Hi Ken,
Do these patches enable to open FIFO multiple times with O_RDWR?
mc (midnight commander) tries to open FIFO twice with O_RDWR if
SHELL=/bin/tcsh, but fails.
https://cygwin.com/ml/cygwin/2017-03/msg00188.html
On Mon, 25 Mar 2019 23:06:10 +0000 Ken Brown wrote:
> If a FIFO is opened with O_RDWR access, create the pipe with
> read/write access, and make the first client have the handle of that
> pipe as its I/O handle.
>
> Adjust fhandler_fifo::raw_read to account for the result of trying to
> read from that client if there's no data.
> ---
> winsup/cygwin/fhandler.h | 5 +++
> winsup/cygwin/fhandler_fifo.cc | 79 +++++++++++++++++++++++++++++-----
> 2 files changed, 73 insertions(+), 11 deletions(-)
>
> diff --git a/winsup/cygwin/fhandler.h b/winsup/cygwin/fhandler.h
> index ef34f9c40..3398cc625 100644
> --- a/winsup/cygwin/fhandler.h
> +++ b/winsup/cygwin/fhandler.h
> @@ -1253,6 +1253,10 @@ struct fifo_client_handler
> HANDLE dummy_evt; /* Never signaled. */
> fifo_client_handler () : fh (NULL), state (fc_unknown), connect_evt (NULL),
> dummy_evt (NULL) {}
> + fifo_client_handler (fhandler_base *_fh, fifo_client_connect_state _state,
> + HANDLE _connect_evt, HANDLE _dummy_evt)
> + : fh (_fh), state (_state), connect_evt (_connect_evt),
> + dummy_evt (_dummy_evt) {}
> int connect ();
> int close ();
> };
> @@ -1268,6 +1272,7 @@ class fhandler_fifo: public fhandler_base
> fifo_client_handler client[MAX_CLIENTS];
> int nclients, nconnected;
> af_unix_spinlock_t _fifo_client_lock;
> + bool _duplexer;
> bool __reg2 wait (HANDLE);
> NTSTATUS npfs_handle (HANDLE &);
> HANDLE create_pipe_instance (bool);
> diff --git a/winsup/cygwin/fhandler_fifo.cc b/winsup/cygwin/fhandler_fifo.cc
> index 2c20444c6..7847cca82 100644
> --- a/winsup/cygwin/fhandler_fifo.cc
> +++ b/winsup/cygwin/fhandler_fifo.cc
> @@ -33,7 +33,7 @@ STATUS_PIPE_EMPTY simply means there's no data to be read.
> */
> fhandler_fifo::fhandler_fifo ():
> fhandler_base (), read_ready (NULL), write_ready (NULL),
> listen_client_thr (NULL), lct_termination_evt (NULL), nclients (0),
> - nconnected (0)
> + nconnected (0), _duplexer (false)
> {
> pipe_name_buf[0] = L'\0';
> need_fork_fixup (true);
> @@ -224,6 +224,8 @@ fhandler_fifo::create_pipe_instance (bool first)
> }
> access = GENERIC_READ | FILE_READ_ATTRIBUTES | FILE_WRITE_ATTRIBUTES
> | SYNCHRONIZE;
> + if (first && _duplexer)
> + access |= GENERIC_WRITE;
> sharing = FILE_SHARE_READ | FILE_SHARE_WRITE;
> hattr = OBJ_INHERIT;
> if (first)
> @@ -437,7 +439,7 @@ fhandler_fifo::open (int flags, mode_t)
> case O_RDWR:
> reader = true;
> writer = false;
> - duplexer = true;
> + duplexer = _duplexer = true;
> break;
> default:
> set_errno (EINVAL);
> @@ -447,7 +449,7 @@ fhandler_fifo::open (int flags, mode_t)
>
> debug_only_printf ("reader %d, writer %d, duplexer %d", reader, writer,
> duplexer);
> set_flags (flags);
> - if (reader)
> + if (reader && !duplexer)
> nohandle (true);
>
> /* Create control events for this named pipe */
> @@ -472,6 +474,48 @@ fhandler_fifo::open (int flags, mode_t)
> goto out;
> }
>
> + /* If we're a duplexer, create the pipe and the first client. */
> + if (duplexer)
> + {
> + HANDLE ph, connect_evt, dummy_evt;
> + fhandler_base *fh;
> +
> + ph = create_pipe_instance (true);
> + if (!ph)
> + {
> + res = error_errno_set;
> + goto out;
> + }
> + set_io_handle (ph);
> + set_pipe_non_blocking (ph, true);
> + if (!(fh = build_fh_dev (dev ())))
> + {
> + set_errno (EMFILE);
> + res = error_errno_set;
> + goto out;
> + }
> + fh->set_io_handle (ph);
> + fh->set_flags (flags);
> + if (!(connect_evt = create_event ()))
> + {
> + res = error_errno_set;
> + fh->close ();
> + delete fh;
> + goto out;
> + }
> + if (!(dummy_evt = create_event ()))
> + {
> + res = error_errno_set;
> + delete fh;
> + fh->close ();
> + CloseHandle (connect_evt);
> + goto out;
> + }
> + client[0] = fifo_client_handler (fh, fc_connected, connect_evt,
> + dummy_evt);
> + nconnected = nclients = 1;
> + }
> +
> /* If we're reading, start the listen_client thread (which should
> signal read_ready), and wait for a writer. */
> if (reader)
> @@ -482,8 +526,8 @@ fhandler_fifo::open (int flags, mode_t)
> res = error_errno_set;
> goto out;
> }
> - /* Wait for the listen_client thread to create the pipe and
> - signal read_ready. This should be quick. */
> + /* Wait for the listen_client thread to signal read_ready. This
> + should be quick. */
> HANDLE w[2] = { listen_client_thr, read_ready };
> switch (WaitForMultipleObjects (2, w, FALSE, INFINITE))
> {
> @@ -703,12 +747,25 @@ fhandler_fifo::raw_read (void *in_ptr, size_t& len)
> fifo_client_unlock ();
> return;
> }
> - else if (nread < 0 && GetLastError () != ERROR_NO_DATA)
> - {
> - fifo_client_unlock ();
> - goto errout;
> - }
> - else if (nread == 0) /* Client has disconnected. */
> + /* In the duplex case with no data, we seem to get nread
> + == -1 with ERROR_PIPE_LISTENING on the first attempt to
> + read from the duplex pipe (client[0]), and nread == 0
> + on subsequent attempts. */
> + else if (nread < 0)
> + switch (GetLastError ())
> + {
> + case ERROR_NO_DATA:
> + break;
> + case ERROR_PIPE_LISTENING:
> + if (_duplexer && i == 0)
> + break;
> + /* Fall through. */
> + default:
> + fifo_client_unlock ();
> + goto errout;
> + }
> + else if (nread == 0 && (!_duplexer || i > 0))
> + /* Client has disconnected. */
> {
> client[i].state = fc_invalid;
> nconnected--;
> --
> 2.17.0
>
--
Takashi Yano <takashi.y...@nifty.ne.jp>
