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.

4 files changed, 44 insertions, 19 deletions

diff --git a/bin/release_ts.c b/bin/release_ts.c
index 9740df2..7752097 100644
--- a/bin/release_ts.c
+++ b/bin/release_ts.c
@@ -7,6 +7,7 @@
 #include <fcntl.h>
 
 #include "litmus.h"
+#include "internal.h"
 
 #define OPTSTR "d:wf:"
 #define NS_PER_MS 1000000
@@ -27,25 +28,6 @@ void usage(char *error) {
         exit(1);
 }
 
-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;
-}
-
 void wait_until_ready(int expected)
 {
         int ready = 0, all = 0;
diff --git a/include/internal.h b/include/internal.h
index f30ce61..747f095 100644
--- a/include/internal.h
+++ b/include/internal.h
@@ -26,5 +26,8 @@ int __launch_rt_task(rt_fn_t rt_prog, void *rt_arg,
 #define BUILD_BUG_ON_ZERO(e) (sizeof(struct { int:-!!(e); }))
 #define BUILD_BUG_ON(condition) ((void)BUILD_BUG_ON_ZERO(condition))
 
+/* I/O convenience function */
+ssize_t read_file(const char* fname, void* buf, size_t maxlen);
+
 #endif
 
diff --git a/include/litmus.h b/include/litmus.h
index 82e4bd1..e4b619e 100644
--- a/include/litmus.h
+++ b/include/litmus.h
@@ -120,6 +120,7 @@ int  requested_to_preempt(void);
 /* task system support */
 int wait_for_ts_release(void);
 int release_ts(lt_t *delay);
+int get_nr_ts_release_waiters(void);
 
 #define __NS_PER_MS 1000000
 
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;