On Fri, Jul 27, 2018 at 12:26:59PM -0400, Steven Rostedt wrote:
> On Thu, 26 Jul 2018 16:50:43 -0700
> Joel Fernandes <j...@joelfernandes.org> wrote:
>
> > F
> > include/linux/tracepoint.h | 41 ++++++++++++++++++++++++++++++--------
> > kernel/tracepoint.c | 16 ++++++++++++++-
> > 2 files changed, 48 insertions(+), 9 deletions(-)
> >
> > diff --git a/include/linux/tracepoint.h b/include/linux/tracepoint.h
> > index 19a690b559ca..6e7bc6ebfcd8 100644
> > --- a/include/linux/tracepoint.h
> > +++ b/include/linux/tracepoint.h
> > @@ -15,6 +15,7 @@
> > */
> >
> > #include <linux/smp.h>
> > +#include <linux/srcu.h>
> > #include <linux/errno.h>
> > #include <linux/types.h>
> > #include <linux/cpumask.h>
> > @@ -33,6 +34,8 @@ struct trace_eval_map {
> >
> > #define TRACEPOINT_DEFAULT_PRIO 10
> >
> > +extern struct srcu_struct tracepoint_srcu;
> > +
> > extern int
> > tracepoint_probe_register(struct tracepoint *tp, void *probe, void *data);
> > extern int
> > @@ -75,10 +78,16 @@ int unregister_tracepoint_module_notifier(struct
> > notifier_block *nb)
> > * probe unregistration and the end of module exit to make sure there is no
> > * caller executing a probe when it is freed.
> > */
> > +#ifdef CONFIG_TRACEPOINTS
> > static inline void tracepoint_synchronize_unregister(void)
> > {
> > + synchronize_srcu(&tracepoint_srcu);
> > synchronize_sched();
> > }
> > +#else
> > +static inline void tracepoint_synchronize_unregister(void)
> > +{ }
> > +#endif
> >
> > #ifdef CONFIG_HAVE_SYSCALL_TRACEPOINTS
> > extern int syscall_regfunc(void);
> > @@ -129,18 +138,32 @@ extern void syscall_unregfunc(void);
> > * as "(void *, void)". The DECLARE_TRACE_NOARGS() will pass in just
> > * "void *data", where as the DECLARE_TRACE() will pass in "void *data,
> > proto".
> > */
> > -#define __DO_TRACE(tp, proto, args, cond, rcucheck)
> > \
> > +#define __DO_TRACE(tp, proto, args, cond, rcuidle) \
> > do { \
> > struct tracepoint_func *it_func_ptr; \
> > void *it_func; \
> > void *__data; \
> > + int __maybe_unused idx = 0; \
> > \
> > if (!(cond)) \
> > return; \
> > - if (rcucheck) \
> > - rcu_irq_enter_irqson(); \
> > - rcu_read_lock_sched_notrace(); \
> > - it_func_ptr = rcu_dereference_sched((tp)->funcs); \
> > + \
> > + /* srcu can't be used from NMI */ \
> > + if (rcuidle && in_nmi()) \
> > + WARN_ON_ONCE(1); \
>
> Why isn't the above:
>
> WARN_ON_ONCE(rcuidle && in_nmi());
>
> ?
>
> The rest looks fine.
When I refactored the code as Peter suggested I happen to move the warning
out but didn't simplify it further (I had it at the back of my head to do
that but missed it).
Since its quite a simple change I can send a follow up patch doing so later,
or can resend this one. What do you suggest?
thanks,
- Joel
