Ar an deichiú lá de mí na Nollaig, scríobh Johann 'Myrkraverk' Oskarsson: I’ve gone ahead and applied that to 21.5. I have occasionally got hangs especially when VM is using an external program for qp-decoding, and I suspect your issue is at the root of them. I don’t see any downside to your change, XEmacs code further up the call stack needs to be able to handle smaller reads anyway. Thank you! APPROVE COMMIT NOTE: This patch has been committed # HG changeset patch # User Aidan Kehoe <kehoea(a)parhasard.net&gt; # Date 1513067231 0 # Tue Dec 12 08:27:11 2017 +0000 # Node ID affc195870d60c7f3f61d304cc01f205f63432d8 # Parent 0f7f0274157b50c71683368d0614b8912e2b70d7 Set input FDs to non-blocking unconditionally, thank you Myrkraverk src/ChangeLog addition: 2017-12-12 Aidan Kehoe <kehoea(a)parhasard.net&gt; * process-unix.c (unix_init_process_io_handles): Set input FDs to non-blocking unconditionally, see recent patch posted to xemacs-beta from Johann "Myrkraverk" Oskarsson. diff -r 0f7f0274157b -r affc195870d6 src/ChangeLog --- a/src/ChangeLog Wed Dec 06 20:52:28 2017 +0000 +++ b/src/ChangeLog Tue Dec 12 08:27:11 2017 +0000 ＠＠ -1,3 +1,9 ＠＠ +2017-12-12 Aidan Kehoe <kehoea(a)parhasard.net&gt; + + * process-unix.c (unix_init_process_io_handles): + Set input FDs to non-blocking unconditionally, see recent patch + posted to xemacs-beta from Johann "Myrkraverk" Oskarsson. + 2017-12-02 Aidan Kehoe <kehoea(a)parhasard.net&gt; * bytecode.c (set_compiled_function_arglist): diff -r 0f7f0274157b -r affc195870d6 src/process-unix.c --- a/src/process-unix.c Wed Dec 06 20:52:28 2017 +0000 +++ b/src/process-unix.c Tue Dec 12 08:27:11 2017 +0000 ＠＠ -831,6 +831,25 ＠＠ /* if sizeof(EMACS_INT) > sizeof(int) this truncates the value */ UNIX_DATA(p)->infd = (EMACS_INT) in; UNIX_DATA(p)->errfd = (EMACS_INT) err; + + /* In the event where the input file descriptor is a pipe, XEmacs as of + * 21.4.24 will hang on the read() system call when the pipe doesn't + * have enough to fill the incoming buffer. + * + * This will likely affect other kinds of blocking file descriptors also, so + * we unconditionally set the input fd to non-blocking mode. See: + * http://mid.xemacs.org/CAA_SOw__WYNiUO=4hHhiwg0LXq7++9Xr=tnBMgN5Uc8iAa+mvg... + * and the related thread. + */ + { + int f = fcntl (UNIX_DATA(p)->infd, F_SETFL, O_NONBLOCK); + if (f == -1) + { + warn_when_safe (Qio_error, lisp_strerror (errno), + "failed setting pipe (fd %ld) to nonblocking mode", + (EMACS_INT) in); + } + } } /* Move the file descriptor FD so that its number is not less than MIN. * -- ‘As I sat looking up at the Guinness ad, I could never figure out / How your man stayed up on the surfboard after forty pints of stout’ (C. Moore)