Fix [c54e4a1aeb] (again): High Tcl latencies with fork() in larger systems.

vfork() is now prefered, if available

5 files changed, 178 insertions, 31 deletions

diff --git a/unix/configure b/unix/configure
index 108ac04..553fc73 100755
--- a/unix/configure
+++ b/unix/configure
@@ -8978,7 +8978,112 @@ echo "${ECHO_T}$ac_cv_nolto" >&6
 	CFLAGS_NOLTO=""
     fi
 
-    #AC_CHECK_FUNCS([posix_spawnp])
+    # Check for vfork, posix_spawnp() and friends unconditionally
+
+
+
+
+for ac_func in vfork posix_spawnp posix_spawn_file_actions_adddup2 posix_spawnattr_setflags
+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
+
 
     # FIXME: This subst was left in only because the TCL_DL_LIBS
     # entry in tclConfig.sh uses it. It is not clear why someone
diff --git a/unix/tcl.m4 b/unix/tcl.m4
index d6f1d2b..06d31b8 100644
--- a/unix/tcl.m4
+++ b/unix/tcl.m4
@@ -590,7 +590,6 @@ AC_DEFUN([SC_ENABLE_FRAMEWORK], [
 #		TCL_THREADS
 #		_REENTRANT
 #		_THREAD_SAFE
-#
 #------------------------------------------------------------------------
 
 AC_DEFUN([SC_ENABLE_THREADS], [
@@ -2068,7 +2067,8 @@ dnl # preprocessing tests use only CPPFLAGS.
 	CFLAGS_NOLTO=""
     fi
 
-    #AC_CHECK_FUNCS([posix_spawnp])
+    # Check for vfork, posix_spawnp() and friends unconditionally
+    AC_CHECK_FUNCS(vfork posix_spawnp posix_spawn_file_actions_adddup2 posix_spawnattr_setflags)
 
     # FIXME: This subst was left in only because the TCL_DL_LIBS
     # entry in tclConfig.sh uses it. It is not clear why someone
diff --git a/unix/tclConfig.h.in b/unix/tclConfig.h.in
index 486d8d9..5a64236 100644
--- a/unix/tclConfig.h.in
+++ b/unix/tclConfig.h.in
@@ -174,9 +174,15 @@
 /* Define to 1 if you have the `OSSpinLockLock' function. */
 #undef HAVE_OSSPINLOCKLOCK
 
+/* Define to 1 if you have the `posix_spawnattr_setflags' function. */
+#undef HAVE_POSIX_SPAWNATTR_SETFLAGS
+
 /* Define to 1 if you have the `posix_spawnp' function. */
 #undef HAVE_POSIX_SPAWNP
 
+/* Define to 1 if you have the `posix_spawn_file_actions_adddup2' function. */
+#undef HAVE_POSIX_SPAWN_FILE_ACTIONS_ADDDUP2
+
 /* Define to 1 if you have the `pthread_atfork' function. */
 #undef HAVE_PTHREAD_ATFORK
 
@@ -273,6 +279,9 @@
 /* Define to 1 if you have the <unistd.h> header file. */
 #undef HAVE_UNISTD_H
 
+/* Define to 1 if you have the `vfork' function. */
+#undef HAVE_VFORK
+
 /* Define to 1 if you have the `waitpid' function. */
 #undef HAVE_WAITPID
 
diff --git a/unix/tclUnixPipe.c b/unix/tclUnixPipe.c
index 649fa4d..96ca095 100644
--- a/unix/tclUnixPipe.c
+++ b/unix/tclUnixPipe.c
@@ -14,10 +14,17 @@
 #include "tclInt.h"
 
 #ifdef HAVE_POSIX_SPAWNP
-# include <spawn.h>
+#   if defined(HAVE_POSIX_SPAWN_FILE_ACTIONS_ADDDUP2) \
+	    && defined(HAVE_POSIX_SPAWNATTR_SETFLAGS) \
+	    && !defined(HAVE_VFORK)
+#	include <unistd.h>
+#	include <spawn.h>
+#   else
+#	undef HAVE_POSIX_SPAWNP
+#   endif
 #endif
 
-#ifdef USE_VFORK
+#ifdef HAVE_VFORK
 #define fork vfork
 #endif
 
@@ -417,6 +424,7 @@ TclpCreateProcess(
     int pid, i;
 #if defined(HAVE_POSIX_SPAWNP)
     int childErrno;
+    static int use_spawn = -1;
 #endif
 
     errPipeIn = NULL;
@@ -446,7 +454,7 @@ TclpCreateProcess(
 	newArgv[i] = Tcl_UtfToExternalDString(NULL, argv[i], -1, &dsArray[i]);
     }
 
