Messages in this thread Patch in this message | | | Date | Fri, 27 Apr 2018 10:05:17 -0700 | From | "Paul E. McKenney" <> | Subject | Re: [PATCH RFC] tracepoint: Introduce tracepoint callbacks executing with preempt on |
| |
On Fri, Apr 27, 2018 at 10:00:48AM -0700, Paul E. McKenney wrote: > On Fri, Apr 27, 2018 at 12:46:41PM -0400, Steven Rostedt wrote: > > On Fri, 27 Apr 2018 09:45:54 -0700 > > "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> wrote: > > > > > > > That shouldn't be needed. For the rcu_read_lock_sched case, there is a > > > > > preempt_disable which needs to be a notrace, but for the srcu one, > > > > > since we don't do that, I think it should be fine. > > > > > > > > Actually, I think I may agree here too. Because the _notrace is for > > > > function tracing, and it shouldn't affect it. If people don't want it > > > > traced, they could add those functions to the list in the notrace file. > > > > > > OK, feel free to ignore my notrace srcu_read_lock() patch, then. ;-) > > > > Of course I wasn't thinking about the lockdep tracepoints that Joel > > mentioned, which happens to be the reason for all this discussion in > > the first place :-) Now I think we do need it. (OK, I can keep > > changing my mind, can't I?). > > You can, but at some point I start applying heavy-duty hysteresis. ;-) > > So the current thought (as of your having sent the above email) is that > we need notrace versions of srcu_read_lock() and srcu_read_unlock(), > but not for __srcu_read_lock() and __srcu_read_unlock(), correct?
And Joel noted offline that I messed up srcu_read_unlock_notrace(), so here is an updated patch with that fixed.
Thanx, Paul
------------------------------------------------------------------------
diff --git a/include/linux/srcu.h b/include/linux/srcu.h index 91494d7e8e41..3e72a291c401 100644 --- a/include/linux/srcu.h +++ b/include/linux/srcu.h @@ -195,6 +195,16 @@ static inline int srcu_read_lock(struct srcu_struct *sp) __acquires(sp) return retval; } +/* Used by tracing, cannot be traced and cannot invoke lockdep. */ +static inline notrace int +srcu_read_lock_notrace(struct srcu_struct *sp) __acquires(sp) +{ + int retval; + + retval = __srcu_read_lock(sp); + return retval; +} + /** * srcu_read_unlock - unregister a old reader from an SRCU-protected structure. * @sp: srcu_struct in which to unregister the old reader. @@ -209,6 +219,13 @@ static inline void srcu_read_unlock(struct srcu_struct *sp, int idx) __srcu_read_unlock(sp, idx); } +/* Used by tracing, cannot be traced and cannot call lockdep. */ +static inline notrace void +srcu_read_unlock_notrace(struct srcu_struct *sp, int idx) __releases(sp) +{ + __srcu_read_unlock(sp, idx); +} + /** * smp_mb__after_srcu_read_unlock - ensure full ordering after srcu_read_unlock *
| |