[buyemune-sys]

The problem

A module whose TLS is placed in the static window (the pad) gets an initialized copy of its template only in the thread that called dlopen and, through musl's __copy_tls, in threads created after the load. Threads that were already running see zeroes instead of the initial values.

The README describes this as an initial-exec-only restriction. In fact every module that fits is placed in the window (Loader::allocateStaticTls, lib/elf_loader.cpp:1540), so ordinary general-dynamic modules (the -fPIC default) are affected too:

                            glibc   solo main
IE module, earlier thread:   42        0
GD module, earlier thread:   42        0

glibc initializes the block in every live thread in this situation (_dl_init_static_tls). For an application server that loads plugins on demand, after its worker threads already exist, this is the normal case.

Also: the README says the arena is 16 KiB, while SOLO_TLS_PAD in the code is 1 MiB (lib/musl_tls.c:49).

The fix

After registering the module, soloTlsRegister (lib/musl_tls.c:183) walks musl's thread ring under __tl_lock and seeds the block at the same thread-pointer offset in each thread. All of it runs under __inhibit_ptc(), as musl's own dlopen does. The reason: pthread_create allocates and copies a new thread's TLS before adding the thread to the list, so a thread created concurrently with the registration would otherwise miss both the template and the seeding. The real __inhibit_ptc/__acquire_ptc already get linked in from src/thread/lock_ptc.c.

README: the restriction is dropped and the arena size is corrected to 1 MiB.

Test

The existing test in tst/smoke.cpp locked in the old behavior (pre-existing thread saw %d instead of zeroed TLS). Now the "parked" thread, created before the IE module loads, runs the full glibc_ie_selfcheck: the .tdata template, zeroed .tbss, the buffer, alignment, and a write.

• on main (new test only): pre-existing thread initial-exec selfcheck failed: 1;
• with the fix: ./build test passes, and standalone IE/GD examples read 42 in every thread.