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Use thread local for libunwind GetStackTrace() reentrancy protection #161

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Oct 31, 2019
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Use thread local for libunwind GetStackTrace() reentrancy protection #161

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9 changes: 6 additions & 3 deletions src/stacktrace_libunwind-inl.h
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Original file line number Diff line number Diff line change
Expand Up @@ -49,7 +49,9 @@ _START_GOOGLE_NAMESPACE_
// recursive request, we'd end up with infinite recursion or deadlock.
// Luckily, it's safe to ignore those subsequent traces. In such
// cases, we return 0 to indicate the situation.
static bool g_now_entering = false;
// We can use the GCC __thread syntax here since libunwind is not supported on
// Windows.
static __thread bool g_tl_entered; // Initialized to false.

// If you change this function, also change GetStackFrames below.
int GetStackTrace(void** result, int max_depth, int skip_count) {
Expand All @@ -58,9 +60,10 @@ int GetStackTrace(void** result, int max_depth, int skip_count) {
unw_cursor_t cursor;
unw_context_t uc;

if (sync_val_compare_and_swap(&g_now_entering, false, true)) {
if (g_tl_entered) {
return 0;
}
g_tl_entered = true;

unw_getcontext(&uc);
RAW_CHECK(unw_init_local(&cursor, &uc) >= 0, "unw_init_local failed");
Expand All @@ -80,7 +83,7 @@ int GetStackTrace(void** result, int max_depth, int skip_count) {
break;
}

g_now_entering = false;
g_tl_entered = false;
return n;
}

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