From: Christian Grothoff <christian@grothoff.org>
Date: Mon, 19 Oct 2009 09:35:56 +0000 (+0000)
Subject: use vfork if available, otherwise sleep after fork to avoid racing on signalling... 
X-Git-Tag: initial-import-from-subversion-38251~23333
X-Git-Url: https://git.librecmc.org/?a=commitdiff_plain;h=9a2a597e65ef4ee81df909d4c56377f51087001e;p=oweals%2Fgnunet.git

use vfork if available, otherwise sleep after fork to avoid racing on signalling the process vs execvp changing the signal handlers; clone without signal-handlers would also do, but is even less portable
---

diff --git a/src/include/platform.h b/src/include/platform.h
index 257fc7c6b..3393807f5 100644
--- a/src/include/platform.h
+++ b/src/include/platform.h
@@ -151,6 +151,10 @@
 #include <errno.h>
 #include <limits.h>
 
+#if HAVE_VFORK_H
+#include <vfork.h>
+#endif
+
 #if HAVE_CTYPE_H
 #include <ctype.h>
 #endif
diff --git a/src/util/os_priority.c b/src/util/os_priority.c
index 38f431251..4c77704bf 100644
--- a/src/util/os_priority.c
+++ b/src/util/os_priority.c
@@ -116,7 +116,6 @@ GNUNET_OS_set_process_priority (pid_t proc,
 }
 
 
-
 /**
  * Start a process.
  *
@@ -134,11 +133,31 @@ GNUNET_OS_start_process (const char *filename, ...)
   char **argv;
   int argc;
 
+#if HAVE_WORKING_VFORK
+  ret = vfork ();
+#else
   ret = fork ();
+#endif
   if (ret != 0)
     {
       if (ret == -1)
-        GNUNET_log_strerror (GNUNET_ERROR_TYPE_ERROR, "fork");
+	{
+	  GNUNET_log_strerror (GNUNET_ERROR_TYPE_ERROR, "fork");
+	}
+      else
+	{
+#if HAVE_WORKING_VFORK
+	  /* let's hope vfork actually works; for some extreme cases (including
+	     a testcase) we need 'execvp' to have run before we return, since
+	     we may send a signal to the process next and we don't want it
+	     to be caught by OUR signal handler (but either by the default
+	     handler or the actual handler as installed by the process itself). */
+#else
+	  /* let's give the child process a chance to run execvp, 1s should
+	     be plenty in practice */
+	  sleep (1);
+#endif
+	}
       return ret;
     }
   argc = 0;
@@ -154,7 +173,7 @@ GNUNET_OS_start_process (const char *filename, ...)
   va_end (ap);
   execvp (filename, argv);
   GNUNET_log_strerror_file (GNUNET_ERROR_TYPE_ERROR, "execvp", filename);
-  exit (1);
+  _exit (1);
 #else
   char *arg;
   unsigned int cmdlen;
@@ -209,16 +228,36 @@ GNUNET_OS_start_process_v (const char *filename, char *const argv[])
 #ifndef MINGW
   pid_t ret;
 
+#if HAVE_WORKING_VFORK
+  ret = vfork ();
+#else
   ret = fork ();
+#endif
   if (ret != 0)
     {
       if (ret == -1)
-        GNUNET_log_strerror (GNUNET_ERROR_TYPE_ERROR, "fork");
+	{
+	  GNUNET_log_strerror (GNUNET_ERROR_TYPE_ERROR, "fork");
+	}
+      else
+	{
+#if HAVE_WORKING_VFORK
+	  /* let's hope vfork actually works; for some extreme cases (including
+	     a testcase) we need 'execvp' to have run before we return, since
+	     we may send a signal to the process next and we don't want it
+	     to be caught by OUR signal handler (but either by the default
+	     handler or the actual handler as installed by the process itself). */
+#else
+	  /* let's give the child process a chance to run execvp, 1s should
+	     be plenty in practice */
+	  sleep (1);
+#endif
+	}
       return ret;
     }
   execvp (filename, argv);
   GNUNET_log_strerror_file (GNUNET_ERROR_TYPE_ERROR, "execvp", filename);
-  exit (1);
+  _exit (1);
 #else
   char **arg;
   unsigned int cmdlen;