Fix previous commit

diff --git a/mono/utils/mono-proclib.c b/mono/utils/mono-proclib.c
index e8646ab6d0c8fac587bae96abaa64e7a7f3901a4..09f58bc04b2934b087ac97edba825d4898b411f7 100644 (file)
--- a/mono/utils/mono-proclib.c
+++ b/mono/utils/mono-proclib.c
@@ -510,13 +510,19 @@ mono_cpu_count (void)
         * means the normal way to query cpu count returns a wrong value with userspace API.
         * Instead we use /sys entries to query the actual hardware CPU count.
         */
-       char buffer[10] = {'\0'};
-       FILE* present = fopen ("/sys/devices/system/cpu/present", "r");
-       if (present != NULL && fread ((char*)buffer, 1, sizeof (buffer), present) > 3) {
-               count = atoi (((char*)buffer) + 2) + 1;
-               if (count > 0)
-                       return count;
-       }
+       char buffer[8] = {'\0'};
+       int present = open ("/sys/devices/system/cpu/present", O_RDONLY);
+       /* Format of the /sys entry is a cpulist of indexes which in the case
+        * of present is always of the form "0-(n-1)" when there is more than
+        * 1 core, n being the number of CPU cores in the system. Otherwise
+        * the value is simply 0
+        */
+       if (present != -1 && read (present, (char*)buffer, sizeof (buffer)) > 3)
+               count = strtol (((char*)buffer) + 2, NULL, 10);
+       if (present != -1)
+               close (present);
+       if (count > 0)
+               return count + 1;
 #endif
 #ifdef _SC_NPROCESSORS_ONLN
        count = sysconf (_SC_NPROCESSORS_ONLN);