Thread: Win32 processCancelRequest/waitpid (was fork/exec patch : pre-CreateProcess finalization)

I wrote:
> But I'll happily concede the point, and prove it by knocking
> up a patch for it over the weekend (unless anyone else
> particularly wants to).

Occurs to me I could kill 2 birds with one stone, and also implement another
Win32 sticking point, namely the waitpid changes for the Postmaster, by
having win32_forkexec do one of the following:

a) - when a backend startup is indicated, add a pid/cancel_key struct
(Backend) to this new array in shared mem
   - when any child of the postmaster is started, also add a pid/HANDLE
struct to a postmaster local array (or perhaps a dlllist)

b) - when any child of the postmaster is started, add a
pid/cancel_key/HANDLE/isBackend struct to this new array in shared mem

(HANDLE for waiting on to determine child death; isBackend to separate
BackendList backends from other children)

Choosing a over b:
    PRO: as we've already been through, keeps the postmaster-only data
local to the postmaster, stopping tampering from rouge backends
    CON: yet more redundancy

Given recent conversations, I'm guessing (a), but any comments before going
ahead and doing it?

Claudio

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Claudio Natoli wrote:
>
> I wrote:
> > But I'll happily concede the point, and prove it by knocking
> > up a patch for it over the weekend (unless anyone else
> > particularly wants to).
>
> Occurs to me I could kill 2 birds with one stone, and also implement another
> Win32 sticking point, namely the waitpid changes for the Postmaster, by
> having win32_forkexec do one of the following:
>
> a) - when a backend startup is indicated, add a pid/cancel_key struct
> (Backend) to this new array in shared mem
>    - when any child of the postmaster is started, also add a pid/HANDLE
> struct to a postmaster local array (or perhaps a dlllist)
>
> b) - when any child of the postmaster is started, add a
> pid/cancel_key/HANDLE/isBackend struct to this new array in shared mem
>
> (HANDLE for waiting on to determine child death; isBackend to separate
> BackendList backends from other children)
>
> Choosing a over b:
>     PRO: as we've already been through, keeps the postmaster-only data
> local to the postmaster, stopping tampering from rouge backends
>     CON: yet more redundancy
>
> Given recent conversations, I'm guessing (a), but any comments before going
> ahead and doing it?

As I understand it, the postmaster shared memory idea is good because
only the postmaster writes to it, and only the backends read from it.
If the HANDLE works the same way, I think you should put it into the
shared memory too, hence (b).

[ FYI, I haven't seen you on IM lately.]

--
  Bruce Momjian                        |  http://candle.pha.pa.us
  pgman@candle.pha.pa.us               |  (610) 359-1001
  +  If your life is a hard drive,     |  13 Roberts Road
  +  Christ can be your backup.        |  Newtown Square, Pennsylvania 19073

Bruce Momjian <pgman@candle.pha.pa.us> writes:
> As I understand it, the postmaster shared memory idea is good because
> only the postmaster writes to it, and only the backends read from it.
> If the HANDLE works the same way, I think you should put it into the
> shared memory too, hence (b).

But the postmaster needs to use the HANDLE, hence not (b).

            regards, tom lane

Tom Lane wrote:
> Bruce Momjian <pgman@candle.pha.pa.us> writes:
> > As I understand it, the postmaster shared memory idea is good because
> > only the postmaster writes to it, and only the backends read from it.
> > If the HANDLE works the same way, I think you should put it into the
> > shared memory too, hence (b).
>
> But the postmaster needs to use the HANDLE, hence not (b).

That's where I was unclear.  If the postmaster has to read the HANDLE,
we are better with keeping it in local memory (a).

--
  Bruce Momjian                        |  http://candle.pha.pa.us
  pgman@candle.pha.pa.us               |  (610) 359-1001
  +  If your life is a hard drive,     |  13 Roberts Road
  +  Christ can be your backup.        |  Newtown Square, Pennsylvania 19073