Changeset 23869 in vbox

Timestamp:

Oct 19, 2009 2:32:57 PM (15 years ago)

Author:

vboxsync

Message:

fix/hack waitpid issues for unix platforms: racing of RT and xpcom, make waitpid for terminated child processes

Location:

trunk/src

Files:

• VBox/Runtime/r3/init.cpp (modified) (3 diffs)
• VBox/Runtime/r3/posix/process-posix.cpp (modified) (3 diffs)
• libs/xpcom18a4/nsprpub/pr/src/md/unix/uxproces.c (modified) (2 diffs)

trunk/src/VBox/Runtime/r3/init.cpp

@@ -42 +42 @@
 # ifndef RT_OS_OS2
 #  include <pthread.h>
+#  include <signal.h>
+#  include <errno.h>
+#  define IPRT_USE_SIG_CHILD_DUMMY
 # endif
 #endif
@@ -204 +207 @@
 }
 
+
+#ifdef IPRT_USE_SIG_CHILD_DUMMY
+/**
+ * Dummy SIGCHILD handler.
+ *
+ * Assigned on rtR3Init only when SIGCHILD handler is set SIGIGN or SIGDEF to
+ * ensure waitpid works properly for the terminated processes.
+ */
+static void rtR3SigChildHandler(int iSignal)
+{
+    NOREF(iSignal);
+}
+#endif /* IPRT_USE_SIG_CHILD_DUMMY */
+
+
 /**
  * rtR3Init worker.
@@ -296 +314 @@
     atexit(rtR3ExitCallback);
 
+#ifdef IPRT_USE_SIG_CHILD_DUMMY
+    /*
+     * SIGCHLD must not be ignored (that's default), otherwise posix compliant waitpid
+     * implementations won't work right.
+     */
+    for (;;)
+    {
+        struct sigaction saOld;
+        rc = sigaction(SIGCHLD, 0, &saOld);         AssertMsg(rc == 0, ("%d/%d\n", rc, errno));
+        if (    rc != 0
+            ||  (saOld.sa_flags & SA_SIGINFO)
+            || (   saOld.sa_handler != SIG_IGN
+                && saOld.sa_handler != SIG_DFL)
+           )
+            break;
+
+        /* Try install dummy handler. */
+        struct sigaction saNew = saOld;
+        saNew.sa_flags   = SA_NOCLDSTOP | SA_RESTART;
+        saNew.sa_handler = rtR3SigChildHandler;
+        rc = sigemptyset(&saNew.sa_mask);           AssertMsg(rc == 0, ("%d/%d\n", rc, errno));
+        struct sigaction saOld2;
+        rc = sigaction(SIGCHLD, &saNew, &saOld2);   AssertMsg(rc == 0, ("%d/%d\n", rc, errno));
+        if (    rc != 0
+            ||  (   saOld2.sa_handler == saOld.sa_handler
+                 && saOld2.sa_flags == saOld.sa_flags)
+           )
+            break;
+
+        /* Race during dynamic load, restore and try again... */
+        sigaction(SIGCHLD, &saOld2, NULL);
+        RTThreadYield();
+    }
+#endif /* IPRT_USE_SIG_CHILD_DUMMY */
+
 #ifdef IPRT_WITH_ALIGNMENT_CHECKS
     /*

trunk/src/VBox/Runtime/r3/posix/process-posix.cpp

@@ -110 +110 @@
     /*
      * Spawn the child.
+     *
+     * HACK ALERT! Put the process into a new process group with pgid = pid
+     * to make sure it differs from that of the parent process to ensure that
+     * the IPRT waipit call doesn't race anyone (read XPCOM) doing group wide
+     * waits.
      */
     pid_t pid;
@@ -115 +120 @@
     if (!(fFlags & RTPROC_FLAGS_DAEMONIZE))
     {
-        /** @todo check if it requires any of those two attributes, don't remember atm. */
-        rc = posix_spawn(&pid, pszExec, NULL, NULL, (char * const *)papszArgs,
-                         (char * const *)papszEnv);
+        posix_spawnattr_t Attr;
+
+        rc = posix_spawnattr_init(&Attr);
         if (!rc)
         {
-            if (pProcess)
-                *pProcess = pid;
-            return VINF_SUCCESS;
+# ifndef RT_OS_OS2 /* We don't need this on OS/2 and I don't recall if it's actually implemented. */
+            rc = posix_spawnattr_setflags(&Attr, POSIX_SPAWN_SETPGROUP);
+            Assert(rc == 0);
+            if (!rc)
+            {
+                rc = posix_spawnattr_setpgroup(&Attr, 0 /* pg == child pid */);
+                Assert(rc == 0);
+            }
+# endif
+            if (!rc)
+            {
+                /** @todo check if it requires any mandatory attributes or something, don't
+                 *        remember atm. */
+                rc = posix_spawn(&pid, pszExec, NULL, &Attr, (char * const *)papszArgs,
+                                 (char * const *)papszEnv);
+                if (!rc)
+                {
+                    int rc2 = posix_spawnattr_destroy(&Attr); Assert(rc2 == 0); NOREF(rc2);
+                    if (pProcess)
+                        *pProcess = pid;
+                    return VINF_SUCCESS;
+                }
+            }
+            int rc2 = posix_spawnattr_destroy(&Attr); Assert(rc2 == 0); NOREF(rc2);
         }
     }
@@ -131 +157 @@
         if (!pid)
         {
+            setpgid(0, 0); /* see comment above */
+
             if (fFlags & RTPROC_FLAGS_DAEMONIZE)
             {

trunk/src/libs/xpcom18a4/nsprpub/pr/src/md/unix/uxproces.c

@@ -674 +674 @@
         while (1) {
             do {
+#ifdef VBOX
+                /*
+                 * make sure we wait only for child of our group
+                 * to ensure we do not interfere with RT
+                 */
+                pid = waitpid((pid_t) 0, &status, 0);
+#else
                 pid = waitpid((pid_t) -1, &status, 0);
+#endif
             } while ((pid_t) -1 == pid && EINTR == errno);
 
@@ -764 +772 @@
         while (1) {
             do {
+#ifdef VBOX
+                /*
+                 * make sure we wait only for child of our group
+                 * to ensure we do not interfere with RT
+                 */
+                pid = waitpid((pid_t) 0, &status, WNOHANG);
+#else
                 pid = waitpid((pid_t) -1, &status, WNOHANG);
+#endif
             } while ((pid_t) -1 == pid && EINTR == errno);
             if (0 == pid) break;