[SV 46261] Use pselect() for jobserver where supported.

* Makefile.am, configure.ac: Check for pselect() and sys/select.h.
* main.c (main): Block SIGCHLD if we have pselect() support.
* posixos.c (jobserver_acquire): If we support pselect() then use
it to query the jobserver pipe, while also listening for SIGCHLD.
Also pselect() supports a timeout so avoid alarm() calls.

Makefile.am

@@ -16,8 +16,8 @@
 # You should have received a copy of the GNU General Public License along with
 # this program.  If not, see <http://www.gnu.org/licenses/>.
 
-AUTOMAKE_OPTIONS = 1.8 dist-bzip2 check-news
-ACLOCAL_AMFLAGS	=  -I config
+AUTOMAKE_OPTIONS = dist-bzip2 silent-rules std-options
+ACLOCAL_AMFLAGS = -I config
 
 MAKE_HOST =	@MAKE_HOST@
 

configure.ac

@@ -18,7 +18,7 @@
 
 AC_INIT([GNU make],[4.1.90],[bug-make@gnu.org])
 
-AC_PREREQ([2.62])
+AC_PREREQ([2.69])
 
 # Autoconf setup
 AC_CONFIG_AUX_DIR([config])
@@ -29,7 +29,7 @@ AC_CONFIG_HEADERS([config.h])
 # We have to enable "foreign" because ChangeLog is auto-generated
 # We cannot enable -Werror because gettext 0.18.1 has invalid content
 # When we update gettext to 0.18.3 or better we can add it again.
-AM_INIT_AUTOMAKE([1.11.1 silent-rules foreign -Wall])
+AM_INIT_AUTOMAKE([1.15 foreign -Werror -Wall])
 
 # Checks for programs.
 AC_USE_SYSTEM_EXTENSIONS
@@ -51,7 +51,7 @@ AC_ISC_POSIX
 AC_MINIX
 
 # Enable gettext, in "external" mode.
-AM_GNU_GETTEXT_VERSION([0.18.1])
+AM_GNU_GETTEXT_VERSION([0.19.4])
 AM_GNU_GETTEXT([external])
 
 # This test must come as early as possible after the compiler configuration
@@ -68,7 +68,8 @@ AC_HEADER_DIRENT
 AC_HEADER_STAT
 AC_HEADER_TIME
 AC_CHECK_HEADERS([stdlib.h locale.h unistd.h limits.h fcntl.h string.h \
-                  memory.h sys/param.h sys/resource.h sys/time.h sys/timeb.h])
+                  memory.h sys/param.h sys/resource.h sys/time.h sys/timeb.h \
+                  sys/select.h])
 
 AM_PROG_CC_C_O
 AC_C_CONST
@@ -135,7 +136,7 @@ AC_CHECK_FUNCS([strdup strndup mkstemp mktemp fdopen fileno \
                 dup dup2 getcwd realpath sigsetmask sigaction \
                 getgroups seteuid setegid setlinebuf setreuid setregid \
                 getrlimit setrlimit setvbuf pipe strerror strsignal \
-                lstat readlink atexit isatty ttyname])
+                lstat readlink atexit isatty ttyname pselect])
 
 # We need to check declarations, not just existence, because on Tru64 this
 # function is not declared without special flags, which themselves cause

job.c

@@ -527,10 +527,11 @@ child_error (struct child *child,
 
 /* Handle a dead child.  This handler may or may not ever be installed.
 
-   If we're using the jobserver feature, we need it.  First, installing it
-   ensures the read will interrupt on SIGCHLD.  Second, we close the dup'd
-   read FD to ensure we don't enter another blocking read without reaping all
-   the dead children.  In this case we don't need the dead_children count.
+   If we're using the jobserver feature without pselect(), we need it.
+   First, installing it ensures the read will interrupt on SIGCHLD.  Second,
+   we close the dup'd read FD to ensure we don't enter another blocking read
+   without reaping all the dead children.  In this case we don't need the
+   dead_children count.
 
