Re: Wrong Perf Backtraces

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Please confirm my thought in the previous email, if it is correct.
On 2020-03-30 23:35, ahmadkhorrami wrote:

Sorry, I did not pay attention to the fact that we need debug info to be able to decode the callchain. So, without complete debug info the backtrace (either the symbols or the addresses) is bogus. But you say that the backtrace portions containing binaries with full debug info are OK. Am I right? Please confirm if this is the case.
If so, these portions may be enough for my current usecase.

On 2020-03-30 18:19, ahmadkhorrami wrote:

thanks, but I still do not understand the cause of the problem. It seems that it is purely a software bug and the callchain addresses seem wrong,by themselves. Am I right?
On 2020-03-30 17:37, Jiri Olsa wrote:

On Mon, Mar 30, 2020 at 08:09:53AM +0200, Milian Wolff wrote: On Sonntag, 29. März 2020 21:20:10 CEST Jiri Olsa wrote: On Sun, Mar 29, 2020 at 03:50:57PM +0200, Milian Wolff wrote: On Sonntag, 29. März 2020 14:39:33 CEST ahmadkhorrami wrote: Thanks. I did both of your changes. Perhaps some outputs are revised.
But I still have repeated function calls and the script detects them.
Here is one of them when the sampling period is 1000 events: <snip>

Here, we have two consecutive "7f91788120b5
(/usr/lib/x86_64-linux-gnu/ gtkwidget.c:0" lines,
while "gtk_widget_propagate_state+0x195" is not recursive. It should
call "gtk_container_forall", which does not occur even after the second
(inner) call.
Potentially you are just lacking some debug symbols here for this GTK
library. note that "gtkwidget.c:0" is bogus already - the line numbers
start with 1, so could we just skip those then? pass on all zero lined inlines
and not add/display them
I guess so - but quite frankly I'm a bit uneasy to do this without further exploration about the actual causes here. Afaik DWARF does not say anything about the validity, so in theory there might be some language/compiler that
encodes valid DWARF locations with line 0?

Generally, it would be quite interesting to figure out why there is /some/ DWARF data here such that the code thinks it's able to decode the inline frame
but then fails and leads to this confusing result?
right, but it's beyond my DWARF expertise ;-) we'll need
to wait till one of you guys could take a look on it


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