>
Date:   Thu Oct 6 05:42:39 2016 -0700

    rcu: RCU_TRACE enables event tracing as well as debugfs
    
    The commit brings the RCU_TRACE Kconfig option's help text up to date
    by noting that it enables additional event tracing as well as debugfs.
    
    Signed-off-by: Nikolay Borisov <kernel@...p.com>
    [ paulmck:  Do some wordsmithing. ]
    Signed-off-by: Paul E. McKenney <paulmck@...ux.vnet.ibm.com>

diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index 2b5441812214..7f8e8f3c72ea 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -1450,7 +1450,8 @@ config RCU_TRACE
 	select TRACE_CLOCK
 	help
 	  This option provides tracing in RCU which presents stats
-	  in debugfs for debugging RCU implementation.
+	  in debugfs for debugging RCU implementation.  It also enables
+	  additional tracepoints for ftrace-style event tracing.
 
 	  Say Y here if you want to enable RCU tracing
 	  Say N if you are unsure.