When threads are sharing mm via CLONE_VM (linuxthreads, vfork), there is a
race condition where one thread doing a core dump and synchronizing all
mm-sharing threads for it can deadlock waiting for another thread that just
did an exec and will never synchronize.  This patch makes the exec_mmap
check for a pending core dump and punt the exec to synchronize with that,
as if the core dump had struck before entering the execve system call at
all.
Signed-off-by: Roland McGrath <roland@redhat.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>