On Wed, 2 Dec 2015 15:36:50 -0800 Dave Hansen <dave.hansen@xxxxxxxxx> wrote: > On 12/02/2015 02:53 PM, Yang Shi wrote: > > diff --git a/mm/gup.c b/mm/gup.c > > index deafa2c..10245a4 100644 > > --- a/mm/gup.c > > +++ b/mm/gup.c > > @@ -13,6 +13,9 @@ > > #include <linux/rwsem.h> > > #include <linux/hugetlb.h> > > > > +#define CREATE_TRACE_POINTS > > +#include <trace/events/gup.h> > > + > > #include <asm/pgtable.h> > > #include <asm/tlbflush.h> > > This needs to be _the_ last thing that gets #included. Otherwise, you > risk colliding with any other trace header that gets implicitly included > below. Agreed. > > > @@ -1340,6 +1346,8 @@ int __get_user_pages_fast(unsigned long start, int nr_pages, int write, > > start, len))) > > return 0; > > > > + trace_gup_get_user_pages_fast(start, nr_pages, write, pages); > > + > > /* > > * Disable interrupts. We use the nested form as we can already have > > * interrupts disabled by get_futex_key. > > It would be _really_ nice to be able to see return values from the > various gup calls as well. Is that feasible? Only if you rewrite the functions to have a single return code path that we can add a tracepoint too. Or have a wrapper function that gets called directly that calls these functions internally and the tracepoint can trap the return value. I can probably make function_graph tracer give return values, although it will give a return value for void functions as well. And it may give long long returns for int returns that may have bogus data in the higher bits. -- Steve -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>