Subject: Use pthread_atfork() when available.

From: "jan.nijtmans" <[email-masked]>
Date: Mon, 22 Jul 2013 10:57:44 +0000

---
 unix/configure      | 209 +++++++++++++++++++++++++++-------------------------
 unix/configure.in   |   7 +-
 unix/tclUnixNotfy.c |  90 +++++++++++++++++++++-
 3 files changed, 202 insertions(+), 104 deletions(-)

diff --git a/unix/configure b/unix/configure
index 6faa7d8..ee194b7 100755
--- a/unix/configure
+++ b/unix/configure
@@ -16759,6 +16759,113 @@ done

 #--------------------------------------------------------------------
+# Check for support of pthread_atfork function
+#--------------------------------------------------------------------
+
+
+for ac_func in pthread_atfork
+do
+as_ac_var=`echo "ac_cv_func_$ac_func" | $as_tr_sh`
+echo "$as_me:$LINENO: checking for $ac_func" >&5
+echo $ECHO_N "checking for $ac_func... $ECHO_C" >&6
+if eval "test \"\${$as_ac_var+set}\" = set"; then
+  echo $ECHO_N "(cached) $ECHO_C" >&6
+else
+  cat >conftest.$ac_ext <<_ACEOF
+/* confdefs.h.  */
+_ACEOF
+cat confdefs.h >>conftest.$ac_ext
+cat >>conftest.$ac_ext <<_ACEOF
+/* end confdefs.h.  */
+/* Define $ac_func to an innocuous variant, in case <limits.h> declares $ac_func.
+   For example, HP-UX 11i <limits.h> declares gettimeofday.  */
+#define $ac_func innocuous_$ac_func
+
+/* System header to define __stub macros and hopefully few prototypes,
+    which can conflict with char $ac_func (); below.
+    Prefer <limits.h> to <assert.h> if __STDC__ is defined, since
+    <limits.h> exists even on freestanding compilers.  */
+
+#ifdef __STDC__
+# include <limits.h>
+#else
+# include <assert.h>
+#endif
+
+#undef $ac_func
+
+/* Override any gcc2 internal prototype to avoid an error.  */
+#ifdef __cplusplus
+extern "C"
+{
+#endif
+/* We use char because int might match the return type of a gcc2
+   builtin and then its argument prototype would still apply.  */
+char $ac_func ();
+/* The GNU C library defines this for functions which it implements
+    to always fail with ENOSYS.  Some functions are actually named
+    something starting with __ and the normal name is an alias.  */
+#if defined (__stub_$ac_func) || defined (__stub___$ac_func)
+choke me
+#else
+char (*f) () = $ac_func;
+#endif
+#ifdef __cplusplus
+}
+#endif
+
+int
+main ()
+{
+return f != $ac_func;
+  ;
+  return 0;
+}
+_ACEOF
+rm -f conftest.$ac_objext conftest$ac_exeext
+if { (eval echo "$as_me:$LINENO: \"$ac_link\"") >&5
+  (eval $ac_link) 2>conftest.er1
+  ac_status=$?
+  grep -v '^ *+' conftest.er1 >conftest.err
+  rm -f conftest.er1
+  cat conftest.err >&5
+  echo "$as_me:$LINENO: \$? = $ac_status" >&5
+  (exit $ac_status); } &&
+	 { ac_try='test -z "$ac_c_werror_flag"
+			 || test ! -s conftest.err'
+  { (eval echo "$as_me:$LINENO: \"$ac_try\"") >&5
+  (eval $ac_try) 2>&5
+  ac_status=$?
+  echo "$as_me:$LINENO: \$? = $ac_status" >&5
+  (exit $ac_status); }; } &&
+	 { ac_try='test -s conftest$ac_exeext'
+  { (eval echo "$as_me:$LINENO: \"$ac_try\"") >&5
+  (eval $ac_try) 2>&5
+  ac_status=$?
+  echo "$as_me:$LINENO: \$? = $ac_status" >&5
+  (exit $ac_status); }; }; then
+  eval "$as_ac_var=yes"
+else
+  echo "$as_me: failed program was:" >&5
+sed 's/^/| /' conftest.$ac_ext >&5
+
+eval "$as_ac_var=no"
+fi
+rm -f conftest.err conftest.$ac_objext \
+      conftest$ac_exeext conftest.$ac_ext
+fi
+echo "$as_me:$LINENO: result: `eval echo '${'$as_ac_var'}'`" >&5
+echo "${ECHO_T}`eval echo '${'$as_ac_var'}'`" >&6
+if test `eval echo '${'$as_ac_var'}'` = yes; then
+  cat >>confdefs.h <<_ACEOF
+#define `echo "HAVE_$ac_func" | $as_tr_cpp` 1
+_ACEOF
+
+fi
+done
+
+
+#--------------------------------------------------------------------
 # Check for support of isnan() function or macro
 #--------------------------------------------------------------------
 
