linux-kernel - Re: [PATCH] rcu: do not include rtmutex

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Message-Id: <20171018204259.GR3521@linux.vnet.ibm.com>
Date:   Wed, 18 Oct 2017 13:42:59 -0700
From:   "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To:     Sebastian Andrzej Siewior <bigeasy@...utronix.de>
Cc:     kbuild test robot <fengguang.wu@...el.com>, kbuild-all@...org,
        Josh Triplett <josh@...htriplett.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
        Lai Jiangshan <jiangshanlai@...il.com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] rcu: do not include rtmutex_common.h unconditionally

On Wed, Oct 18, 2017 at 06:16:21PM +0200, Sebastian Andrzej Siewior wrote:
> On 2017-10-18 08:39:46 [-0700], Paul E. McKenney wrote:
> > Thank you very much, hand-applied as a preparatory patch for
> > "Suppress lockdep false-positive ->boost_mtx complaints", please see
> > below.
> okay.
> 
> > What I don't understand is why 0day test robot didn't complain about
> > my copy of the exact same patch.  Or maybe it did and I fat-fingered it?
> > Except that I have gotten "BUILD SUCCESS" reports for commits including
> > that one.
> 
> I don't know. It is a "defconfig" for m32r. Unless it skipped that one,
> dunno.

No idea here, either.

> > commit a06f537e75ea0a9e81245ede1b97bb3a5762b81b
> > Author: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
> > Date:   Wed Oct 18 08:33:44 2017 -0700
> > 
> >     rcu: do not include rtmutex_common.h unconditionally
> >     
> >     This commit adjusts include files and provides definitions in preparation
> >     for suppressing lockdep false-positive ->boost_mtx complaints.  Without
> >     this preparation, architectures not supporting rt_mutex will get build
> >     failures.
> >     
> >     Reported-by: kbuild test robot <fengguang.wu@...el.com>
> >     Signed-off-by: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
> >     Signed-off-by: Paul E. McKenney <paulmck@...ux.vnet.ibm.com>
> > 
> > diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h
> > index fed95fa941e6..969eae45f05d 100644
> > --- a/kernel/rcu/tree_plugin.h
> > +++ b/kernel/rcu/tree_plugin.h
> > @@ -54,6 +54,7 @@ DEFINE_PER_CPU(char, rcu_cpu_has_work);
> >   * This probably needs to be excluded from -rt builds.
> >   */
> >  #define rt_mutex_owner(a) ({ WARN_ON_ONCE(1); NULL; })
> > +#define rt_mutex_futex_unlock(x) WARN_ON_ONCE(1)
> >  
> >  #endif /* #else #ifdef CONFIG_RCU_BOOST */
> >  
> > @@ -911,8 +912,6 @@ void exit_rcu(void)
> >  
> >  #ifdef CONFIG_RCU_BOOST
> >  
> > -#include "../locking/rtmutex_common.h"
> > -
> >  static void rcu_wake_cond(struct task_struct *t, int status)
> >  {
> >  	/*
> 
> So this probably works. This is
>   https://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu.git/commit/?h=rcu%2Fdev&id=a06f537e75ea0a9e81245ede1b97bb3a5762b81b&context=40&ignorews=0&dt=0
> 
> and the rtmutex_common is still in the ifdef which confused me at first.
> But then you wrote "preparatory" and I saw the following patch
>   https://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu.git/commit/?h=rcu/next&id=33d7471ce21202ce954993552c2e0298d9e0f031
> 
> where you move that include rtmutex_common.h. You shouldn't do that
> because "rt_mutex_futex_unlock()" has been added added here for the
> !BOOST + TREE case. So I thing this should break your build if you
> disable CONFIG_FUTEX (which in turn unselects CONFIg_RT_MUTEX).

Builds for me on x86 and 0day test robot hasn't complained, but might
as well get it right.  The new commits are:

a06f537e75ea ("rcu: do not include rtmutex_common.h unconditionally")
4a0fb5d70bb2 ("rcu: Suppress lockdep false-positive ->boost_mtx complaints")

							Thanx, Paul