Add logging to fairlock

Log to LOCAL2 at log level INFO when a lock is acquired and released,
and when the client holding the lock sends anything through the socket
(they can use this to identify themselves to the logging e.g. by sending
"PID <PID>"

Signed-off-by: Mark Syms <[email protected]>

misc/fairlock/fairlock.c

@@ -4,6 +4,7 @@
 #include <sys/socket.h>
 #include <sys/un.h>
 #include <errno.h>
+#include <syslog.h>
 
 int main(int argc, char *argv[]) {
      struct sockaddr_un addr;
@@ -31,6 +32,7 @@ int main(int argc, char *argv[]) {
         fprintf(stderr, "listen(64) failed on socket %s: %s", argv[1], strerror(errno));
         exit(1);
     }
+    openlog("fairlock", LOG_CONS | LOG_PID | LOG_NDELAY, LOG_LOCAL2);
 
     /* Now we have a socket, enter an endless loop of:
      * 1) Accept a connection
@@ -50,8 +52,14 @@ int main(int argc, char *argv[]) {
         while ((fd = accept(sock, NULL, NULL)) > -1) {
             char buffer[128];
 
-            do {} while (read(fd, buffer, sizeof(buffer)) > 0);
+            syslog(LOG_INFO, "%s acquired\n", argv[1]);
+            while (read(fd, buffer, sizeof(buffer)) > 0) {
+                buffer[127]='\0';
+                syslog(LOG_INFO, "%s sent '%s'\n", argv[1], buffer);
+            }
             close(fd);
+            syslog(LOG_INFO, "%s released\n", argv[1]);
         }
     }
+    closelog();
 }

misc/fairlock/fairlock.py

@@ -57,6 +57,8 @@ def __enter__(self):
         except (FileNotFoundError, ConnectionRefusedError):
             self._ensure_service()
             self.sock.connect(self.sockname)
+
+        self.sock.send(f'{os.getpid()} - {time.monotonic()}'.encode())
         self.connected = True
         return self