[R-gregmisc-users] SF.net SVN: r-gregmisc: [1053] trunk/fork

[<wa...@us...>]

Revision: 1053
          http://svn.sourceforge.net/r-gregmisc/?rev=1053&view=rev
Author:   warnes
Date:     2007-02-14 14:48:47 -0800 (Wed, 14 Feb 2007)

Log Message:
-----------
Add code to install SIGCHLD handler to avoid forked children from becoming zombies

Added Paths:
-----------
    trunk/fork/src/sigchld_handler.c
    trunk/fork/tests/
    trunk/fork/tests/test_many_fork.R

Added: trunk/fork/src/sigchld_handler.c
===================================================================
--- trunk/fork/src/sigchld_handler.c	                        (rev 0)
+++ trunk/fork/src/sigchld_handler.c	2007-02-14 22:48:47 UTC (rev 1053)
@@ -0,0 +1,73 @@
+#include <R.h>
+#include <Rdefines.h>
+
+/*
+  Code taken from a posting to the Gimp-developer mailing list by
+  Raphael Quinet quinet at gamers.org accessible at:
+  http://lists.xcf.berkeley.edu/lists/gimp-developer/2000-November/013572.html
+*/
+
+#include <signal.h>
+#include <sys/types.h>
+#include <sys/wait.h>
+#include <unistd.h>
+
+int installed=0;      // Has our sigcld signal hander already been installed?
+
+struct sigaction sa ; // our sigcld signal handler
+struct sigaction osa; // original (R) signal hander
+
+void sigchld_hander(int dummy) 
+{
+  int st;
+  while (wait3(&st, WNOHANG, NULL) > 0);
+}
+
+
+void R_install_sigcld_handler()
+{
+  int ret;
+
+  if(installed==0)
+    {
+      Rprintf ("Installing SIGCHLD signal handler...");
+      //sa.sa_handler = sigchld_handler;
+      sa.sa_handler = waiter;
+      //sigfillset (&sa.sa_mask);
+      //sa.sa_flags = SA_RESTART;
+      ret = sigaction (SIGCHLD, &sa, &osa);
+      if (ret < 0)
+	{
+	  error("Cannot set signal handler");
+	}
+      installed=-1;
+      Rprintf("Done.\n");
+    }
+  else
+    {
+      warning("SIGCLD signal handler already installed");
+    }
+
+}
+
+void R_restore_sigcld_handler()
+{
+  int ret;
+
+  if(installed==-1)
+    {
+      Rprintf ("Restoring original SIGCHLD signal handler...");
+      ret = sigaction (SIGCHLD, &osa, &sa);
+      if (ret < 0)
+	{
+	  error("Cannot reset signal handler");
+	}
+      installed=0;
+      Rprintf("Done.\n");
+    }
+  else
+    {
+      warning("SIGCLD signal handler not installed: cannot reset.");
+    }
+
+}

Added: trunk/fork/tests/test_many_fork.R
===================================================================
--- trunk/fork/tests/test_many_fork.R	                        (rev 0)
+++ trunk/fork/tests/test_many_fork.R	2007-02-14 22:48:47 UTC (rev 1053)
@@ -0,0 +1,20 @@
+library(fork)
+
+# ignore sigchld signals so child processes will die cleanly
+#signal("SIGCHLD","ignore")
+
+# start signal handler
+.C("R_install_sigcld_handler")
+
+for(i in 1:100)
+  {
+    pid = fork(slave=NULL) 
+    if(pid==0) { 
+      cat("Hi from the child process\n"); exit() 
+    } else {
+      cat("Hi from the parent process\n");
+    } 
+  }
+
+# remove signal handler
+.C("R_restore_sigcld_handler")


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