On Mon, 10 Apr 2017 11:29:01 -0700 "Paul E. McKenney" <paul...@linux.vnet.ibm.com> wrote:
> On Mon, Apr 10, 2017 at 02:10:12PM -0400, Steven Rostedt wrote: > > From: "Steven Rostedt (VMware)" <rost...@goodmis.org> > > > > Stack tracing discovered that there's a small location inside the RCU > > infrastructure where calling rcu_irq_enter() does not work. As trace events > > use rcu_irq_enter() it must make sure that it is functionable. A check > > against rcu_irq_enter_disabled() is added with a WARN_ON_ONCE() as no trace > > event should ever be used in that part of RCU. If the warning is triggered, > > then the trace event is ignored. > > > > Restructure the __DO_TRACE() a bit to get rid of the prercu and postrcu, > > and just have an rcucheck that does the work from within the _DO_TRACE() > > macro. gcc optimization will compile out the rcucheck=0 case. > > > > Link: http://lkml.kernel.org/r/20170405093207.404f8...@gandalf.local.home > > > > Acked-by: Mathieu Desnoyers <mathieu.desnoy...@efficios.com> > > Signed-off-by: Steven Rostedt (VMware) <rost...@goodmis.org> > > Acked-by: Paul E. McKenney <paul...@linux.vnet.ibm.com> > > As an aside, it looks like the rcu_irq_enter_disabled() settings > in the RCU idle-entry code could be placed under CONFIG_PROVE_RCU=y > should my idle-entry-overhead concerns prove to be well-founded. > The errors would be caught during testing, but no production-side > overhead. Even with the underscored __this_cpu_*() calls? > > Again, I am not necessarily agitating for this change now, just getting > this possibility on the record. ;-) That would be easy to add :-) But we can do that at a later time. -- Steve
