2012-05-14 cgf-000008 <1.7.16> - Fix hang when zero bytes are written to a pty using Windows WriteFile or equivalent. Fixes: http://cygwin.com/ml/cygwin/2012-05/msg00323.html cgf-000002, as usual, fixed one thing while breaking another. See Larry's predicament in: http://goo.gl/oGEr2 . The problem is that zero byte writes to the pty pipe caused the dread end-of-the-world-as-we-know-it problem reported on the mailing list where ReadFile reads zero bytes even though there is still more to read on the pipe. This is because that change caused a 'record' to be read and a record can be zero bytes. I was never really keen about using a throwaway buffer just to get a count of the number of characters available to be read in the pty pipe. On closer reading of the documentation for PeekNamedPipe it seemed like the sixth argument to PeekNamedPipe should return what I needed without using a buffer. And, amazingly, it did, except that the problem still remained - a zero byte message still screwed things up. So, we now detect the case where there is zero bytes available as a message but there are bytes available in the pipe. In that scenario, return the bytes available in the pipe rather than the message length of zero. This could conceivably cause problems with pty pipe handling in this scenario but since the only way this scenario could possibly happen is when someone is writing zero bytes using WriteFile to a pty pipe, I'm ok with that. 2012-05-14 cgf-000007 <1.7.16> - Fix invocation of strace from a cygwin process. Fixes: http://cygwin.com/ml/cygwin/2012-05/msg00292.html The change in cgf-000004 introduced a problem for processes which load cygwin1.dll dynamically. strace.exe is the most prominent example of this. Since the parent handle is now closed for "non-Cygwin" processes, when strace.exe tried to dynamically load cygwin1.dll, the handle was invalid and child_info_spawn::handle_spawn couldn't use retrieve information from the parent. This eventually led to a strace_printf error due to an attempt to dereference an unavailable cygheap. Probably have to fix this someday. You shouldn't use the cygheap while attempting to print an error about the inavailability of said cygheap. This was fixed by saving the parent pid in child_info_spawn and calling OpenProcess for the parent pid and using that handle iff a process is dynamically loaded. 2012-05-12 cgf-000006 <1.7.16> - Fix hang when calling pthread_testcancel in a canceled thread. Fixes some of: http://cygwin.com/ml/cygwin/2012-05/msg00186.html This should fix the first part of the reported problem in the above message. The cancel seemed to actually be working but, the fprintf eventually ended up calling pthread_testcancel. Since we'd gotten here via a cancel, it tried to recursively call the cancel handler causing a recursive loop. 2012-05-12 cgf-000005 <1.7.16> - Fix pipe creation problem which manifested as a problem creating a fifo. Fixes: http://cygwin.com/ml/cygwin/2012-05/msg00253.html My change on 2012-04-28 introduced a problem with fifos. The passed in name was overwritten. This was because I wasn't properly keeping track of the length of the generated pipe name when there was a name passed in to fhandler_pipe::create. There was also another problem in fhandler_pipe::create. Since fifos use PIPE_ACCESS_DUPLEX and PIPE_ACCESS_DUPLEX is an or'ing of PIPE_ACCESS_INBOUND and PIPE_ACCESS_OUTBOUND, using PIPE_ACCESS_OUTBOUND as a "never-used" option for PIPE_ADD_PID in fhandler.h was wrong. So, fifo creation attempted to add the pid of a pipe to the name which is wrong for fifos. 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.