Revert incorrect patch to wait_any and instead use waitpid to avoid blocking.

5 files changed, 31 insertions, 6 deletions

diff --git a/ChangeLog b/ChangeLog
index 5d293bf8..a692e5b1 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,13 @@
+2013-07-04         Andrew J. Schorr     <aschorr@telemetry-investments.com>
+
+	* configure.ac (AC_CHECK_FUNCS): Add a check for waitpid.
+	* io.c (wait_any): Enhance comment to explain why we loop reaping all
+	exited children when the argument is zero.  When available, use waitpid
+	with WNOHANG to avoid blocking.  Remove my previous incorrect patch to
+	exit after reaping the first child.  The function is intended to
+	wait for all children, since we are not careful about reaping children
+	as soon as they die.
+
 2013-07-02         Andrew J. Schorr     <aschorr@telemetry-investments.com>
 
 	* gawkapi.h (gawk_api): Remove unused api_lookup_file hook.
diff --git a/configh.in b/configh.in
index f6540a45..68d5bf76 100644
--- a/configh.in
+++ b/configh.in
@@ -296,6 +296,9 @@
 /* Define to 1 if you have the `vprintf' function. */
 #undef HAVE_VPRINTF
 
+/* Define to 1 if you have the `waitpid' function. */
+#undef HAVE_WAITPID
+
 /* Define to 1 if you have the <wchar.h> header file. */
 #undef HAVE_WCHAR_H
 
diff --git a/configure b/configure
index 0e5a9303..fccfcea0 100755
--- a/configure
+++ b/configure
@@ -10020,7 +10020,7 @@ for ac_func in atexit btowc fmod getgrent getgroups grantpt \
 	memcmp memcpy memcpy_ulong memmove memset \
 	memset_ulong mkstemp posix_openpt setenv setlocale setsid snprintf strchr \
 	strerror strftime strncasecmp strcoll strtod strtoul \
-	system tmpfile towlower towupper tzset usleep wcrtomb \
+	system tmpfile towlower towupper tzset usleep waitpid wcrtomb \
 	wcscoll wctype
 do :
   as_ac_var=`$as_echo "ac_cv_func_$ac_func" | $as_tr_sh`
diff --git a/configure.ac b/configure.ac
index b401cb40..ba242c51 100644
--- a/configure.ac
+++ b/configure.ac
@@ -276,7 +276,7 @@ AC_CHECK_FUNCS(atexit btowc fmod getgrent getgroups grantpt \
 	memcmp memcpy memcpy_ulong memmove memset \
 	memset_ulong mkstemp posix_openpt setenv setlocale setsid snprintf strchr \
 	strerror strftime strncasecmp strcoll strtod strtoul \
-	system tmpfile towlower towupper tzset usleep wcrtomb \
+	system tmpfile towlower towupper tzset usleep waitpid wcrtomb \
 	wcscoll wctype)
 dnl this check is for both mbrtowc and the mbstate_t type, which is good
 AC_FUNC_MBRTOWC
diff --git a/io.c b/io.c
index 0ba36451..42c92e47 100644
--- a/io.c
+++ b/io.c
@@ -2168,7 +2168,16 @@ use_pipes:
 
 #ifndef PIPES_SIMULATED		/* real pipes */
 
-/* wait_any --- wait for a child process, close associated pipe */
+/*
+ * wait_any --- if the argument pid is 0, wait for all child processes that
+ * have exited.  We loop to make sure to reap all children that have exited to
+ * minimize the risk of running out of process slots.  Since we don't process
+ * SIGCHLD, we do not immediately reap exited children.  So when we get here,
+ * we want to reap any that have piled up.
+ *
+ * Note: on platforms that do not support waitpid with WNOHANG, when called with
+ * a zero argument, this function will hang until all children have exited.
+ */
 
 static int
 wait_any(int interesting)	/* pid of interest, if any */
@@ -2198,7 +2207,11 @@ wait_any(int interesting)	/* pid of interest, if any */
 	hstat = signal(SIGHUP, SIG_IGN);
 	qstat = signal(SIGQUIT, SIG_IGN);
 	for (;;) {
-# ifdef HAVE_SYS_WAIT_H	/* POSIX compatible sys/wait.h */
+# if defined(HAVE_WAITPID) && defined(WNOHANG)
+		if ((pid = waitpid(-1, & status, WNOHANG)) == 0)
+			/* No children have exited */
+			break;
+# elif defined(HAVE_SYS_WAIT_H)	/* POSIX compatible sys/wait.h */
 		pid = wait(& status);
 # else
 		pid = wait((union wait *) & status);
@@ -2210,13 +2223,12 @@ wait_any(int interesting)	/* pid of interest, if any */
 				if (pid == redp->pid) {
 					redp->pid = -1;
 					redp->status = status;
-					goto finished;
+					break;
 				}
 		}
 		if (pid == -1 && errno == ECHILD)
 			break;
 	}
-finished:
 	signal(SIGHUP, hstat);
 	signal(SIGQUIT, qstat);
 #endif