lkml.org 
[lkml]   [2001]   [Sep]   [25]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: Locking comment on shrink_caches()


On Tue, 25 Sep 2001, David S. Miller wrote:

> From: Marcelo Tosatti <marcelo@conectiva.com.br>
> Date: Tue, 25 Sep 2001 14:49:40 -0300 (BRT)
>
> Do you really need to do this ?
>
> if (unlikely(!spin_trylock(&pagecache_lock))) {
> /* we hold the page lock so the page cannot go away from under us */
> spin_unlock(&pagemap_lru_lock);
>
> spin_lock(&pagecache_lock);
> spin_lock(&pagemap_lru_lock);
> }
>
> Have you actually seen bad hold times of pagecache_lock by
> shrink_caches() ?
>
> Marcelo, this is needed because of the spin lock ordering rules.
> The pagecache_lock must be obtained before the pagemap_lru_lock
> or else deadlock is possible. The spin_trylock is an optimization.

Not, it is not.

We can simply lock the pagecachelock and the pagemap_lru_lock at the
beginning of the cleaning function. page_launder() use to do that.

Thats why I asked Andrea if there was long hold times by shrink_caches().

-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/

\
 
 \ /
  Last update: 2005-03-22 13:03    [W:0.097 / U:7.384 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site