Messages in this thread | | | Date | Mon, 09 Dec 2013 07:05:15 -0700 | From | David Ahern <> | Subject | Re: [PATCH] perf tool: Ensure forward progress unwinding frames |
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On 12/9/13, 3:02 AM, Jiri Olsa wrote: >> On 12/1/13, 5:01 PM, David Ahern wrote: >>> The dwarf option for callstacks is getting stuck on the unwind and showing >>> repeated frames. For example, >>> >>> qemu-system-x86 13759 [001] 287663.084957: syscalls:sys_enter_futex: uaddr: 0x7f770a958700, op: 0x00000081, val: 0x00000001, utime: 0x7f75ea >>> 7f7705fd23ea __lll_unlock_wake (/lib64/libpthread-2.14.90.so) >>> 7f7705fcf045 _L_unlock_649 (/lib64/libpthread-2.14.90.so) >>> 7f7705fcf045 _L_unlock_649 (/lib64/libpthread-2.14.90.so) >>> 7f7705fcf045 _L_unlock_649 (/lib64/libpthread-2.14.90.so) >>> 7f7705fcf045 _L_unlock_649 (/lib64/libpthread-2.14.90.so) >>> 7f7705fcf045 _L_unlock_649 (/lib64/libpthread-2.14.90.so) >>> ... > > I wonder this is us or libunwind bug (or cfi code) ;-) > > looks like you can reproduce..? are you using the latest libunwind?
$ rpm -q libunwind libunwind-0.99-2.20110424git1e10c293.fc16.x86_64
> > >>> (Last frame repeats 126 times) >>> >>> Catch that the same frame is hit multiple times and break out of the loop. >>> >>> With this patch: >>> >>> qemu-system-x86 13759 [001] 287663.084967: syscalls:sys_exit_futex: 0x1 >>> 7f7705fd23ea __lll_unlock_wake (/lib64/libpthread-2.14.90.so) >>> 7f7705fcf045 _L_unlock_649 (/lib64/libpthread-2.14.90.so) >>> >>> Signed-off-by: David Ahern <dsahern@gmail.com> >>> Cc: Jiri Olsa <jolsa@redhat.com> >>> --- >>> tools/perf/util/unwind.c | 5 +++++ >>> 1 file changed, 5 insertions(+) >>> >>> diff --git a/tools/perf/util/unwind.c b/tools/perf/util/unwind.c >>> index 0efd5393de85..817ffc1f3a00 100644 >>> --- a/tools/perf/util/unwind.c >>> +++ b/tools/perf/util/unwind.c >>> @@ -563,6 +563,7 @@ static int get_entries(struct unwind_info *ui, unwind_entry_cb_t cb, >>> { >>> unw_addr_space_t addr_space; >>> unw_cursor_t c; >>> + unw_word_t prev_ip = 0; >>> int ret; >>> >>> addr_space = unw_create_addr_space(&accessors, 0); >>> @@ -579,6 +580,10 @@ static int get_entries(struct unwind_info *ui, unwind_entry_cb_t cb, >>> unw_word_t ip; >>> >>> unw_get_reg(&c, UNW_REG_IP, &ip); >>> + if (ip == prev_ip) >>> + break; >>> + prev_ip = ip; > > hum, how about recursion? > > how about some counter and break after some insane value
I chose > 1 as the insane value. Do you have a suggestion on something else? 5? 10?
> and maybe display some warning.. > > qemu-system-x86 13759 [001] 287663.084967: syscalls:sys_exit_futex: 0x1 > 7f7705fd23ea __lll_unlock_wake (/lib64/libpthread-2.14.90.so) > 7f7705fcf045 _L_unlock_649 (/lib64/libpthread-2.14.90.so) > warning: unwind broken
sure.
David
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