    If we don't have either waitpid or wait3, then make is unreliable, but we
    use the dead_children count to reap children as best we can.  */
@@ -548,10 +549,6 @@ child_handler (int sig UNUSED)
   /* The signal handler must called only once! */
   signal (SIGCHLD, SIG_DFL);
 #endif
-
-  /* This causes problems if the SIGCHLD interrupts a printf().
-  DB (DB_JOBS, (_("Got a SIGCHLD; %u unreaped children.\n"), dead_children));
-  */
 }
 
 extern pid_t shell_function_pid;

main.c

@@ -1870,6 +1870,18 @@ main (int argc, char **argv, char **envp)
     bsd_signal (SIGCLD, child_handler);
 # endif
   }
+
+#ifdef HAVE_PSELECT
+  /* If we have pselect() then we need to block SIGCHLD so it's deferred.  */
+  {
+    sigset_t block;
+    sigemptyset (&block);
+    sigaddset (&block, SIGCHLD);
+    if (sigprocmask (SIG_SETMASK, &block, NULL) < 0)
+      pfatal_with_name ("sigprocmask(SIG_SETMASK, SIGCHLD)");
+  }
+#endif
+
 #endif
 #endif
 

output.c

@@ -46,7 +46,7 @@ unsigned int stdio_traced = 0;
 
 #define OUTPUT_ISSET(_out) ((_out)->out >= 0 || (_out)->err >= 0)
 
-#ifdef HAVE_FCNTL
+#ifdef HAVE_FCNTL_H
 # define STREAM_OK(_s) ((fcntl (fileno (_s), F_GETFD) != -1) || (errno != EBADF))
 #else
 # define STREAM_OK(_s) 1

posixos.c

@@ -21,6 +21,9 @@ this program.  If not, see <http://www.gnu.org/licenses/>.  */
 #ifdef HAVE_FCNTL_H
 # include <fcntl.h>
 #endif
+#if defined(HAVE_PSELECT) && defined(HAVE_SYS_SELECT_H)
+# include <sys/select.h>
+#endif
 
 #include "debug.h"
 #include "job.h"
@@ -33,7 +36,9 @@ this program.  If not, see <http://www.gnu.org/licenses/>.  */
 /* These track the state of the jobserver pipe.  Passed to child instances.  */
 static int job_fds[2] = { -1, -1 };
 
-/* Used to signal read() that a SIGCHLD happened.  Always CLOEXEC.  */
+/* Used to signal read() that a SIGCHLD happened.  Always CLOEXEC.
+   If we use pselect() this will never be created and always -1.
+ */
 static int job_rfd = -1;
 
 /* Token written to the pipe (could be any character...)  */
@@ -42,11 +47,16 @@ static char token = '+';
 static int
 make_job_rfd ()
 {
+#ifdef HAVE_PSELECT
+  /* Pretend we succeeded.  */
+  return 0;
+#else
   EINTRLOOP (job_rfd, dup (job_fds[0]));
   if (job_rfd >= 0)
     CLOSE_ON_EXEC (job_rfd);
 
   return job_rfd;
+#endif
 }
 
 void
@@ -80,19 +90,21 @@ jobserver_parse_arg (const char* arg)
   DB (DB_JOBS,
       (_("Jobserver client (fds %d,%d)\n"), job_fds[0], job_fds[1]));
 
-#ifdef HAVE_FCNTL
-# define FD_OK(_f) ((fcntl ((_f), F_GETFD) != -1) || (errno != EBADF))
+#ifdef HAVE_FCNTL_H
+# define FD_OK(_f) (fcntl ((_f), F_GETFD) != -1)
 #else
 # define FD_OK(_f) 1
 #endif
 
-  /* Create a duplicate pipe, that will be closed in the SIGCHLD handler.  If
-     this fails with EBADF, the parent has closed the pipe on us because it
-     didn't think we were a submake.  If so, warn then default to -j1.  */
+  /* Make sure our pipeline is valid, and (possibly) create a duplicate pipe,
+     that will be closed in the SIGCHLD handler.  If this fails with EBADF,
+     the parent has closed the pipe on us because it didn't think we were a
+     submake.  If so, warn and default to -j1.  */
+
   if (!FD_OK (job_fds[0]) || !FD_OK (job_fds[1]) || make_job_rfd () < 0)
     {
       if (errno != EBADF)
-        pfatal_with_name (_("dup jobserver"));
+        pfatal_with_name (_("jobserver pipeline"));
 
