From: | Hal Snyder <hal(at)enteract(dot)com> |
---|---|
To: | hackers(at)postgreSQL(dot)org |
Subject: | Re: [HACKERS] Query cancel and OOB data (fwd) |
Date: | 1998-06-01 05:33:35 |
Message-ID: | 199806010533.BAA03855@hub.org |
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Lists: | pgsql-hackers |
> From: Bruce Momjian <maillist(at)candle(dot)pha(dot)pa(dot)us>
> Date: Mon, 1 Jun 1998 00:53:21 -0400 (EDT)
...
> > Just do time and pid. But get the time from gettimeofday so it will be
> > down to the millisecond or so. Anything more is overkill for this application.
>
> You have given me exactly what I needed. If I run gettimeofday() on
> postmaster startup, and run it when the first backend is started, I can
> use the microseconds from both calls to generate a truely random seed.
> Even if the clock is only accurate to 10 ms, I still get a 10,000 random
> keyspace. I can mix the values by taking/swapping the low and high
> 16-bit parts so even with poor resolution, both get used.
>
> The micro-second times are not visible via ps, or probably even kept in
> the kernel, so these values will work fine.
>
> Once random is seeded, for each backend we call random twice and return
> a merge of the two random values. I wonder if we just call random once,
> and XOR it with our randeom seed, if that would be just as good or
> better? Cryptologists?
>
> Comments? Sounds like a plan. The thought of giving the users yet
> another option to disable cancel just made me squirm.
For FreeBSD and Linux, isn't /dev/urandom the method of choice for
getting random bits? [I've been away from this thread awhile - please
excuse if this option was already discussed].
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