glibc: add ld.so locks in _libc_fork

The patch in this Bugzilla entry was requested by a customer:
  https://sourceware.org/bugzilla/show_bug.cgi?id=4578
  https://www.sourceware.org/bugzilla/show_bug.cgi?id=19282

If a thread happens to hold dl_load_lock and have r_state set to RT_ADD or
RT_DELETE at the time another thread calls fork(), then the child exit code
from fork (in nptl/sysdeps/unix/sysv/linux/fork.c in our case) re-initializes
dl_load_lock but does not restore r_state to RT_CONSISTENT. If the child
subsequently requires ld.so functionality before calling exec(), then the
assertion will fire.

The patch acquires dl_load_lock on entry to fork() and releases it on exit
from the parent path.  The child path is initialized as currently done.
This is essentially pthreads_atfork, but forced to be first because the
acquisition of dl_load_lock must happen before malloc_atfork is active
to avoid a deadlock.

The __libc_fork() code reset dl_load_lock, but it also needed to reset
dl_load_write_lock.

Signed-off-by: Zhixiong Chi <zhixiong.chi@windriver.com>
Signed-off-by: Ross Burton <ross.burton@intel.com>

0 files changed, 0 insertions, 0 deletions