lkml.org 
[lkml]   [2001]   [Oct]   [19]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: 2.4.13pre5aa1
From
Date
On Fri, 2001-10-19 at 00:19, Andrea Arcangeli wrote:
> Only in 2.4.13pre3aa1: 00_files_struct_rcu-2.4.10-04-1
> Only in 2.4.13pre5aa1: 00_files_struct_rcu-2.4.10-04-2

I want to point out to preempt-kernel users that RCU is not
preempt-safe. The implicit locking assumed from per-CPU data structures
is defeated by preemptibility.

(Actually, FWIW, I think I can think of ways to make RCU preemptible but
it would involve changing the write-side quiescent code for the case
where the pointers were carried over the task switches. Probably not
worth it.)

This is not to say RCU is worthless with a preemptible kernel, but that
we need to make it safe (and then make sure it is still a performance
advantage, but I don't think this would add much overhead). Note this
is clean, simply wrapping the read code in non-preemption statements.

I will hack up a patch when I get the time, but I would like to prevent
myself from maintaining the patch against a third tree ... where, oh
where, is 2.5? :)

Robert Love

-
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 13:08    [W:0.082 / U:1.380 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site