@@ -17439,108 +17546,6 @@ _ACEOF
 fi
 done
 
-
-for ac_func in pthread_atfork
-do
-as_ac_var=`echo "ac_cv_func_$ac_func" | $as_tr_sh`
-echo "$as_me:$LINENO: checking for $ac_func" >&5
-echo $ECHO_N "checking for $ac_func... $ECHO_C" >&6
-if eval "test \"\${$as_ac_var+set}\" = set"; then
-  echo $ECHO_N "(cached) $ECHO_C" >&6
-else
-  cat >conftest.$ac_ext <<_ACEOF
-/* confdefs.h.  */
-_ACEOF
-cat confdefs.h >>conftest.$ac_ext
-cat >>conftest.$ac_ext <<_ACEOF
-/* end confdefs.h.  */
-/* Define $ac_func to an innocuous variant, in case <limits.h> declares $ac_func.
-   For example, HP-UX 11i <limits.h> declares gettimeofday.  */
-#define $ac_func innocuous_$ac_func
-
-/* System header to define __stub macros and hopefully few prototypes,
-    which can conflict with char $ac_func (); below.
-    Prefer <limits.h> to <assert.h> if __STDC__ is defined, since
-    <limits.h> exists even on freestanding compilers.  */
-
-#ifdef __STDC__
-# include <limits.h>
-#else
-# include <assert.h>
-#endif
-
-#undef $ac_func
-
-/* Override any gcc2 internal prototype to avoid an error.  */
-#ifdef __cplusplus
-extern "C"
-{
-#endif
-/* We use char because int might match the return type of a gcc2
-   builtin and then its argument prototype would still apply.  */
-char $ac_func ();
-/* The GNU C library defines this for functions which it implements
-    to always fail with ENOSYS.  Some functions are actually named
-    something starting with __ and the normal name is an alias.  */
-#if defined (__stub_$ac_func) || defined (__stub___$ac_func)
-choke me
-#else
-char (*f) () = $ac_func;
-#endif
-#ifdef __cplusplus
-}
-#endif
-
-int
-main ()
-{
-return f != $ac_func;
-  ;
-  return 0;
-}
-_ACEOF
-rm -f conftest.$ac_objext conftest$ac_exeext
-if { (eval echo "$as_me:$LINENO: \"$ac_link\"") >&5
-  (eval $ac_link) 2>conftest.er1
-  ac_status=$?
-  grep -v '^ *+' conftest.er1 >conftest.err
-  rm -f conftest.er1
-  cat conftest.err >&5
-  echo "$as_me:$LINENO: \$? = $ac_status" >&5
-  (exit $ac_status); } &&
-	 { ac_try='test -z "$ac_c_werror_flag"
-			 || test ! -s conftest.err'
-  { (eval echo "$as_me:$LINENO: \"$ac_try\"") >&5
-  (eval $ac_try) 2>&5
-  ac_status=$?
-  echo "$as_me:$LINENO: \$? = $ac_status" >&5
-  (exit $ac_status); }; } &&
-	 { ac_try='test -s conftest$ac_exeext'
-  { (eval echo "$as_me:$LINENO: \"$ac_try\"") >&5
-  (eval $ac_try) 2>&5
-  ac_status=$?
-  echo "$as_me:$LINENO: \$? = $ac_status" >&5
-  (exit $ac_status); }; }; then
-  eval "$as_ac_var=yes"
-else
-  echo "$as_me: failed program was:" >&5
-sed 's/^/| /' conftest.$ac_ext >&5
-
-eval "$as_ac_var=no"
-fi
-rm -f conftest.err conftest.$ac_objext \
-      conftest$ac_exeext conftest.$ac_ext
-fi
-echo "$as_me:$LINENO: result: `eval echo '${'$as_ac_var'}'`" >&5
-echo "${ECHO_T}`eval echo '${'$as_ac_var'}'`" >&6
-if test `eval echo '${'$as_ac_var'}'` = yes; then
-  cat >>confdefs.h <<_ACEOF
-#define `echo "HAVE_$ac_func" | $as_tr_cpp` 1
-_ACEOF
-
-fi
-done
-
     fi
 
 cat >>confdefs.h <<\_ACEOF
diff --git a/unix/configure.in b/unix/configure.in
index e22a7d3..f47b882 100644
--- a/unix/configure.in
+++ b/unix/configure.in
@@ -491,6 +491,12 @@ SC_ENABLE_LANGINFO
 AC_CHECK_FUNCS(chflags)
 
