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backtrace: Refactor ast_bt_get_symbols so it doesn't crash

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We've been seeing crashes in libbfd when we attempt to generate
a stack trace from multiple threads.  It turns out that libbfd
is NOT thread-safe.  It can cache the bfd structure and give it to
multiple threads without protecting itself.  To get around this,
we've added a global mutex around the bfd functions and also have
refactored the use of those functions to be more efficient and
to provide more information about inlined functions.

Also added a few more tests to test_pbx.c.  One just calls
ast_assert() and the other calls ast_log_backtrace().  Neither are
run by default.

WARNING:  This change necessitated changing the return value of
ast_bt_get_symbols() from an array of strings to a VECTOR of
strings.  However, the use of this function outside Asterisk is not
likely.

ASTERISK-28140

Change-Id: I79d02862ddaa2423a0809caa4b3b85c128131621
This commit is contained in:
George Joseph
2018-11-08 08:53:44 -07:00
parent fa048183aa
commit ece5f8015f
10 changed files with 318 additions and 183 deletions
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8
main/astmm.c
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@@ -191,7 +191,7 @@ AST_MUTEX_DEFINE_STATIC_NOTRACKING(reglock);
static void print_backtrace(struct ast_bt *bt)
{
int i = 0;
char **strings;
struct ast_vector_string *strings;
if (!bt) {
return;
@@ -199,10 +199,10 @@ static void print_backtrace(struct ast_bt *bt)
if ((strings = ast_bt_get_symbols(bt->addresses, bt->num_frames))) {
astmm_log("Memory allocation backtrace:\n");
for (i = 3; i < bt->num_frames - 2; i++) {
astmm_log("#%d: [%p] %s\n", i - 3, bt->addresses[i], strings[i]);
for (i = 3; i < AST_VECTOR_SIZE(strings) - 2; i++) {
astmm_log("#%d: %s\n", i - 3, AST_VECTOR_GET(strings, i));
}
ast_std_free(strings);
ast_bt_free_symbols(strings);
}
}