Re: [PATCH 4.1 125/159] net: call rcu_read_lock early in process_backlog

Julian Anastasov
2015-09-29T19:22:04Z

Hello,

On Tue, 29 Sep 2015, Andre Tomt wrote:

> On 29. sep. 2015 10:39, Andre Tomt (LKML) wrote:
> > I just had another hang with it reverted on two different guests..
> > However it took nearly 6 hours rather than the usual "few minutes" for
> > these two. So now I'm a little unsure about my initial conclusions.
> >
> > On 29. sep. 2015 09:40, Julian Anastasov wrote:
> >> On Tue, 29 Sep 2015, Andre Tomt (LKML) wrote:
> <snip>
> >> They are 2 related patches, the first one is
> >> [PATCH 4.1 124/159] net: do not process device backlog during unregistration
> >
> > Would reverting this change anything outside device unregistration at all?

Its role is only during unregistration, so it
should not matter.

> I enabled CONFIG_RCU_CPU_STALL_INFO=y and disabled a bunch of non-virt
> drivers to speed up debugging. But no output this time either. Got any
> ideas on debugging options I've forgot? Useful sysrqs?

Checking my .config for debugs... I'm not expert
on this but may be such settings can help:

CONFIG_PROVE_RCU=y
CONFIG_PROVE_RCU_REPEATEDLY=y
CONFIG_SPARSE_RCU_POINTER=y
CONFIG_DEBUG_SPINLOCK=y
CONFIG_DEBUG_MUTEXES=y
CONFIG_DEBUG_LOCK_ALLOC=y
CONFIG_PROVE_LOCKING=y
CONFIG_LOCKDEP=y
CONFIG_DEBUG_ATOMIC_SLEEP=y
CONFIG_TRACE_IRQFLAGS=y
CONFIG_STACKTRACE=y - you have this one
CONFIG_DEBUG_BUGVERBOSE=y

Regards

--
Julian Anastasov <ja@ssi.bg>