Messages in this thread |  | | | Date | Fri, 27 Feb 2009 08:54:41 +0100 | | Subject | correct locking in softirq | | From | Giacomo <> |
| |
Good morning
Harald Welte's "The journey of a packet through the Linux 2.6.10 network stack" article says that packet travelling inside linux kernel 2.6 (the receive / input part) runs in softirq context.
Hooking with netfilter's hooks in a kernel module, i need to read for each packet received a list of rules.
Since in input and prerouting hooks the context is softirq (perhaps also in forward?), I need some read lock feature.
I currently use RCU lists and, while reading lists I use
READ
read_lock_bh()
together with list_for_each_rcu()
When changing, or flushing, rules, I use
WRITE
spin_lock() + list_add_tail_rcu() (adding)
or spin_lock() + list_for_each_entry() (for listing and then freeing with list_del_rcu() and call_rcu() )
The question is:
- is the read part above correct? - do I really need _bh()? or should I use simply read_lock() ?
Thanks in advance
Giacomo
-- Giacomo S. http://www.giacomos.it
- - - - - - - - - - - - - - - - - - - - - -
* Aprile 2008: iqfire-wall, un progetto open source che implementa un filtro di pacchetti di rete per Linux, e` disponibile per il download qui: http://sourceforge.net/projects/ipfire-wall
* Informazioni e pagina web ufficiale: http://www.giacomos.it/iqfire/index.html
- - - - - - - - - - - - - - - - - - - - - -
. '' `. : :' : `. ` ' `- Debian GNU/Linux -- The power of freedom http://www.debian.org
|  |