child of a multithreaded process looping in malloc()

[Edgar Fuß <ef%math.uni-bonn.de@localhost>]

I've a long-standing problem of a process eating cpu time without doing 
anything useful, which, most probably, goes like this:

Of a multi-threaded process,
one thread is in malloc() while another thread fork()s.
(So the child is born with the malloc lock held.)
The child process (becoming single-threaded by the fork) calls malloc().
The child loops forever because there's no other thread to release the lock.

Strictly speaking, malloc(3) is not declared to be async-signal-safe, so a 
threaded program shouldn't call malloc() in a child before fork()ing.
In my case, the code doing the fork/malloc is the Perl interpreter embedded 
into collectd, so there's little I can do about it.

Couldn't malloc simply install a pthread_atfork() handler that releases 
the lock in the child?