On Fri, 6 Sep 2024 18:01:08 +0900
Takashi Yano wrote:
> diff --git a/winsup/cygwin/select.cc b/winsup/cygwin/select.cc
> index bc02c3f9d..9ddb9898c 100644
> --- a/winsup/cygwin/select.cc
> +++ b/winsup/cygwin/select.cc
> @@ -642,7 +642,7 @@ pipe_data_available (int fd, fhandler_base *fh, HANDLE h,
> int flags)
> Consequentially, the only reliable information is available on the
> read side, so fetch info from the read side via the pipe-specific
> query handle. Use fpli.WriteQuotaAvailable as storage for the actual
> - interesting value, which is the InboundQuote on the write side,
> + interesting value, which is the IutboundQuota on the write side,
> decremented by the number of bytes of data in that buffer. */
> /* Note: Do not use NtQueryInformationFile() for query_hdl because
> NtQueryInformationFile() seems to interfere with reading pipes
> @@ -655,19 +655,17 @@ pipe_data_available (int fd, fhandler_base *fh, HANDLE
> h, int flags)
> handling this fact. */
> if (fh->get_device () == FH_PIPEW && fpli.WriteQuotaAvailable == 0)
> {
> - HANDLE query_hdl = ((fhandler_pipe *) fh)->get_query_handle ();
> - if (!query_hdl)
> - query_hdl = ((fhandler_pipe *) fh)->temporary_query_hdl ();
> - if (!query_hdl) /* We cannot know actual write pipe space. */
> - return (flags & PDA_SELECT) ? PIPE_BUF : 1;
> - DWORD nbytes_in_pipe;
> - BOOL res =
> - PeekNamedPipe (query_hdl, NULL, 0, NULL, &nbytes_in_pipe, NULL);
> - if (!((fhandler_pipe *) fh)->get_query_handle ())
> - CloseHandle (query_hdl); /* Close temporary query_hdl */
> - if (!res) /* We cannot know actual write pipe space. */
> - return (flags & PDA_SELECT) ? PIPE_BUF : 1;
> - fpli.WriteQuotaAvailable = fpli.InboundQuota - nbytes_in_pipe;
> + /* NtSetInformationFile() in set_pipe_non_blocking(true)
> + seems to fail for unknown reasons with STATUS_PIPE_BUSY
> + if no reader is reading the pipe. In this case, the pipe
> + is really full if WriteQuotaAvailable is zero. Otherwise,
> + the pipe is empty. */
> + if (!((fhandler_pipe *) fh)->set_pipe_non_blocking (true))
> + return 0; /* Full */
> + /* Restore pipe mode to blocking mode */
> + ((fhandler_pipe *) fh)->set_pipe_non_blocking (false);
> + /* Empty */
> + fpli.WriteQuotaAvailable = fpli.IutboundQuota;
^^^ In
Of cource...
> }
> if (fpli.WriteQuotaAvailable > 0)
> {
--
Takashi Yano <takashi.y...@nifty.ne.jp>
