linux-kernel - Re: [PATCH tip/core/rcu 02/20] torture: Prepare scripting for shift from %p to %pK

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Message-Id: <20171204161100.GT7829@linux.vnet.ibm.com>
Date:   Mon, 4 Dec 2017 08:11:00 -0800
From:   "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To:     David Laight <David.Laight@...LAB.COM>
Cc:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "mingo@...nel.org" <mingo@...nel.org>,
        "jiangshanlai@...il.com" <jiangshanlai@...il.com>,
        "dipankar@...ibm.com" <dipankar@...ibm.com>,
        "akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
        "mathieu.desnoyers@...icios.com" <mathieu.desnoyers@...icios.com>,
        "josh@...htriplett.org" <josh@...htriplett.org>,
        "tglx@...utronix.de" <tglx@...utronix.de>,
        "peterz@...radead.org" <peterz@...radead.org>,
        "rostedt@...dmis.org" <rostedt@...dmis.org>,
        "dhowells@...hat.com" <dhowells@...hat.com>,
        "edumazet@...gle.com" <edumazet@...gle.com>,
        "fweisbec@...il.com" <fweisbec@...il.com>,
        "oleg@...hat.com" <oleg@...hat.com>
Subject: Re: [PATCH tip/core/rcu 02/20] torture: Prepare scripting for shift
 from %p to %pK

On Mon, Dec 04, 2017 at 02:13:38PM +0000, David Laight wrote:
> From: Paul E. McKenney
> > Sent: 04 December 2017 13:42
> > On Mon, Dec 04, 2017 at 12:32:30PM +0000, David Laight wrote:
> > > From: Paul E. McKenney
> > > > Sent: 01 December 2017 20:09
> > > >
> > > > Because %p prints "(null)" and %pK prints "0000000000000000" or (on
> > > > 32-bit systems) "00000000", this commit adjusts torture-test scripting
> > > > accordingly.
> > >
> > > Surely NULL v not-NULL is one bit of info that the message needs to contain?
> > 
> > Indeed.  So the script needs to check for the strings "00000000",
> > "0000000000000000", and "(null) in the console output".  The "(null)"
> > is what "%p" prints for a NULL pointer, and the other two strings are
> > what "%pK" prints for a NULL pointer.
> > 
> > Or am I missing your point?
> 
> I was thinking that even %pK should print "(null)".

That was my expectation, as in the need for this patch came as a
surprise to me.

> Perhaps it should have printed a fixed, non-zero value for non-zero
> pointers.

I must leave this to the people who have a dog in that contest.  ;-)

							Thanx, Paul