On Thu, Jun 19, 2014 at 04:32:38PM -0400, Sasha Levin wrote: > On 06/19/2014 04:29 PM, Paul E. McKenney wrote: > > On Thu, Jun 19, 2014 at 09:29:08PM +0200, Thomas Gleixner wrote: > >> > On Thu, 19 Jun 2014, Paul E. McKenney wrote: > >> > > >>> > > On Thu, Jun 19, 2014 at 10:03:04AM -0500, Christoph Lameter wrote: > >>>> > > > On Thu, 19 Jun 2014, Sasha Levin wrote: > >>>> > > > > >>>>> > > > > [ 690.770137] ? __this_cpu_preempt_check (lib/smp_processor_id.c:63) > >>>>> > > > > [ 690.770137] __slab_alloc (mm/slub.c:1732 mm/slub.c:2205 mm/slub.c:2369) > >>>>> > > > > [ 690.770137] ? __lock_acquire (kernel/locking/lockdep.c:3189) > >>>>> > > > > [ 690.770137] ? __debug_object_init (lib/debugobjects.c:100 lib/debugobjects.c:312) > >>>>> > > > > [ 690.770137] kmem_cache_alloc (mm/slub.c:2442 mm/slub.c:2484 mm/slub.c:2489) > >>>>> > > > > [ 690.770137] ? __debug_object_init (lib/debugobjects.c:100 lib/debugobjects.c:312) > >>>>> > > > > [ 690.770137] ? debug_object_activate (lib/debugobjects.c:439) > >>>>> > > > > [ 690.770137] __debug_object_init (lib/debugobjects.c:100 lib/debugobjects.c:312) > >>>>> > > > > [ 690.770137] debug_object_init (lib/debugobjects.c:365) > >>>>> > > > > [ 690.770137] rcuhead_fixup_activate (kernel/rcu/update.c:231) > >>>>> > > > > [ 690.770137] debug_object_activate (lib/debugobjects.c:280 lib/debugobjects.c:439) > >>>>> > > > > [ 690.770137] ? discard_slab (mm/slub.c:1486) > >>>>> > > > > [ 690.770137] __call_rcu (kernel/rcu/rcu.h:76 (discriminator 2) kernel/rcu/tree.c:2585 (discriminator 2)) > >>>> > > > > >>>> > > > __call_rcu does a slab allocation? This means __call_rcu can no longer be > >>>> > > > used in slab allocators? What happened? > >>> > > > >>> > > My guess is that the root cause is a double call_rcu(), call_rcu_sched(), > >>> > > call_rcu_bh(), or call_srcu(). > >>> > > > >>> > > Perhaps the DEBUG_OBJECTS code now allocates memory to report errors? > >>> > > That would be unfortunate... > >> > > >> > Well, no. Look at the callchain: > >> > > >> > __call_rcu > >> > debug_object_activate > >> > rcuhead_fixup_activate > >> > debug_object_init > >> > kmem_cache_alloc > >> > > >> > So call rcu activates the object, but the object has no reference in > >> > the debug objects code so the fixup code is called which inits the > >> > object and allocates a reference .... > > OK, got it. And you are right, call_rcu() has done this for a very > > long time, so not sure what changed. > > It's probable my fault. I've introduced clone() and unshare() fuzzing. > > Those two are full with issues and I've been waiting with enabling those > until the rest of the kernel could survive trinity for more than an hour. Well, that might explain why I haven't seen it in my testing. ;-) Thanx, Paul -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>