On Wed, 2 Dec 2015 15:36:50 -0800 Dave Hansen dave.hansen@intel.com 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