Re: [PATCH dwarves v3 7/8] dwarf_loader: multithreading with a job/worker model

[Arnaldo Carvalho de Melo <acme@kernel.org>]

On Mon, Dec 30, 2024 at 01:11:41PM -0300, Arnaldo Carvalho de Melo wrote:
> > Not really :-\
> > 
> > root@number:/home/acme/git/pahole# pfunct --decl_info -F dwarf evtchn_fifo_is_pending /lib/modules/6.13.0-rc2/build/vmlinux
> > /* Used at: /home/acme/git/linux/drivers/xen/events/events_fifo.c */
> > /* <946502e> /home/acme/git/linux/drivers/xen/events/events_fifo.c:206 */
> > bool evtchn_fifo_is_pending(evtchn_port_t port);
> > /* Used at: /home/acme/git/linux/drivers/xen/events/events_fifo.c */
> > /* <946502e> /home/acme/git/linux/drivers/xen/events/events_fifo.c:206 */
> > bool evtchn_fifo_is_pending(evtchn_port_t port);
> > root@number:/home/acme/git/pahole#
> > 
> > So far I couldn't find an explanation for this oddity... Lets see if
> > after applying all patches we get past this.
 
> Its not related to this patch series, before we get two outputs for
> these (and other functions in
> /home/acme/git/linux/drivers/xen/events/events_fifo.c).
> 
> Still investigating.

root@number:/home/acme/git/pahole# perf probe -x ~/bin/pfunct function__show
Added new event:
  probe_pfunct:function_show (on function__show in /home/acme/git/pahole/build/pfunct)

You can now use it in all perf tools, such as:

	perf record -e probe_pfunct:function_show -aR sleep 1

root@number:/home/acme/git/pahole# perf trace -e probe_pfunct:function_show --call-graph dwarf pfunct --decl_info -F dwarf evtchn_fifo_set_pending /lib/modules/6.13.0-rc2/build/vmlinux
/* Used at: /home/acme/git/linux/drivers/xen/events/events_fifo.c */
/* <946517a> /home/acme/git/linux/drivers/xen/events/events_fifo.c:200 */
void evtchn_fifo_set_pending(evtchn_port_t port);
/* Used at: /home/acme/git/linux/drivers/xen/events/events_fifo.c */
/* <946517a> /home/acme/git/linux/drivers/xen/events/events_fifo.c:200 */
void evtchn_fifo_set_pending(evtchn_port_t port);
     0.000 pfunct/2006089 probe_pfunct:function_show(__probe_ip: 4208235)
                                       function__show (/home/acme/git/pahole/build/pfunct)
                                       pfunct_stealer (/home/acme/git/pahole/build/pfunct)
                                       cus__steal_now (/home/acme/git/pahole/build/libdwarves.so.1.0.0)
                                       dwarf_loader__worker_thread (/home/acme/git/pahole/build/libdwarves.so.1.0.0)
                                       start_thread (/usr/lib64/libc.so.6)
                                       clone3 (/usr/lib64/libc.so.6)
     0.134 pfunct/2006088 probe_pfunct:function_show(__probe_ip: 4208235)
                                       function__show (/home/acme/git/pahole/build/pfunct)
                                       cu_function_iterator (/home/acme/git/pahole/build/pfunct)
                                       cus__for_each_cu (/home/acme/git/pahole/build/libdwarves.so.1.0.0)
                                       main (/home/acme/git/pahole/build/pfunct)
                                       __libc_start_call_main (/usr/lib64/libc.so.6)
                                       __libc_start_main@@GLIBC_2.34 (/usr/lib64/libc.so.6)
                                       _start (/home/acme/git/pahole/build/pfunct)
root@number:/home/acme/git/pahole#

With the following patch we get just one output for this case, but that
isn't the right solution... I'll look on removing the
cu_function_iterator() based printing, otherwise when printing all
matches we'll still duplicate the printings.

Anyway, doesn't seem related to the problem that tests/tests was
catching, that I'm not being able to reproduce anymore after having the
whole series applied, probably some race?

- Arnaldo

diff --git a/pfunct.c b/pfunct.c
index 55eafe8a8e790dcb..9645b004381a7e1e 100644
--- a/pfunct.c
+++ b/pfunct.c
@@ -518,7 +518,13 @@ static enum load_steal_kind pfunct_stealer(struct cu *cu,
 
 		if (tag) {
 			function__show(tag__function(tag), cu);
-			return show_all_matches ? LSK__DELETE : LSK__STOP_LOADING;
+			if (!show_all_matches) {
+				// Expedite exit, since we already did what was requested:
+				// print the first occurrence of a given function
+				exit(0);
+			}
+
+			return LSK__DELETE;
 		}
 	} else if (class_name) {
 		cu_class_iterator(cu, class_name);