On Freitag, 16. Juni 2017 08:14:56 CEST Jan Kratochvil wrote: > On Mon, 15 May 2017 17:04:44 +0200, Milian Wolff wrote: > > commit 1982ad48fc82c284a5cc55697a012d3357e84d01 > Author: Milian Wolff <milian.wo...@kdab.com> > Date: Wed May 24 15:21:25 2017 +0900 > > > --- a/tools/perf/util/unwind-libdw.c > > +++ b/tools/perf/util/unwind-libdw.c > > @@ -168,12 +168,16 @@ frame_callback(Dwfl_Frame *state, void *arg) > > ... > > > + if (!isactivation) > > + --pc; > > + > > FYI I find it as a regression a bit: > > perf-4.11.4-200.fc25.x86_64 > 30c563 gdb_main (/usr/libexec/gdb) > fae48 main (/usr/libexec/gdb) > 0x000055555564ee43 <+51>: callq 0x55555585f340 > <gdb_main(captured_main_args*)> 0x000055555564ee48 <+56>: mov > 0x18(%rsp),%rcx > > perf-4.12.0-0.rc5.git0.1.fc27.x86_64 > 39e32e gdb_main (/usr/libexec/gdb) > 10b6fa main (/usr/libexec/gdb) > 0x000055555565f6f6 <+54>: callq 0x5555558f17a0 > <gdb_main(captured_main_args*)> 0x000055555565f6fb <+59>: mov > 0x18(%rsp),%rcx > > In backtraces it is correct to show the source line of the calling line - as > perf does now after your fix - but one still should report PC address of > the start of the next instruction. At least this is what debuggers are > used to do: > > #9 gdb_main (args=0x7fffffffe2e0) at ../../gdb/main.c:1257 > #10 0x000055555565f6fb in main (argc=<optimized out>, argv=<optimized out>) > at ../../gdb/gdb.c:40 0x000055555565f6f6 <+54>: callq 0x5555558f17a0 > <gdb_main(captured_main_args*)> => 0x000055555565f6fb <+59>: mov > 0x18(%rsp),%rcx > Line 40 of "../../gdb/gdb.c" starts at address 0x55555565f6f6 <main(int, > char**)+54> and ends at 0x55555565f6fb <main(int, char**)+59>. Line 41 of > "../../gdb/gdb.c" starts at address 0x55555565f6fb <main(int, char**)+59> > and ends at 0x55555565f715. > > You see "gdb.c:40" and 0x000055555565f6fb in the backtrace despite > 0x55555565f6fb is already line 41. > > This is also why elfutils reports separately PC and 'isactivation' flag. > Instead of just reporting decreased PC.
Excuse me, but I'm having trouble following you. The non-GDB backtraces you are pasting do not show srcline information. So what exactly is broken? Can you show me the differences a bit more clearly? Maybe paste the perf output you get now and highlight what you'd expect instead? Best would be an accompanying test case that I can use to improve the situation, if possible? Thanks -- Milian Wolff | milian.wo...@kdab.com | Senior Software Engineer KDAB (Deutschland) GmbH&Co KG, a KDAB Group company Tel: +49-30-521325470 KDAB - The Qt Experts
