linux-kernel - Re: [PATCH tip/core/rcu 20/21] checkpatch: Add warnings for {smp_,}read_barrier

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Message-Id: <20171204190646.GD7829@linux.vnet.ibm.com>
Date:   Mon, 4 Dec 2017 11:06:46 -0800
From:   "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To:     Joe Perches <joe@...ches.com>
Cc:     linux-kernel@...r.kernel.org, mingo@...nel.org,
        jiangshanlai@...il.com, dipankar@...ibm.com,
        akpm@...ux-foundation.org, mathieu.desnoyers@...icios.com,
        josh@...htriplett.org, tglx@...utronix.de, peterz@...radead.org,
        rostedt@...dmis.org, dhowells@...hat.com, edumazet@...gle.com,
        fweisbec@...il.com, oleg@...hat.com,
        Andy Whitcroft <apw@...onical.com>
Subject: Re: [PATCH tip/core/rcu 20/21] checkpatch: Add warnings for
 {smp_,}read_barrier_depends()

On Fri, Dec 01, 2017 at 08:45:13PM -0800, Joe Perches wrote:
> On Fri, 2017-12-01 at 13:44 -0800, Paul E. McKenney wrote:

[ . . . ]

> > Good points!  Like this?
> []
> > commit ff155ce179aab891dbe2ca80f82a453383fd165a
> > Author: Paul E. McKenney <paulmck@...ux.vnet.ibm.com>
> > Date:   Mon Nov 27 09:37:35 2017 -0800
> > 
> >     checkpatch: Add warnings for {smp_,}read_barrier_depends()
> >     
> >     Now that both smp_read_barrier_depends() and read_barrier_depends()
> >     are being de-emphasized, warn if any are added.
> >     
> >     Signed-off-by: Paul E. McKenney <paulmck@...ux.vnet.ibm.com>
> >     Cc: Andy Whitcroft <apw@...onical.com>
> >     Cc: Joe Perches <joe@...ches.com>
> >     [ paulmck: Skipped checking files and handled whitespace per Joe Perches. ]
> > 
> > diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
> []
> > @@ -5586,6 +5586,12 @@ sub process {
> >  			}
> >  		}
> >  
> > +# check for smp_read_barrier_depends and read_barrier_depends
> > +		if (!$file && $line =~ /\b(smp_|)read_barrier_depends\s*\(/) {
> > +			WARN("READ_BARRIER_DEPENDS",
> > +			     "Dependency barriers should only be used in READ_ONCE or DEC Alpha code" . $herecurr);
> 
> Almost right.  Missing a '\n' after "DEC Alpha code".
> Without the '\n', running checkpatch with --terse outputs badly.
> 
> If you really wanted to optimize, you could make the first (smp_|)
> become (?:smp_|) to avoid the unused capture group.
> Or perhaps this could emit the actual type in the message like:
> 
> 		if (!$file && $line =~ /\b((?:smp_|)read_barrier_depends)\s*\(/ {
> 			WARN("READ_BARRIER_DEPENDS",
> 			     "$1 should only be used in READ_ONCE or DEC Alpha code\n" . $herecurr);

How about like this?  (s/$1/$1read_barrier_depends/).

							Thanx, Paul

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

commit e4f1d781e33c150547c68e55099794b98ee14d5e
Author: Paul E. McKenney <paulmck@...ux.vnet.ibm.com>
Date:   Mon Nov 27 09:37:35 2017 -0800

    checkpatch: Add warnings for {smp_,}read_barrier_depends()
    
    Now that both smp_read_barrier_depends() and read_barrier_depends()
    are being de-emphasized, warn if any are added.
    
    Signed-off-by: Paul E. McKenney <paulmck@...ux.vnet.ibm.com>
    Cc: Andy Whitcroft <apw@...onical.com>
    Cc: Joe Perches <joe@...ches.com>
    [ paulmck: Skipped checking files and handled whitespace per Joe Perches. ]

diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
index 95cda3ecc66b..9a384bfe2bd5 100755
--- a/scripts/checkpatch.pl
+++ b/scripts/checkpatch.pl
@@ -5586,6 +5586,12 @@ sub process {
 			}
 		}
 
+# check for smp_read_barrier_depends and read_barrier_depends
+		if (!$file && $line =~ /\b(smp_|)read_barrier_depends\s*\(/) {
+			WARN("READ_BARRIER_DEPENDS",
+			     "$1read_barrier_depends should only be used in READ_ONCE or DEC Alpha code\n" . $herecurr);
+		}
+
 # check of hardware specific defines
 		if ($line =~ m@^.\s*\#\s*if.*\b(__i386__|__powerpc64__|__sun__|__s390x__)\b@ && $realfile !~ m@...lude/asm-@) {
 			CHK("ARCH_DEFINES",