On Tue, Oct 13, 2015 at 5:35 AM, Tom Lane <t...@sss.pgh.pa.us> wrote:
> I wrote:
>> This is kind of a mess :-(.  But it does look like what we want is
>> for SubPostmasterMain to do more than nothing when it chooses not to
>> reattach.  Probably that should include resetting UsedShmemSegAddr to
>> NULL, as well as closing the handle.
> After poking around a bit more, I propose the attached patch.  I've
> checked that this is happy with an EXEC_BACKEND Unix build, but I'm not
> able to test it on Windows ... would somebody do that?
> BTW, it appears from this that Cygwin builds have been broken right along
> in a different way: according to the code in sysv_shmem's
> PGSharedMemoryReAttach, Cygwin does cause a re-attach to occur, which we
> were not undoing for putatively-not-connected-to-shmem child processes.
> That's a robustness problem because it breaks the postmaster's expectation
> that it's safe to not reinitialize shmem after a crash of one of those
> processes.  I believe this patch fixes that problem as well, though if
> anyone can test it on Cygwin that wouldn't be a bad thing either.

I don't have a Cygwin environment at hand. That's unfortunate..

Looking at the patch, clearly +1 for the additional routine in both
win32_shmem.c and sysv_shmem.c to clean up the shmem state at backend
level. I have played as well with the patch on Windows and it behaves
as expected: without the patch a process killed with taskkill /f stops
straight the server even if restart_on_crash is on. With the patch the
server restarts correctly.

(Sorry, I should have mentioned that my last patch was untested and
*surely broken*, that was the result of a 3-min guess to make the
cleanup more generic for child processes that do not need to be
attached to shmem).

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