       O (error, NILF,
          _("warning: jobserver unavailable: using -j1.  Add '+' to parent make rule."));
@@ -186,7 +198,85 @@ void jobserver_post_child ()
 #endif
 }
 
-/* The acquire algorithm goes like this (from job.c):
+void
+jobserver_signal ()
+{
+  if (job_rfd >= 0)
+    {
+      close (job_rfd);
+      job_rfd = -1;
+    }
+}
+
+void
+jobserver_pre_acquire ()
+{
+  /* Make sure we have a dup'd FD.  */
+  if (job_rfd < 0 && job_fds[0] >= 0 && make_job_rfd () < 0)
+    pfatal_with_name (_("duping jobs pipe"));
+}
+
+#ifdef HAVE_PSELECT
+
+/* Use pselect() to atomically wait for both a signal and a file descriptor.
+   It also provides a timeout facility so we don't need to use SIGALRM.
+
+   This method relies on the fact that SIGCHLD will be blocked everywhere,
+   and only unblocked (atomically) within the pselect() call, so we can
+   never miss a SIGCHLD.
+ */
+int
+jobserver_acquire (int timeout)
+{
+  sigset_t empty;
+  fd_set readfds;
+  struct timespec spec;
+  struct timespec *specp = NULL;
+  int r;
+  char intake;
+
+  sigemptyset (&empty);
+
+  FD_ZERO (&readfds);
+  FD_SET (job_fds[0], &readfds);
+
+  if (timeout)
+    {
+      /* Alarm after one second (is this too granular?)  */
+      spec.tv_sec = 1;
+      spec.tv_nsec = 0;
+      specp = &spec;
+    }
+
+  r = pselect (job_fds[0]+1, &readfds, NULL, NULL, specp, &empty);
+
+  if (r == -1)
+    {
+      /* Better be SIGCHLD.  */
+      if (errno != EINTR)
+        pfatal_with_name (_("pselect jobs pipe"));
+      return 0;
+    }
+
+  if (r == 0)
+    /* Timeout.  */
+    return 0;
+
+  /* The read FD is ready: read it!  */
+  EINTRLOOP (r, read (job_fds[0], &intake, 1));
+  if (r < 0)
+    pfatal_with_name (_("read jobs pipe"));
+
+  /* What does it mean if read() returns 0?  It shouldn't happen because only
+     the master make can reap all the tokens and close the write side...??  */
+  return r;
+}
+
+#else
+
+/* This method uses a "traditional" UNIX model for waiting on both a signal
+   and a file descriptor.  However, it's complex and since we have a SIGCHLD
+   handler installed we need to check ALL system calls for EINTR: painful!
 
    Read a token.  As long as there's no token available we'll block.  We
    enable interruptible system calls before the read(2) so that if we get a
@@ -264,28 +354,6 @@ set_child_handler_action_flags (int set_handler, int set_alarm)
 #endif
 }
 
-void
-jobserver_signal ()
-{
-  if (job_rfd >= 0)
-    {
-      close (job_rfd);
-      job_rfd = -1;
-    }
-}
-
-void
-jobserver_pre_acquire ()
-{
-  /* Make sure we have a dup'd FD.  */
-  if (job_rfd < 0 && job_fds[0] >= 0)
-    {
-      DB (DB_JOBS, ("Duplicate the job FD\n"));
-      if (make_job_rfd () < 0)
-        pfatal_with_name (_("duping jobs pipe"));
-    }
-}
-
 int
 jobserver_acquire (int timeout)
 {
@@ -317,4 +385,6 @@ jobserver_acquire (int timeout)
   return 0;
 }
 
+#endif
+
 #endif /* MAKE_JOBSERVER */