 #--------------------------------------------------------------------
+# Check for support of pthread_atfork function
+#--------------------------------------------------------------------
+
+AC_CHECK_FUNCS(pthread_atfork)
+
+#--------------------------------------------------------------------
 # Check for support of isnan() function or macro
 #--------------------------------------------------------------------
 
@@ -513,7 +519,6 @@ if test "`uname -s`" = "Darwin" ; then
     if test $tcl_corefoundation = yes; then
 	AC_CHECK_HEADERS(libkern/OSAtomic.h)
 	AC_CHECK_FUNCS(OSSpinLockLock)
-	AC_CHECK_FUNCS(pthread_atfork)
     fi
     AC_DEFINE(USE_VFORK, 1, [Should we use vfork() instead of fork()?])
     AC_DEFINE(TCL_DEFAULT_ENCODING, "utf-8",
diff --git a/unix/tclUnixNotfy.c b/unix/tclUnixNotfy.c
index 6e8b5fa..f414c3f 100644
--- a/unix/tclUnixNotfy.c
+++ b/unix/tclUnixNotfy.c
@@ -202,7 +202,13 @@ static Tcl_ThreadId notifierThread;
 
 #ifdef TCL_THREADS
 static void	NotifierThreadProc(ClientData clientData);
-#endif
+#ifdef HAVE_PTHREAD_ATFORK
+static int	atForkInit = 0;
+static void	AtForkPrepare(void);
+static void	AtForkParent(void);
+static void	AtForkChild(void);
+#endif /* HAVE_PTHREAD_ATFORK */
+#endif /* TCL_THREADS */
 static int	FileHandlerEventProc(Tcl_Event *evPtr, int flags);
 
 /*
@@ -276,6 +282,21 @@ Tcl_InitNotifier(void)
      */
 
     Tcl_MutexLock(&notifierMutex);
+#ifdef HAVE_PTHREAD_ATFORK
+    /*
+     * Install pthread_atfork handlers to reinitialize the notifier in the
+     * child of a fork.
+     */
+
+    if (!atForkInit) {
+	int result = pthread_atfork(AtForkPrepare, AtForkParent, AtForkChild);
+
+	if (result) {
+	    Tcl_Panic("Tcl_InitNotifier: pthread_atfork failed");
+	}
+	atForkInit = 1;
+    }
+#endif
     /*
      * Check if my process id changed, e.g. I was forked
      * In this case, restart the notifier thread and close the
@@ -1251,6 +1272,73 @@ NotifierThreadProc(
 
     TclpThreadExit (0);
 }
+
+#ifdef HAVE_PTHREAD_ATFORK
+/*
+ *----------------------------------------------------------------------
+ *
+ * AtForkPrepare --
+ *
+ *	Lock the notifier in preparation for a fork.
+ *
+ * Results:
+ *	None.
+ *
+ * Side effects:
+ *	None.
+ *
+ *----------------------------------------------------------------------
+ */
+
+static void
+AtForkPrepare(void)
+{
+}
+
+/*
+ *----------------------------------------------------------------------
+ *
+ * AtForkParent --
+ *
+ *	Unlock the notifier in the parent after a fork.
+ *
+ * Results:
+ *	None.
+ *
+ * Side effects:
+ *	None.
+ *
+ *----------------------------------------------------------------------
+ */
+
+static void
+AtForkParent(void)
+{
+}
+
+/*
+ *----------------------------------------------------------------------
+ *
+ * AtForkChild --
+ *
+ *	Unlock and reinstall the notifier in the child after a fork.
+ *
+ * Results:
+ *	None.
+ *
+ * Side effects:
+ *	None.
+ *
+ *----------------------------------------------------------------------
+ */
+
+static void
+AtForkChild(void)
+{
+    Tcl_InitNotifier();
+}
+#endif /* HAVE_PTHREAD_ATFORK */
+
 #endif /* TCL_THREADS */
 
 #endif /* HAVE_COREFOUNDATION */
-- 
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