Modify the code path of the ifdef NOTYET part of _kse_single_thread():

o  Don't reinitialise the atfork() handler list in the child.  We
   are meant to call the child handler, and on subsequent fork()s
   should call all three functions as normal.
o  Don't reinitialise the thread specific keyed data in the
   child after a fork.  Applications may require this for context.
o  Reinitialise curthread->tlflags after removing ourselves from
   (and reinitialising) the various internal thread lists.
o  Reinitialise __malloc_lock in the child after fork() (to balance
   our explicitly taking the lock prior to the fork()).

With these changes, it is possible to enable the NOTYET code in
thr_kern.c to allow the use of non-async-safe functions after
fork()ing from a threaded program.

Reviewed by:	Daniel Eischen <deischen@freebsd.org>
[_malloc_lock reinitialisation has since been moved to avoid polluting the
!NOTYET code]

2 files changed, 11 insertions, 8 deletions

diff --git a/lib/libkse/thread/thr_init.c b/lib/libkse/thread/thr_init.c
index c143627..e5439ad 100644
--- a/lib/libkse/thread/thr_init.c
+++ b/lib/libkse/thread/thr_init.c
@@ -437,6 +437,7 @@ init_private(void)
 		}
 		_pthread_attr_default.guardsize_attr = _thr_guard_default;
 		_pthread_attr_default.stacksize_attr = _thr_stack_default;
+		TAILQ_INIT(&_thr_atfork_list);
 		init_once = 1;	/* Don't do this again. */
 	} else {
 		/*
@@ -453,7 +454,6 @@ init_private(void)
 	/* Initialize everything else. */
 	TAILQ_INIT(&_thread_list);
 	TAILQ_INIT(&_thread_gc_list);
-	TAILQ_INIT(&_thr_atfork_list);
 	_pthread_mutex_init(&_thr_atfork_mutex, NULL);
 
 	/*
diff --git a/lib/libkse/thread/thr_kern.c b/lib/libkse/thread/thr_kern.c
index d57665e..be763c2 100644
--- a/lib/libkse/thread/thr_kern.c
+++ b/lib/libkse/thread/thr_kern.c
@@ -55,6 +55,9 @@ __FBSDID("$FreeBSD$");
 #include "atomic_ops.h"
 #include "thr_private.h"
 #include "libc_private.h"
+#ifdef NOTYET
+#include "spinlock.h"
+#endif
 
 /* #define DEBUG_THREAD_KERN */
 #ifdef DEBUG_THREAD_KERN
@@ -210,9 +213,9 @@ _kse_single_thread(struct pthread *curthread)
 	struct kse *kse;
 	struct kse_group *kseg;
 	struct pthread *thread;
-	kse_critical_t crit;
-	int i;
 
+	_thr_spinlock_init();
+	*__malloc_lock = (spinlock_t)_SPINLOCK_INITIALIZER;
 	if (__isthreaded) {
 		_thr_rtld_fini();
 		_thr_signal_deinit();
@@ -250,11 +253,8 @@ _kse_single_thread(struct pthread *curthread)
 	curthread->joiner = NULL;		/* no joining threads yet */
 	curthread->refcount = 0;
 	SIGEMPTYSET(curthread->sigpend);	/* clear pending signals */
-	if (curthread->specific != NULL) {
-		free(curthread->specific);
-		curthread->specific = NULL;
-		curthread->specific_data_count = 0;
-	}
+
+	/* Don't free thread-specific data as the caller may require it */
 
 	/* Free the free KSEs: */
 	while ((kse = TAILQ_FIRST(&free_kseq)) != NULL) {
@@ -317,6 +317,9 @@ _kse_single_thread(struct pthread *curthread)
 	curthread->attr.flags &= ~PTHREAD_SCOPE_SYSTEM;
 	curthread->attr.flags |= PTHREAD_SCOPE_PROCESS;
 
+	/* We're no longer part of any lists */
+	curthread->tlflags = 0;
+
 	/*
 	 * After a fork, we are still operating on the thread's original
 	 * stack.  Don't clear the THR_FLAGS_USER from the thread's