Re: [rcu:fixes.2012.07.06a 12/19] undefined reference to `rcu_is_cpu_idle'

["Paul E. McKenney" <paulmck@linux.vnet.ibm.com>]

On Sun, Jul 08, 2012 at 08:57:07AM +0800, Fengguang Wu wrote:
> On Sat, Jul 07, 2012 at 02:54:42PM -0700, Paul E. McKenney wrote:
> > On Sun, Jul 08, 2012 at 01:18:03AM +0800, wfg@linux.intel.com wrote:
> > > Hi Paul,
> > > 
> > > Kernel build failed on
> > > 
> > > tree:   git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu.git fixes.2012.07.06a
> > > head:   cfca927972e31a5b3da49bf641c525732ff3c357
> > > commit: 62fde6edf12b60fddb13a3f0a779c8be0bb7447e [12/19] rcu: Make __call_rcu() handle invocation from idle
> > > config: x86_64-randconfig-tip4 (attached as .config)
> > > 
> > > 
> > > kernel/built-in.o: In function `rcu_read_lock_bh_held': (.text+0x167d1): undefined reference to `rcu_is_cpu_idle'
> > > kernel/built-in.o: In function `lockdep_rcu_suspicious': (.text+0x367e8): undefined reference to `rcu_is_cpu_idle'
> > > kernel/built-in.o: In function `lockdep_rcu_suspicious': (.text+0x36815): undefined reference to `rcu_is_cpu_idle'
> > > kernel/built-in.o: In function `css_get_next': (.text+0x40f5a): undefined reference to `rcu_is_cpu_idle'
> > > drivers/built-in.o: In function `dst_link_failure': isdn_net.c:(.text+0x13950a): undefined reference to `rcu_is_cpu_idle'
> > > net/built-in.o:sock.c:(.text+0x3cec): more undefined references to `rcu_is_cpu_idle' follow
> > > 
> > > There are more similar errors in the other randconfigs.
> > 
> > Hmmm...  So you are building TINY_RCU without CONFIG_DEBUG_LOCK_ALLOC,
> > but with some checking enabled.  I -thought- I was testing that...
> > 
> > But, wait.  You do have CONFIG_DEBUG_LOCK_ALLOC defined.  That really
> > should cause rcu_is_cpu_idle() to be compiled into kernel/rcupdate.o.
> > And your config builds on my system with no errors.
> 
> I can reproduce the errors in a clean build. And I find the root cause to be
> the below line in rcutiny.c:
> 
> =>     #ifdef CONFIG_PROVE_RCU
> 
>         /*
>          * Test whether RCU thinks that the current CPU is idle.
>          */
>         int rcu_is_cpu_idle(void)

Ah!  Fixed by d7118175 in -next, -tip, and -rcu.  The bug was introduced
by 9b2e4f1880 in v3.3, but apparently the commit you found was the one
that actually exposed the bug.

What error were you bisecting for?

> > Was there perhaps another problem, maybe running out of disk space?
> 
> Sometimes it does run out of *memory*, because I aggressively put all
> .o files in tmpfs ;)  In which case the make/gcc tasks are killed and
> the abnormal situation is detected by grepping for "Terminated" lines
> in the build log.

Fair enough!  ;-)

							Thanx, Paul