[Support] Don't take a lock in CrashRecoverySignalHandler (#219529)
Disable() locks a mutex with static storage duration, which is not safe
from a signal handler. When the signal arrives during exit(), after
static destructors have run, the mutex is already destroyed, causing
pthread_mutex_lock returns EINVAL and in turn causing libc++ to throw.
To make matters worse, without exceptions, the throw becomes a
std::terminate, which happens before uninstallExceptionOrSignalHandlers.
Because the signal handler is installed without SA_RESETHAND, every call
to abort() re-enters the handler and throws again.
Inline the two statements Disable() performs. Racing with another thread
here doesn't matter, as the previous comment noted.
llvm-project
c36234b2 - [Support] Don't take a lock in CrashRecoverySignalHandler (#219529)
