Repeat sysctl in case of failures; increase the proc info buffer a bi…

…t to hold some more very recent procs

src/java.base/macosx/native/libjava/ProcessHandleImpl_macosx.c

@@ -97,23 +97,33 @@ jint os_getChildren(JNIEnv *env, jlong jpid, jlongArray jarray,
         }
     }
 
-    // Get buffer size needed to read all processes
-    int mib[4] = {CTL_KERN, KERN_PROC, KERN_PROC_ALL, 0};
-    if (sysctl(mib, 4, NULL, &bufSize, NULL, 0) < 0) {
-        JNU_ThrowByNameWithMessageAndLastError(env,
-            "java/lang/RuntimeException", "sysctl failed");
-        return -1;
-    }
+    int errsysctl;
+    int maxRetries = 100;
+    void *buffer = NULL;
+    do {
+        int mib[4] = {CTL_KERN, KERN_PROC, KERN_PROC_ALL, 0};
+        if (buffer != NULL) free(buffer);
+        // Get buffer size needed to read all processes
+        if (sysctl(mib, 4, NULL, &bufSize, NULL, 0) < 0) {
+            JNU_ThrowByNameWithMessageAndLastError(env,
+                "java/lang/RuntimeException", "sysctl failed");
+            return -1;
+        }
 
-    // Allocate buffer big enough for all processes
-    void *buffer = malloc(bufSize);
-    if (buffer == NULL) {
-        JNU_ThrowOutOfMemoryError(env, "malloc failed");
-        return -1;
-    }
+        // Allocate buffer big enough for all processes; add a little
+        // bit of space to be able to hold a few more proc infos
+        // for processes started rigth after the first sysctl call
+        buffer = malloc(bufSize + 4 * sizeof(struct kinfo_proc));
+        if (buffer == NULL) {
+            JNU_ThrowOutOfMemoryError(env, "malloc failed");
+            return -1;
+        }
+
+        // Read process info for all processes
+        errsysctl = sysctl(mib, 4, buffer, &bufSize, NULL, 0);
+    } while (errsysctl < 0 && maxRetries-- > 0);
 
-    // Read process info for all processes
-    if (sysctl(mib, 4, buffer, &bufSize, NULL, 0) < 0) {
+    if (errsysctl < 0) {
         JNU_ThrowByNameWithMessageAndLastError(env,
             "java/lang/RuntimeException", "sysctl failed to get info about all processes");
         free(buffer);