Implement get_nr_ts_release_waiters() /proc wrapper

Add a wrapper for /proc/litmus/stats to make it easy to query the
number of tasks already waiting for a task set release.

1 files changed, 39 insertions, 0 deletions

diff --git a/src/kernel_iface.c b/src/kernel_iface.c
index 33d56df..b9c8f59 100644
--- a/src/kernel_iface.c
+++ b/src/kernel_iface.c
@@ -12,6 +12,8 @@
 #define LITMUS_CTRL_DEVICE "/dev/litmus/ctrl"
 #define CTRL_PAGES 1
 
+#define LITMUS_STATS_FILE "/proc/litmus/stats"
+
 static int map_file(const char* filename, void **addr, size_t size)
 {
         int error = 0;
@@ -35,6 +37,43 @@ static int map_file(const char* filename, void **addr, size_t size)
         return error;
 }
 
+ssize_t read_file(const char* fname, void* buf, size_t maxlen)
+{
+        int fd;
+        ssize_t n = 0;
+        size_t got = 0;
+
+        fd = open(fname, O_RDONLY);
+        if (fd == -1)
+                return -1;
+
+        while (got < maxlen && (n = read(fd, buf + got, maxlen - got)) > 0)
+                got += n;
+        close(fd);
+        if (n < 0)
+                return -1;
+        else
+                return got;
+}
+
+int get_nr_ts_release_waiters(void)
+{
+        int ready = 0, all = 0;
+        char buf[100];
+        ssize_t len;
+
+        len = read_file(LITMUS_STATS_FILE, buf, sizeof(buf) - 1);
+        if (len >= 0)
+                len = sscanf(buf,
+                             "real-time tasks   = %d\n"
+                             "ready for release = %d\n",
+                             &all, &ready);
+        if (len == 2)
+                return ready;
+        else
+                return len;
+}
+
 /* thread-local pointer to control page */
 static __thread struct control_page *ctrl_page;