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

Paul E. McKenney
2012-07-08T07:09:08Z

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