perl built with USE_ITHREADS can deadlock during fork() or backticks

since it doesn't ensure threads other than the one calling fork()
aren't holding any locks; the fix is to use pthread_atfork() to
hold global locks

building perl with -Dusemymalloc exacerbates the problem since
Perl_malloc() holds a mutex, and perl's exec() calls New()

XXX the code in win32thread.h may be needed on platforms that have
no pthread_atfork()

p4raw-id: //depot/perl@11151

1 files changed, 9 insertions, 0 deletions

diff --git a/thread.h b/thread.h
index 87fcdbe185..a1e8fdc65b 100644
--- a/thread.h
+++ b/thread.h
@@ -302,6 +302,11 @@
     } STMT_END
 #endif
 
+#ifndef PTHREAD_ATFORK
+#  define PTHREAD_ATFORK(prepare,parent,child)			\
+    pthread_atfork(prepare,parent,child)
+#endif
+
 #ifndef THREAD_RET_TYPE
 #  define THREAD_RET_TYPE	void *
 #  define THREAD_RET_CAST(p)	((void *)(p))
@@ -456,3 +461,7 @@ typedef struct condpair {
 #ifndef INIT_THREADS
 #  define INIT_THREADS NOOP
 #endif
+
+#ifndef PTHREAD_ATFORK
+#  define PTHREAD_ATFORK(prepare,parent,child)	NOOP
+#endif