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Takashi Yano f79a46112e Cygwin: pipe: Use read pipe handle for select() on write pipe. 
- Usually WriteQuotaAvailable retrieved by NtQueryInformationFile()
  on the write side reflects the space available in the inbound buffer
  on the read side. However, if a pipe read is currently pending,
  WriteQuotaAvailable on the write side is decremented by the number
  of bytes the read side is requesting. So it's possible (even likely)
  that WriteQuotaAvailable is 0, even if the inbound buffer on the
  read side is not full. This can lead to a deadlock situation:
  The reader is waiting for data, but select on the writer side
  assumes that no space is available in the read side inbound buffer.

  Currently, to avoid this stuation, read() does not request larger
  block than pipe size - 1. However, this mechanism does not take
  effect if the reader side is non-cygwin app.

  The only reliable information is available on the read side, so
  fetch info from the read side via the pipe-specific query handle
  (query_hdl) introduced.

  If the query_hdl (read handle) is kept in write side, writer can
  not detect closure of read pipe. Therefore, raw_write() counts
  write handle and query_hdl. If they are equal, only the pairs of
  write handle and query_hdl are alive. In this case, raw_write()
  returns EPIPE and raises SIGPIPE.

- Nonblocking pipes (PIPE_NOWAIT) are not well handled by non-Cygwin
  tools, so convert pipe handles to PIPE_WAIT handles when spawning
  a non-Cygwin process.
 		2021-09-14 13:01:40 +02:00
..
CVSChangeLogs.old winsup: Move all old CVS Changelogs into CVSChangeLogs.old dir 2016-03-19 13:59:52 +01:00
cygserver Cygwin: Allow using CFLAGS also for C++ files 2021-08-26 22:21:53 +02:00
cygwin Cygwin: pipe: Use read pipe handle for select() on write pipe. 2021-09-14 13:01:40 +02:00
doc Cygwin: Make gmondump conform to its doc + adjust doc 2021-08-03 10:00:56 +02:00
testsuite Cygwin: testsuite: avoid "conflicting types" gcc warning 2021-09-03 12:15:53 +02:00
utils Cygwin: Allow using CFLAGS also for C++ files 2021-08-26 22:21:53 +02:00
CONTRIBUTORS Cygwin: Add Ben Wijen to list of contributors 2021-01-18 12:01:19 +01:00
COPYING
…
COPYING.LIB Switching the Cygwin DLL to LGPLv3+, dropping commercial buyout option 2016-06-23 10:09:17 +02:00
CYGWIN_LICENSE Clarify source file license in CYGWIN_LICENSE 2016-06-23 21:52:12 +02:00
Makefile.am Cygwin: Use automake (v5) 2021-04-27 16:49:56 +01:00
Makefile.am.common Cygwin: automake: change @INCLUDES@ to @AM_CPPFLAGS@ to avoid warnings 2021-04-29 11:28:14 +02:00
README Fix typo and wrong URL in winsup/README 2016-05-24 10:25:18 +02:00
acinclude.m4 Cygwin: automake: change @INCLUDES@ to @AM_CPPFLAGS@ to avoid warnings 2021-04-29 11:28:14 +02:00
autogen.sh Cygwin: autogen.sh: Allow running from any directory 2021-05-06 10:56:20 +02:00
configure.ac Cygwin: Use automake (v5) 2021-04-27 16:49:56 +01:00

README 

THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESSED OR
IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED
WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.

Cygwin documentation is available on the net at https://cygwin.com
You might especially be interested in

https://cygwin.com/faq/faq.html#faq.programming.building-cygwin