diff --git a/src/cgproxyd.hpp b/src/cgproxyd.hpp
index 6214de5..25f0694 100644
--- a/src/cgproxyd.hpp
+++ b/src/cgproxyd.hpp
@@ -92,15 +92,19 @@ class cgproxyd {
 
     v = config.program_noproxy;
     if (find(v.begin(), v.end(), path) != v.end()) {
-      info("execsnoop noproxy: %d %s", pid, path);
-      free(path);
-      return attach(pid, config.cgroup_noproxy_preserved);
+      if (CGROUP::getCgroup(pid) != config.cgroup_noproxy_preserved) {
+        info("execsnoop noproxy: %d %s", pid, path);
+        free(path);
+        return attach(pid, config.cgroup_noproxy_preserved);
+      }
     }
     v = config.program_proxy;
     if (find(v.begin(), v.end(), path) != v.end()) {
-      info("execsnoop proxied: %d %s", pid, path);
-      free(path);
-      return attach(pid, config.cgroup_proxy_preserved);
+      if (CGROUP::getCgroup(pid) != config.cgroup_proxy_preserved) {
+        info("execsnoop proxied: %d %s", pid, path);
+        free(path);
+        return attach(pid, config.cgroup_proxy_preserved);
+      }
     }
     free(path);
     return 0;
@@ -208,16 +212,20 @@ class cgproxyd {
   }
 
   void processRunningProgram() {
-    debug("process running program") for (auto &path :
-                                          config.program_noproxy) for (auto &pid :
-                                                                       bash_pidof(path)) {
-      int status = attach(pid, config.cgroup_noproxy_preserved);
-      if (status == 0) info("noproxy running process %d %s", pid, path.c_str());
-    }
+    debug("process running program");
+    for (auto &path : config.program_noproxy)
+      for (auto &pid : bash_pidof(path)) {
+        if (CGROUP::getCgroup(pid) != config.cgroup_noproxy_preserved) {
+          int status = attach(pid, config.cgroup_noproxy_preserved);
+          if (status == 0) info("noproxy running process %d %s", pid, path.c_str());
+        }
+      }
     for (auto &path : config.program_proxy)
       for (auto &pid : bash_pidof(path)) {
-        int status = attach(pid, config.cgroup_proxy_preserved);
-        if (status == 0) info("proxied running process %d %s", pid, path.c_str());
+        if (CGROUP::getCgroup(pid) != config.cgroup_proxy_preserved) {
+          int status = attach(pid, config.cgroup_proxy_preserved);
+          if (status == 0) info("proxied running process %d %s", pid, path.c_str());
+        }
       }
   }
 
@@ -302,4 +310,4 @@ int main(int argc, char *argv[]) {
   return d.start();
 }
 } // namespace CGPROXY::CGPROXYD
-#endif
\ No newline at end of file
+#endif
diff --git a/src/cgroup_attach.cpp b/src/cgroup_attach.cpp
index 09b0e0a..1f64169 100644
--- a/src/cgroup_attach.cpp
+++ b/src/cgroup_attach.cpp
@@ -15,12 +15,6 @@ namespace CGPROXY::CGROUP {
 
 string cgroup2_mount_point = get_cgroup2_mount_point();
 
-bool exist(string path) {
-  struct stat st;
-  if (stat(path.c_str(), &st) != -1) { return S_ISDIR(st.st_mode); }
-  return false;
-}
-
 string get_cgroup2_mount_point() {
   stringstream buffer;
   FILE *fp = popen("findmnt -t cgroup2 -n -o TARGET", "r");
@@ -33,6 +27,24 @@ string get_cgroup2_mount_point() {
   return s;
 }
 
+string getCgroup(const pid_t &pid) { return getCgroup(to_str(pid)); }
+
+string getCgroup(const string &pid) {
+  string cgroup_f = to_str("/proc/", pid, "/cgroup");
+  if (!fileExist(cgroup_f)) return "";
+  char buf[128];
+  FILE *f = fopen(cgroup_f.c_str(), "r");
+  int id;
+  char cgroup[256];
+  while (fgets(buf, 128, f) != NULL) {
+    if (buf[0] == '0') {
+      if (sscanf(buf, "%*i::%s", cgroup) == 1) return cgroup;
+      error("sscanf %s failed", buf);
+    }
+  }
+  return "";
+}
+
 bool validate(string pid, string cgroup) {
   bool pid_v = validPid(pid);
   bool cg_v = validCgroup(cgroup);
@@ -50,14 +62,13 @@ int attach(const string pid, const string cgroup_target) {
 
   debug("attaching %s to %s", pid.c_str(), cgroup_target.c_str());
 
-  int status;
   if (!validate(pid, cgroup_target)) return_error;
   if (cgroup2_mount_point.empty()) return_error;
   string cgroup_target_path = cgroup2_mount_point + cgroup_target;
   string cgroup_target_procs = cgroup_target_path + "/cgroup.procs";
 
   // check if exist, we will create it if not exist
-  if (!exist(cgroup_target_path)) {
+  if (!dirExist(cgroup_target_path)) {
     if (mkdir(cgroup_target_path.c_str(),
               S_IRWXU | S_IRGRP | S_IXGRP | S_IROTH | S_IXOTH) == 0) {
       debug("created cgroup %s success", cgroup_target.c_str());
@@ -69,6 +80,11 @@ int attach(const string pid, const string cgroup_target) {
     // return_error
   }
 
+  if (getCgroup(pid) == cgroup_target) {
+    debug("%s already in %s", pid.c_str(), cgroup_target.c_str());
+    return_success;
+  }
+
   // put pid to target cgroup
   ofstream procs(cgroup_target_procs, ofstream::app);
   if (!procs.is_open()) {
@@ -91,4 +107,4 @@ int attach(const int pid, const string cgroup_target) {
   return attach(to_str(pid), cgroup_target);
 }
 
-} // namespace CGPROXY::CGROUP
\ No newline at end of file
+} // namespace CGPROXY::CGROUP
diff --git a/src/cgroup_attach.h b/src/cgroup_attach.h
index 62560db..34f81be 100644
--- a/src/cgroup_attach.h
+++ b/src/cgroup_attach.h
@@ -7,12 +7,13 @@ using namespace std;
 
 namespace CGPROXY::CGROUP {
 extern string cgroup2_mount_point;
-bool exist(string path);
 bool validate(string pid, string cgroup);
 string get_cgroup2_mount_point();
+string getCgroup(const pid_t &pid);
+string getCgroup(const string &pid);
 int attach(const string pid, const string cgroup_target);
 int attach(const int pid, const string cgroup_target);
 
 } // namespace CGPROXY::CGROUP
 
-#endif
\ No newline at end of file
+#endif