[Bug libdw/21174] New: libdw with perf: duplication of entries in callstack

[thommyj at gmail dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=21174
            Bug ID: 21174
           Summary: libdw with perf: duplication of entries in callstack
           Product: elfutils
           Version: unspecified
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: libdw
          Assignee: unassigned at sourceware dot org
          Reporter: thommyj at gmail dot com
                CC: elfutils-devel at sourceware dot org
  Target Milestone: ---

Hi,

running perf together with libdw for stack unwinding using dwarf on an
arm64 board. I'm a bit puzzled of the callstack that is unwinded.
Sometimes I get the same entry twice out from libdw

Normal sample:
23_HalInterrupt   462  1087.469883:    6802721 cpu-clock:
         6e3628 IBUFDIST_distribute (/usr/local/bin/Application)
         6f33bc endOfFrame (/usr/local/bin/Application)
         6f2fcc interrupt (/usr/local/bin/Application)
         6f8c9c interruptHandler (/usr/local/bin/Application)
         6f7130 taskFunction (/usr/local/bin/Application)
     7fae555df8 [unknown] (/lib/libpthread-2.19-2014.08.so)

Sample with duplicated entries
23_HalInterrupt   462  1028.701041:    6802721 cpu-clock:
         6e3628 IBUFDIST_distribute (/usr/local/bin/Application)
         6e3628 IBUFDIST_distribute (/usr/local/bin/Application)
         6f33bc endOfFrame (/usr/local/bin/Application)
         6f2fcc interrupt (/usr/local/bin/Application)
         6f8c9c interruptHandler (/usr/local/bin/Application)
         6f7130 taskFunction (/usr/local/bin/Application)
     7fae555df8 [unknown] (/lib/libpthread-2.19-2014.08.so)

Sometimes it is the same address for the duplicate entry, sometimes
its different addresses but same symbol name. Its not always the first
entry, but seems to be more likely on first.

Is this a known problem?

BR,
Thommy Jakobsson

#record
>>perf record -t 462 -F 147 -g --call-graph dwarf -o halinter2.perf sleep 30
#dump data
>>perf script -i halinter2.perf

linux 4.4
elfutils 0.163
aarch64-linux-gnu-gcc (crosstool-NG linaro-1.13.1-4.9-2014.09 - Linaro
GCC 4.9-2014.09) 4.9.2 20140904 (prerelease)
Copyright (C) 2014 Free Software Found

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