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Unwinding fix - remove heuristic around infinite loop detection #478

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Unwinding fix - remove heuristic around infinite loop detection #478

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26 changes: 1 addition & 25 deletions src/unwind_dwfl.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -42,23 +42,6 @@ void trace_unwinding_end(UnwindState *us) {
}
}

bool is_infinite_loop(UnwindState *us) {
UnwindOutput &output = us->output;
uint64_t const nb_locs = output.locs.size();
unsigned const nb_frames_to_check = 3;
if (nb_locs <= nb_frames_to_check) {
return false;
}
for (unsigned i = 1; i < nb_frames_to_check; ++i) {
FunLoc const &n_minus_one_loc = output.locs[nb_locs - i];
FunLoc const &n_minus_two_loc = output.locs[nb_locs - i - 1];
if (n_minus_one_loc.ip != n_minus_two_loc.ip) {
return false;
}
}
return true;
}

// check for runtime symbols provided in /tmp files
DDRes add_runtime_symbol_frame(UnwindState *us, const Dso &dso, ElfAddress_t pc,
std::string_view jitdump_path);
Expand Down Expand Up @@ -184,16 +167,9 @@ int frame_cb(Dwfl_Frame *dwfl_frame, void *arg) {
#ifdef DEBUG
LG_NFO("Begin depth %lu", us->output.locs.size());
#endif
int const dwfl_error_value = dwfl_errno();
if (dwfl_error_value) {
// Check if dwarf unwinding was a failure we can get stuck in infinite loops
if (is_infinite_loop(us)) {
LG_DBG("Break out of unwinding (possible infinite loop)");
return DWARF_CB_ABORT;
}
}
#ifdef DEBUG
// We often fallback to frame pointer unwinding (which logs an error)
int const dwfl_error_value = dwfl_errno();
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@r1viollet r1viollet Dec 4, 2025

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I have a minor doubt on how useful it is to read the errno value.

if (dwfl_error_value) {
LG_DBG("Error flagged at depth = %lu -- %d Error:%s ",
us->output.locs.size(), dwfl_error_value,
Expand Down