On Sun, Jan 16, 2022 at 5:36 PM Magnus Hagander <mag...@hagander.net> wrote: > > On Sun, Jan 16, 2022 at 5:34 PM Tom Lane <t...@sss.pgh.pa.us> wrote: > > > > Andres Freund <and...@anarazel.de> writes: > > > I don't immediately see a solution for this, other than to add > > > StreamCtl->stop_event (mirroring ->stop_socket) and then convert > > > CopyStreamPoll() to use WaitForMultipleObjects(). Microsoft's select() > > > doesn't support pipes and there's no socketpair(). > > > Any more straightforward ideas? > > > From a cursory look at history, it used to be that pg_basebackup had this > > > behaviour on all platforms, but it got fixed for other platforms in > > > 7834d20b57a by Tom (assuming the problem wasn't present there). > > > > Hmm --- I see that I thought Windows was unaffected, but I didn't > > consider this angle. > > > > Can we send the child process a signal to kick it off its wait? > > No. (1) on Windows it's not a child process, it's a thread. And (2) > Windows doesn't have signals. We emulate those *in the backend* for > win32, but this problem is in the frontend where that emulation layer > doesn't exist.
Actually, just after sending that... What we could do is do a WSACancelBlockingCall() which will cancel the select() thereby making us do the check. However, per the docs (https://docs.microsoft.com/en-us/windows/win32/api/winsock2/nf-winsock2-wsacancelblockingcall) this function is no longer exported in Winsock 2, so this does not seem to be the right way forward. There is no replacement function for it -- the suggestion is basically "don't do that, use multithreading instaed" which I think brings us back to the original suggestion of WSAEventSelect(). -- Magnus Hagander Me: https://www.hagander.net/ Work: https://www.redpill-linpro.com/
