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macOS: avoid deadlock inside dyld4 deadlock workaround #49740

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merged 1 commit into from
May 11, 2023
+17 −3
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macOS: avoid deadlock inside dyld4 deadlock workaround #49740

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20 changes: 17 additions & 3 deletions src/signals-mach.c
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Original file line number Diff line number Diff line change
Expand Up @@ -36,6 +36,9 @@ extern int _keymgr_set_lockmode_processwide_ptr(unsigned int key, unsigned int m
extern void _dyld_atfork_prepare(void) __attribute__((weak_import));
extern void _dyld_atfork_parent(void) __attribute__((weak_import));
//extern void _dyld_fork_child(void) __attribute__((weak_import));
extern void _dyld_dlopen_atfork_prepare(void) __attribute__((weak_import));
extern void _dyld_dlopen_atfork_parent(void) __attribute__((weak_import));
//extern void _dyld_dlopen_atfork_child(void) __attribute__((weak_import));

static void attach_exception_port(thread_port_t thread, int segv_only);

Expand Down Expand Up @@ -564,16 +567,23 @@ static int jl_lock_profile_mach(int dlsymlock)
// workaround for old keymgr bugs
void *unused = NULL;
int keymgr_locked = _keymgr_get_and_lock_processwide_ptr_2(KEYMGR_GCC3_DW2_OBJ_LIST, &unused) == 0;
// workaround for new dlsym4 bugs (API and bugs introduced in macOS 12.1)
// workaround for new dlsym4 bugs in the workaround for dlsym bugs: _dyld_atfork_prepare
// acquires its locks in the wrong order, but fortunately we happen to able to guard it
// with this call to force it to prevent that TSAN violation from causing a deadlock
if (dlsymlock && _dyld_dlopen_atfork_prepare != NULL && _dyld_dlopen_atfork_parent != NULL)
_dyld_dlopen_atfork_prepare();
// workaround for new dlsym4 bugs (API and bugs introduced circa macOS 12.1)
if (dlsymlock && _dyld_atfork_prepare != NULL && _dyld_atfork_parent != NULL)
_dyld_atfork_prepare();
return keymgr_locked;
}

static void jl_unlock_profile_mach(int dlsymlock, int keymgr_locked)
{
if (dlsymlock && _dyld_atfork_prepare != NULL && _dyld_atfork_parent != NULL) \
_dyld_atfork_parent(); \
if (dlsymlock && _dyld_atfork_prepare != NULL && _dyld_atfork_parent != NULL)
_dyld_atfork_parent();
if (dlsymlock && _dyld_dlopen_atfork_prepare != NULL && _dyld_dlopen_atfork_parent != NULL)
_dyld_dlopen_atfork_parent();
if (keymgr_locked)
_keymgr_unlock_processwide_ptr(KEYMGR_GCC3_DW2_OBJ_LIST);
jl_unlock_profile();
Expand Down Expand Up @@ -611,13 +621,17 @@ void *mach_profile_listener(void *arg)
break;
}

if (_dyld_dlopen_atfork_prepare != NULL && _dyld_dlopen_atfork_parent != NULL)
_dyld_dlopen_atfork_prepare();
if (_dyld_atfork_prepare != NULL && _dyld_atfork_parent != NULL)
_dyld_atfork_prepare(); // briefly acquire the dlsym lock
host_thread_state_t state;
int valid_thread = jl_thread_suspend_and_get_state2(i, &state);
unw_context_t *uc = (unw_context_t*)&state;
if (_dyld_atfork_prepare != NULL && _dyld_atfork_parent != NULL)
_dyld_atfork_parent(); // quickly release the dlsym lock
if (_dyld_dlopen_atfork_prepare != NULL && _dyld_dlopen_atfork_parent != NULL)
_dyld_dlopen_atfork_parent();
if (!valid_thread)
continue;
if (running) {
Expand Down