Subject: Re: mmotm 2014-04-24-13-07 uploaded

From: "Paul E. McKenney" <[email-masked]>
Date: Mon, 28 Apr 2014 14:15:35 -0700

On Mon, Apr 28, 2014 at 01:32:38PM -0700, Randy Dunlap wrote:
> On 04/28/14 13:06, Paul E. McKenney wrote:
> > On Mon, Apr 28, 2014 at 07:21:27PM +0200, Richard Weinberger wrote:
> >> Am 28.04.2014 19:17, schrieb Randy Dunlap:
> >>>
> >>> uml defconfig on x86_64:
> >>>
> >>>   CC      arch/um/kernel/asm-offsets.s
> >>> In file included from include/linux/sem.h:5:0,
> >>>                  from include/linux/sched.h:35,
> >>>                  from arch/x86/um/shared/sysdep/kernel-offsets.h:2,
> >>>                  from arch/um/kernel/asm-offsets.c:1:
> >>> include/linux/rcupdate.h:257:20: error: static declaration of 'rcu_sysrq_start' follows non-static declaration
> >>> include/linux/rcupdate.h:250:6: note: previous declaration of 'rcu_sysrq_start' was here
> >>> include/linux/rcupdate.h:260:20: error: static declaration of 'rcu_sysrq_end' follows non-static declaration
> >>> include/linux/rcupdate.h:251:6: note: previous declaration of 'rcu_sysrq_end' was here
> >>> make[2]: *** [arch/um/kernel/asm-offsets.s] Error 1
> >>>
> >>>
> >>> Please test your patch(es).
> > 
> > Against exactly what?  ;-)
> 
> see $Subject

Testing my patches against MMOTM would be Stephen Rothwell's job.  ;-)

> >> Just in case, to build an x86_64 UML please run:
> >>
> >> make defconfig ARCH=um SUBARCH=x86_64
> >> make linux ARCH=um SUBARCH=x86_64
> > 
> > Hmmm....  Builds without errors in my local tree.
> > 
> > Make a clone of linux-next...
> > 
> > OK, now I get a different build failure:
> > 
> > /home/paulmck/public_git/linux-next/drivers/tty/sysrq.c:514: undefined reference to `rcu_sysrq_start'
> > /home/paulmck/public_git/linux-next/drivers/tty/sysrq.c:558: undefined reference to `rcu_sysrq_end'
> > 
> > This is due to Rik's "#include <linux/rcupdate.h>" getting lost somehow.
> > This #include is needed in drivers/tty/sysrq.c.
> > 
> > But maybe I need to be using some other branch of linux-next.  Am currently
> > on 5bd4e10b96ce20271688aa31d8bd739441249152, which is origin/master.  And
> > is also next-20140428.  If I should be somewhere else, please let me know.
> > 
> > OK, it also appears that my change to make TINY_RCU work is also missing,
> > possibly because Randy applied it by hand.
> 
> nope.
> 
> > Please see below for a patch against next-20140428 that makes this build
> > for me.  This is derived from Rik's patch, my patch, and is consistent with
> > Arnd's patch.
> > 
> > 							Thanx, Paul
> 
> Thnx, works for me.  Finally.

Good!

Rik, how would you like to proceed with this?

							Thanx, Paul

> > ------------------------------------------------------------------------
> > 
> > diff --git a/drivers/tty/sysrq.c b/drivers/tty/sysrq.c
> > index 6c3d11b..38d5f9a 100644
> > --- a/drivers/tty/sysrq.c
> > +++ b/drivers/tty/sysrq.c
> > @@ -46,6 +46,7 @@
> >  #include <linux/jiffies.h>
> >  #include <linux/syscalls.h>
> >  #include <linux/of.h>
> > +#include <linux/rcupdate.h>
> >  
> >  #include <asm/ptrace.h>
> >  #include <asm/irq_regs.h>
> > diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h
> > index e9cc71c..7b0a669 100644
> > --- a/include/linux/rcupdate.h
> > +++ b/include/linux/rcupdate.h
> > @@ -247,8 +247,17 @@ void rcu_idle_enter(void);
> >  void rcu_idle_exit(void);
> >  void rcu_irq_enter(void);
> >  void rcu_irq_exit(void);
> > +#ifdef CONFIG_RCU_STALL_COMMON
> >  void rcu_sysrq_start(void);
> >  void rcu_sysrq_end(void);
> > +#else /* #ifdef CONFIG_RCU_STALL_COMMON */
> > +static inline void rcu_sysrq_start(void)
> > +{
> > +}
> > +static inline void rcu_sysrq_end(void)
> > +{
> > +}
> > +#endif /* #else #ifdef CONFIG_RCU_STALL_COMMON */
> >  
> >  #ifdef CONFIG_RCU_USER_QS
> >  void rcu_user_enter(void);
> > diff --git a/kernel/rcu/update.c b/kernel/rcu/update.c
> > index 20caaf0..a2aeb4d 100644
> > --- a/kernel/rcu/update.c
> > +++ b/kernel/rcu/update.c
> > @@ -322,7 +322,8 @@ int rcu_jiffies_till_stall_check(void)
> >  
> >  void rcu_sysrq_start(void)
> >  {
> > -	rcu_cpu_stall_suppress = 2;
> > +	if (!rcu_cpu_stall_suppress)
> > +		rcu_cpu_stall_suppress = 2;
> >  }
> >  
> >  void rcu_sysrq_end(void)
> > 
> > --
> 
> 
> -- 
> ~Randy
>