Comment 43 for bug 1863162

(In reply to xujing from comment #39)
> I'm sorry, I misled you. I think there is an ABBA deadlock issue in some
> scenarios.
>
> If I have a c++ dynamic library(named libA.so) that contains a global
> object, the global object will call the post-constructor at initialization
> and hold it's own lock(named A_lock) when dlopen loads libA.so. Assume that
> two threads execute the following process：
> Thread1:dlopen(libA.so) => hold dl_load_lock => load libA.so => init
> global
> object from libA.so => wait for hold A_lock
> Thread2:my own code hold A_lock => pthread_create =>
> _dl_allocate_tls_init
> => wait for hold dl_load_lock
> In this case, an ABBA deadlock occurs. Is this a bug?

yes i think this should work (it is a lock ordering
issue between a user and libc internal lock, which
is only possible if user code is run while a libc
lock is held)

note that if you replace pthread_create with dlopen
that deadlocks too. so it's still bug 15686. but it
may be more common than i expected. i think we need
to look at fixing that bug. (fixing the dynamic tls
race of this bug without locks in pthread_create is
very hard, so i don't think we can revert the quoted
patch)