2012-05-08 cgf-000004 The change for cgf-000003 introduced a new problem: http://cygwin.com/ml/cygwin/2012-05/msg00154.html http://cygwin.com/ml/cygwin/2012-05/msg00157.html Since a handle associated with the parent is no longer being duplicated into a non-cygwin "execed child", Windows is free to reuse the pid of the parent when the parent exits. However, since we *did* duplicate a handle pointing to the pid's shared memory area into the "execed child", the shared memory for the pid was still active. Since the shared memory was still available, if a new process reuses the previous pid, Cygwin would detect that the shared memory was not created and had a "PID_REAPED" flag. That was considered an error, and, so, it would set procinfo to NULL and pinfo::thisproc would die since this situation is not supposed to occur. I fixed this in two ways: 1) If a shared memory region has a PID_REAPED flag then zero it and reuse it. This should be safe since you are not really supposed to be querying the shared memory region for anything after PID_REAPED has been set. 2) Forego duping a copy of myself_pinfo if we're starting a non-cygwin child for exec. It seems like 2) is a common theme and an audit of all of the handles that are being passed to non-cygwin children is in order for 1.7.16. The other minor modification that was made in this change was to add the pid of the failing process to fork error output. This helps slightly when looking at strace output, even though in this case it was easy to find what was failing by looking for '^---' when running the "stv" strace dumper. That found the offending exception quickly. 2012-05-07 cgf-000003 <1.7.15> Don't make Cygwin wait for all children of a non-cygwin child program. Fixes: http://cygwin.com/ml/cygwin/2012-05/msg00063.html, http://cygwin.com/ml/cygwin/2012-05/msg00075.html This problem is due to a recent change which added some robustness and speed to Cygwin's exec/spawn handling by not trying to force inheritance every time a process is started. See ChangeLog entries starting on 2012-03-20, and multiple on 2012-03-21. Making the handle inheritable meant that, as usual, there were problems with non-Cygwin processes. When Cygwin "execs" a non-Cygwin process N, all of its N + 1, N + 2, ... children will also inherit the handle. That means that Cygwin will wait until all subprocesses have exited before it returns. I was willing to make this a restriction of starting non-Cygwin processes but the problem with allowing that is that it can cause the creation of a "limbo" pid when N exits and N + 1 and friends are still around. In this scenario, Cygwin dutifully notices that process N has died and sets the exit code to indicate that but N's parent will wait on rd_proc_pipe and will only return when every N + ... windows process has exited. The removal of cygheap::pid_handle was not related to the initial problem that I set out to fix. The change came from the realization that we were duping the current process handle into the child twice and only needed to do it once. The current process handle is used by exec to keep the Windows pid "alive" so that it will not be reused. So, now we just close parent in child_info_spawn::handle_spawn iff we're not execing. In debugging this it bothered me that 'ps' identified a nonactive pid as active. Part of the reason for this was the 'parent' handle in child_info was opened in non-Cygwin processes, keeping the pid alive. That has been kluged around (more changes after 1.7.15) but that didn't fix the problem. On further investigation, this seems to be caused by the fact that the shared memory region pid handles were still being passed to non-cygwin children, keeping the pid alive in a limbo-like fashion. This was easily fixed by having pinfo::init() consider a memory region with PID_REAPED as not available. A more robust fix should be considered for 1.7.15+ where these handles are not passed to non-cygwin processes. This fixed the problem where a pid showed up in the list after a user does something like: "bash$ cmd /c start notepad" but, for some reason, it does not fix the problem where "bash$ setsid cmd /c start notepad". That bears investigation after 1.7.15 is released but it is not a regression and so is not a blocker for the release. 2012-05-03 cgf-000002 <1.7.15> Fix problem where too much input was attempted to be read from a pty slave. Fixes: http://cygwin.com/ml/cygwin/2012-05/msg00049.html My change on 2012/04/05 reintroduced the problem first described by: http://cygwin.com/ml/cygwin/2011-10/threads.html#00445 The problem then was, IIRC, due to the fact that bytes sent to the pty pipe were not written as records. Changing pipe to PIPE_TYPE_MESSAGE in pipe.cc fixed the problem since writing lines to one side of the pipe caused exactly that the number of characters to be read on the other even if there were more characters in the pipe. To debug this, I first replaced fhandler_tty.cc with the 1.258, 2012/04/05 version. The test case started working when I did that. So, then, I replaced individual functions, one at a time, in fhandler_tty.cc with their previous versions. I'd expected this to be a problem with fhandler_pty_master::process_slave_output since that had seen the most changes but was surprised to see that the culprit was fhandler_pty_slave::read(). The reason was that I really needed the bytes_available() function to return the number of bytes which would be read in the next operation rather than the number of bytes available in the pipe. That's because there may be a number of lines available to be read but the number of bytes which will be read by ReadFile should reflect the mode of the pty and, if there is a line to read, only the number of bytes in the line should be seen as available for the next read. Having bytes_available() return the number of bytes which would be read seemed to fix the problem but it could subtly change the behavior of other callers of this function. However, I actually think this is probably a good thing since they probably should have been seeing the line behavior. 2012-05-02 cgf-000001 <1.7.15> Fix problem setting parent pid to 1 when process with children execs itself. Fixes: http://cygwin.com/ml/cygwin/2012-05/msg00009.html Investigating this problem with strace showed that ssh-agent was checking the parent pid and getting a 1 when it shouldn't have. Other stuff looked ok so I chose to consider this a smoking gun. Going back to the version that the OP said did not have the problem, I worked forward until I found where the problem first occurred - somewhere around 2012-03-19. And, indeed, the getppid call returned the correct value in the working version. That means that this stopped working when I redid the way the process pipe was inherited around this time period. It isn't clear why (and I suspect I may have to debug this further at some point) this hasn't always been a problem but I made the obvious fix. We shouldn't have been setting ppid = 1 when we're about to pass off to an execed process. As I was writing this, I realized that it was necessary to add some additional checks. Just checking for "have_execed" isn't enough. If we've execed a non-cygwin process then it won't know how to deal with any inherited children. So, always set ppid = 1 if we've execed a non-cygwin process.