Increase fork signal safety for single-threaded processes [BZ #19703]

This provides a band-aid and addresses the scenario where fork is
called from a signal handler while the process is in the malloc
subsystem (or has acquired the libio list lock).  It does not
address the general issue of async-signal-safety of fork;
multi-threaded processes are not covered, and some glibc
subsystems have fork handlers which are not async-signal-safe.

1 files changed, 10 insertions, 0 deletions

diff --git a/ChangeLog b/ChangeLog
index dee85ca..e623247 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,15 @@
 2016-05-12  Florian Weimer  <fweimer@redhat.com>
 
+	[BZ #19703]
+	Partially async-signal-safe fork for single-threaded processes.
+	* sysdeps/nptl/fork.c (__libc_fork): Introduce multiple_threads
+	variable.  Do not acquire and reset/release malloc and libio locks
+	in single-threaded processes.
+	* malloc/tst-mallocfork2.c: New file.
+	* malloc/Makefile (tests): Add it.
+
+2016-05-12  Florian Weimer  <fweimer@redhat.com>
+
 	* sysdeps/posix/getaddrinfo.c (gaih_inet_serv): Add tmpbuf
 	argument.  Use scratch buffer instead of extend_alloca.
 	(gethosts): Use scratch buffer instead of extend_alloca.