Re: [PATCH -tip 1/2] Add "notrace" to RCU function headers used by ftrace.

Steven Rostedt
2009-08-25T02:11:44Z

On Mon, 24 Aug 2009, Paul E. McKenney wrote:

> On Mon, Aug 24, 2009 at 07:38:51PM -0400, Steven Rostedt wrote:
> >
> > On Mon, 24 Aug 2009, Paul E. McKenney wrote:
> >
> > > Both rcu_read_lock_sched_notrace() and rcu_read_unlock_sched_notrace()
> > > are used by ftrace, and thus need to be marked "notrace". Unfortunately,
> > > my naive assumption that gcc would see the inner "notrace" does not hold.
> > > Kudos to Lai Jiangshan for noting this.
> > >
> > > Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
> > > ---
> > > include/linux/rcupdate.h | 4 ++--
> > > 1 files changed, 2 insertions(+), 2 deletions(-)
> > >
> > > diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h
> > > index ec90fc3..8b4422c 100644
> > > --- a/include/linux/rcupdate.h
> > > +++ b/include/linux/rcupdate.h
> > > @@ -191,7 +191,7 @@ static inline void rcu_read_lock_sched(void)
> > > __acquire(RCU_SCHED);
> > > rcu_read_acquire();
> > > }
> > > -static inline void rcu_read_lock_sched_notrace(void)
> > > +static inline notrace void rcu_read_lock_sched_notrace(void)
> > > {
> > > preempt_disable_notrace();
> > > __acquire(RCU_SCHED);
> > > @@ -209,7 +209,7 @@ static inline void rcu_read_unlock_sched(void)
> > > __release(RCU_SCHED);
> > > preempt_enable();
> > > }
> > > -static inline void rcu_read_unlock_sched_notrace(void)
> > > +static inline notrace void rcu_read_unlock_sched_notrace(void)
> >
> > Funny, inlines should not be traced. Is gcc ignoring the inlines here?
>
> Well, that was my line of thinking as well, until Lai Jiangshan set
> me straight. Version 4.x of gcc apparently decides on a case-by-case
> basis.

Yeah, I've seen gcc do it, but when it does it to static inlines in header
files, I just get a feeling to squinge.

-- Steve