Re: [PATCH 6/7] vt: Update spawnpid to be a struct pid_t

From: Eric W. Biederman
Date: Tue Aug 15 2006 - 14:43:00 EST

Alan Cox <alan@xxxxxxxxxxxxxxxxxxx> writes:

> Ar Maw, 2006-08-15 am 12:23 -0600, ysgrifennodd Eric W. Biederman:
>> This keeps the wrong process from being notified if the
>> daemon to spawn a new console dies.
> Not sure why we count pids not task structs but within the proposed
> implementation this appears correct so

Basically struct pid is relatively cheap, 64bytes or so.
struct task is expensive 10K or so, when all of the stacks
and everything are included.

Counting pids allows the task to exit in user space and free up
all of it's memory.

When /proc used to count the task struct it was fairly easy to
deliberately oom a 32bit machine just by open up directories in
/proc and then having the process exit. rlimits didn't help because
we don't count processes that have exited.

> Acked-by: Alan Cox <alan@xxxxxxxxxx>

Thanks. When I get to the tty portion of this I think I am going
to have to synchronize with you as last I looked you were working in
this area as well.


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