On Mon, Oct 06, 2014 at 05:35:52PM -0400, Steven Rostedt wrote: > From: Dave Hansen <[email protected]> > > Dave Jones reported seeing a bug from one of my TLB tracepoints: > > http://lkml.kernel.org/r/[email protected] > > I've been running these patches for months and never saw this. > But, a big chunk of my testing, especially with all the debugging > enabled, was in a vm where intel_idle doesn't work. On the > systems where I was using intel_idle, I never had lockdep enabled > and this tracepoint on at the same time. > > This patch ensures that whenever we have lockdep available, we do > _some_ RCU activity at the site of the tracepoint, despite > whether the tracepoint's condition matches or even if the > tracepoint itself is completely disabled. This is a bit of a > hack, but it is pretty self-contained. > > I confirmed that with this patch plus lockdep I get the same > splat as Dave Jones did, but without enabling the tracepoint > explicitly. > > Link: http://lkml.kernel.org/p/[email protected] > > Signed-off-by: Dave Hansen <[email protected]> > Cc: Dave Hansen <[email protected]> > Cc: Dave Jones <[email protected]>, > Cc: [email protected]
Reviewed-by: Paul E. McKenney <[email protected]> > Cc: Ingo Molnar <[email protected]> > Signed-off-by: Steven Rostedt <[email protected]> > --- > include/linux/tracepoint.h | 11 +++++++++++ > 1 file changed, 11 insertions(+) > > diff --git a/include/linux/tracepoint.h b/include/linux/tracepoint.h > index b1293f15f592..e08e21e5f601 100644 > --- a/include/linux/tracepoint.h > +++ b/include/linux/tracepoint.h > @@ -157,6 +157,12 @@ extern void syscall_unregfunc(void); > * Make sure the alignment of the structure in the __tracepoints section will > * not add unwanted padding between the beginning of the section and the > * structure. Force alignment to the same alignment as the section start. > + * > + * When lockdep is enabled, we make sure to always do the RCU portions of > + * the tracepoint code, regardless of whether tracing is on or we match the > + * condition. This lets us find RCU issues triggered with tracepoints even > + * when this tracepoint is off. This code has no purpose other than poking > + * RCU a bit. > */ > #define __DECLARE_TRACE(name, proto, args, cond, data_proto, data_args) \ > extern struct tracepoint __tracepoint_##name; \ > @@ -167,6 +173,11 @@ extern void syscall_unregfunc(void); > TP_PROTO(data_proto), \ > TP_ARGS(data_args), \ > TP_CONDITION(cond),,); \ > + if (IS_ENABLED(CONFIG_LOCKDEP)) { \ > + rcu_read_lock_sched_notrace(); \ > + rcu_dereference_sched(__tracepoint_##name.funcs);\ > + rcu_read_unlock_sched_notrace(); \ > + } \ > } \ > __DECLARE_TRACE_RCU(name, PARAMS(proto), PARAMS(args), \ > PARAMS(cond), PARAMS(data_proto), PARAMS(data_args)) \ > -- > 2.0.1 > > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
