Re: [patch] lockless, scalable get_pid(), for_each_process() elimination, 2.5.35-BK

From: William Lee Irwin III (
Date: Wed Sep 18 2002 - 12:50:55 EST

On Wed, 18 Sep 2002, William Lee Irwin III wrote:
>> There were only 10K tasks, with likely consecutively-allocated PID's,
>> and some minor background fork()/exit() activity, but there are more
>> offenders on the read side than get_pid() itself.
>> There is no question of PID space: the full 2^30 was configured in the
>> tests done after the PID space expansion.

On Wed, Sep 18, 2002 at 07:59:50PM +0200, Ingo Molnar wrote:
> oh. Well, there are a whole lot of other places in the unpatched kernel
> that iterate over every task. So with the patch applied, all these lockups
> go away?
> Ingo

Not quite all of them. top(1) takes out the machine by triggering calls
to get_pid_list(), which NMI oopses fork() and exit() on other cpus.

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