Fall back to kill() if the kernel doesn't support tkill().

server/ptrace.c

diff --git a/server/ptrace.c b/server/ptrace.c
index 5323007..dafa698 100644
--- a/server/ptrace.c
+++ b/server/ptrace.c
@@ -157,7 +157,11 @@
 
     if (thread->unix_pid != -1)
     {
-        if (thread->unix_tid != -1) ret = tkill( thread->unix_tid, sig );
+        if (thread->unix_tid != -1)
+        {
+            ret = tkill( thread->unix_tid, sig );
+            if (ret == -1 && errno == ENOSYS) ret = kill( thread->unix_pid, sig );
+        }
         else ret = kill( thread->unix_pid, sig );
 
         if (ret == -1 && errno == ESRCH) /* thread got killed */