Re: Function written in C, hangs on one machine and not another...

Thanks to the great suggestions I've at least gotten it to not hang...

Martijn's hint about blocking led me to open up those filehandles in a
non-blocking mode. It appears that write() will write, at a maximum, only 4096
bytes when it is called from within PostgreSQL. I've tried to push data into it
in <=4096-byte slugs, but after 4096 bytes it just won't take anymore. Since (I
think) using a non-blocking mode could cause problems with thread safety, it's
probably a lost cause.

I'm new to C, so this may seem extremely naive: I'm not sure how to use exec()
to solve this problem. Could you give me a few pointers to get me started?

--- Douglas McNaught <doug(at)mcnaught(dot)org> wrote:

> Martijn van Oosterhout <kleptog(at)svana(dot)org> writes:
>
> > The things that have screwed me up in the past with pulling tricks like
> > this are:
> >
> > 1. Program has registered atexit() handlers. _exit() avoids this.
> > 2. Pending stdio output that gets flushed. The backend doesn't use
> > stdio much so you might be fine here.
> > 3. Signals. Make sure you don't get sent signals that screw state.
> > Might be wise to block them all, or reset them all to default.
> >
> > Truly, exec() is the cleanest way to solve all this, it simply replaces
> > the current process, lock, stock and barrel.
>
> Definitely. It would probably also be good to close all file
> descriptors (except for stdin/etdout/stderr) before exec(), just in
> case the other binary does something screwy with random file
> descriptors (which it obviously shouldn't).
>
> -Doug
>
> ---------------------------(end of broadcast)---------------------------
> TIP 2: Don't 'kill -9' the postmaster
>

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