-#if defined(USE_VFORK) || defined(HAVE_POSIX_SPAWNP)
+#if defined(HAVE_VFORK) || defined(HAVE_POSIX_SPAWNP)
     /*
      * After vfork(), do not call code in the child that changes global state,
      * because it is using the parent's memory space at that point and writes
@@ -467,28 +475,52 @@ TclpCreateProcess(
 #endif
 
 #ifdef HAVE_POSIX_SPAWNP
-    {
+#ifdef _CS_GNU_LIBC_VERSION
+    if (use_spawn < 0) {
+	char conf[32], *p;
+	int major = 0, minor = 0;
+
+	use_spawn = 0;
+	memset(conf, 0, sizeof(conf));
+	confstr(_CS_GNU_LIBC_VERSION, conf, sizeof(conf));
+	p = strchr(conf, ' ');	/* skip "glibc" */
+	if (p != NULL) {
+	    ++p;
+	    if (sscanf(p, "%d.%d", &major, &minor) > 1) {
+		if ((major > 2) || ((major == 2) && (minor >= 24))) {
+		    use_spawn = 1;
+		}
+	    }
+	}
+    }
+#endif
+    status = -1;
+    if (use_spawn) {
 	posix_spawn_file_actions_t actions;
 	posix_spawnattr_t attr;
+	sigset_t sigs;
 
 	posix_spawn_file_actions_init(&actions);
 	posix_spawnattr_init(&attr);
-
-	posix_spawnattr_setflags(&attr, POSIX_SPAWN_SETSIGDEF|
-# ifdef POSIX_SPAWN_USEVFORK
-		POSIX_SPAWN_USEVFORK
-# else
-		0
-# endif
-		);
+	sigfillset(&sigs);
+	sigdelset(&sigs, SIGKILL);
+	sigdelset(&sigs, SIGSTOP);
+
+	posix_spawnattr_setflags(&attr,
+				 POSIX_SPAWN_SETSIGDEF
+#ifdef POSIX_SPAWN_USEVFORK
+				 | POSIX_SPAWN_USEVFORK
+#endif
+				 );
+	posix_spawnattr_setsigdefault(&attr, &sigs);
 
 	posix_spawn_file_actions_adddup2(&actions, GetFd(inputFile), 0);
 	posix_spawn_file_actions_adddup2(&actions, GetFd(outputFile), 1);
 	posix_spawn_file_actions_adddup2(&actions, GetFd(errorFile), 2);
 
-	status = posix_spawnp(&pid, newArgv[0], &actions, &attr, newArgv, environ);
-	childErrno = status;
-
+	status = posix_spawnp(&pid, newArgv[0], &actions, &attr,
+			      newArgv, environ);
+	childErrno = errno;
 	posix_spawn_file_actions_destroy(&actions);
 	posix_spawnattr_destroy(&attr);
 
@@ -498,11 +530,13 @@ TclpCreateProcess(
 	 *  - pid == -1: error
 	 *  - pid > 0: parent process
 	 *
-	 * Mimic fork semantics to minimize changes below
+	 * Mimic fork semantics to minimize changes below,
+	 * but retry with fork() as last ressort.
 	 */
-	if (status != 0) {
-	    pid = -1;
-	}
+    }
+    if (status != 0) {
+	pid = fork();
+	childErrno = errno;
     }
 #else
     pid = fork();
@@ -558,12 +592,9 @@ TclpCreateProcess(
     if (pid == -1) {
 #ifdef HAVE_POSIX_SPAWNP
 	errno = childErrno;
-	Tcl_SetObjResult(interp, Tcl_ObjPrintf(
-		"couldn't execute \"%s\": %s", argv[0], Tcl_PosixError(interp)));
-#else
+#endif
 	Tcl_SetObjResult(interp, Tcl_ObjPrintf(
 		"couldn't fork child process: %s", Tcl_PosixError(interp)));
-#endif
 	goto error;
     }
 
diff --git a/unix/tclUnixPort.h b/unix/tclUnixPort.h
index 711ad4c..486fa23 100644
--- a/unix/tclUnixPort.h
+++ b/unix/tclUnixPort.h
@@ -636,11 +636,13 @@ extern char **		environ;
 	    defined(HAVE_WEAK_IMPORT) && MAC_OS_X_VERSION_MIN_REQUIRED < 1050
 #	warning "Weak import of 64-bit CoreFoundation is not supported, will not run on Mac OS X < 10.5."
 #   endif
-/* For now, test exec-17.1 fails (I/O setup after closing stdout) with
- * posix_spawnp(), but the classic implementation (based on fork()+execvp())
- * works well under macOS quite OK.
- */
-#undef HAVE_POSIX_SPAWNP
+    /*
+     * For now, test exec-17.1 fails (I/O setup after closing stdout) with
+     * posix_spawnp(), but the classic implementation (based on fork()+execvp())
+     * works well under macOS.
+     */
+#   undef HAVE_POSIX_SPAWNP
+#   undef HAVE_VFORK
 #endif /* __APPLE__ */
 
 /*