Cygwin: FIFO: add a spinlock

Don't let listen_client_thread and raw_read access the client list
simultaneously.

diff --git a/winsup/cygwin/fhandler.h b/winsup/cygwin/fhandler.h
index e7c4af6a17970eba5fe75c44f09792b95e6b1714..997dc0b6deeb68114b7e2f55abfb05aacdac7e61 100644 (file)
--- a/winsup/cygwin/fhandler.h
+++ b/winsup/cygwin/fhandler.h
@@ -1267,6 +1267,7 @@ class fhandler_fifo: public fhandler_base
   WCHAR pipe_name_buf[CYGWIN_FIFO_PIPE_NAME_LEN + 1];
   fifo_client_handler client[MAX_CLIENTS];
   int nclients, nconnected;
+  af_unix_spinlock_t _fifo_client_lock;
   bool __reg2 wait (HANDLE);
   NTSTATUS npfs_handle (HANDLE &);
   HANDLE create_pipe_instance (bool);
@@ -1278,6 +1279,8 @@ public:
   fhandler_fifo ();
   PUNICODE_STRING get_pipe_name ();
   DWORD listen_client_thread ();
+  void fifo_client_lock () { _fifo_client_lock.lock (); }
+  void fifo_client_unlock () { _fifo_client_lock.unlock (); }
   int open (int, mode_t);
   off_t lseek (off_t offset, int whence);
   int close ();

diff --git a/winsup/cygwin/fhandler_fifo.cc b/winsup/cygwin/fhandler_fifo.cc
index e91e8805094ae128a3819927437ae9ba802176d7..b0016ee909045b76f557a990f90dc4bcc0fafe0f 100644 (file)
--- a/winsup/cygwin/fhandler_fifo.cc
+++ b/winsup/cygwin/fhandler_fifo.cc
@@ -349,13 +349,17 @@ fhandler_fifo::listen_client_thread ()
       int i;
       DWORD wait_ret;
 
+      fifo_client_lock ();
       found = false;
       for (i = 0; i < nclients; i++)
        switch (client[i].state)
          {
          case fc_invalid:
            if (disconnect_and_reconnect (i) < 0)
-             goto errout;
+             {
+               fifo_client_unlock ();
+               goto errout;
+             }
            /* Fall through. */
          case fc_connected:
            w[i] = client[i].dummy_evt;
@@ -369,13 +373,15 @@ fhandler_fifo::listen_client_thread ()
            break;
          }
       w[nclients] = lct_termination_evt;
+      int res = 0;
       if (!found)
-       {
-         if (add_client () < 0)
-           goto errout;
-         else
-           continue;
-       }
+       res = add_client ();
+      fifo_client_unlock ();
+      if (res < 0)
+       goto errout;
+      else if (!found)
+       continue;
+
       if (!arm (read_ready))
        {
          __seterrno ();
@@ -391,9 +397,11 @@ fhandler_fifo::listen_client_thread ()
        return 0;
       else
        {
+         fifo_client_lock ();
          client[i].state = fc_connected;
          nconnected++;
          set_pipe_non_blocking (client[i].fh->get_handle (), true);
+         fifo_client_unlock ();
          yield ();
        }
     }
@@ -664,6 +672,7 @@ fhandler_fifo::raw_read (void *in_ptr, size_t& len)
        }
 
       /* Poll the connected clients for input. */
+      fifo_client_lock ();
       for (int i = 0; i < nclients; i++)
        if (client[i].state == fc_connected)
          {
@@ -671,15 +680,22 @@ fhandler_fifo::raw_read (void *in_ptr, size_t& len)
            client[i].fh->fhandler_base::raw_read (in_ptr, len);
            ssize_t nread = (ssize_t) len;
            if (nread > 0)
-             return;
+             {
+               fifo_client_unlock ();
+               return;
+             }
            else if (nread < 0 && GetLastError () != ERROR_NO_DATA)
-             goto errout;
+             {
+               fifo_client_unlock ();
+               goto errout;
+             }
            else if (nread == 0) /* Client has disconnected. */
              {
                client[i].state = fc_invalid;
                nconnected--;
              }
          }
+      fifo_client_unlock ();
       if (is_nonblocking ())
        {
          set_errno (EAGAIN);