Messages in this thread | | | Subject | Re: [PATCH] simplify/fix first_tid() | From | (Eric W. Biederman) | Date | Mon, 20 Mar 2006 11:56:56 -0700 |
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Oleg Nesterov <oleg@tv-sign.ru> writes:
> "Eric W. Biederman" wrote: >> This is better however if I read this code correctly. It modifies >> the code so the last time user space goes trough this loop >> with nr > nr_threads. Then we will walk the entire threads >> list to achieve nothing. > > This can happen only if the thread we stopped at has exited, and > some other threads have exited too, so that nr >= ->signal->count. > > I think it's not worth optimizing this rare and anyway slow path. > However, you are the code author, I'll send a trivial patch which > restores this optimization if you don't change you mind. > >> So we really still need the nr_threads test in there so we don't >> traverse the list twice everytime through readdir. > > How so? We don't do it twice?
In general user space does. Because a read of 0 bytes signifies the end of a directory.
So we have 2 trips through proc_task_readdir initiated by user space.
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