help linked lists and locks

[Giacomo Strangolino]

Good morning.
In a packet filter which i wrote on my own, i have a linked list of 
structures
which i read periodically by means of list_for_each_safe macro.
These structures have a timer, when it expires, the entry is deleted.
The timer can on the other way be updated by mod_timer.

The context of execution is that of a software interrupt (i attach my 
code at
netfilter hooks), and some times (after tenths of millions of packets 
filtered)
the system goes into panic.

I think i should put some locks when reading in list_for_each or when
deleting an item, or when updating timers.

I thought it was not necessary because of the atomic context.

In fact, should i use read/write_lock? Or spinlocks?

Should i put the locks when reading in list_for_each, when adding an entry
with list_add, when deleting with list_del and also when mod_timer?

I verified that when i put those locks, things go better, but do i need them
so many in my code?

Thanks in advance

Giacomo.