Linux Kernel module programming help

[JackLee]

Hi,all , I am making a kernel module now , it works fine in 2.4 kernel , now I am porting it to readhat es 5 (2.6.18. ,something puzzled me for about 2 weeks.

in my module

......
#include <net/pkt_sched.h> /*for use the qdisc_run and*/

int ip_packet_send_skb(struct rtp_sock *sk , struct sk_buff *skb1)
{
.....................

if (q->enqueue) {
q->enqueue(skb, q);
qdisc_run(sk->dev);
}
.....................

}

when i ma comping the module ,there is always a warning of __qdisc_run undefined symbol .
i look this symbol up in the /proc/kallsyms , there is a __qdisc_run ,
and the kernel I am runing is build by the source code under /usr/src/kernel/2.6.18..... ,when I use modinfo iphook.ko , the version info is the same as the result of uname -r .

qdisc_run is defined in the "pkt_sched.h"
like the folowing (kernel souce code ):
#include <net/sch_general.h>
extern void __qdisc_run(struct net_device *dev);

static inline void qdisc_run(struct net_device *dev)
{
if (!netif_queue_stopped(dev) &&
!test_and_set_bit(__LINK_STATE_QDISC_RUNNING, &dev->state))
__qdisc_run(dev);
}

in net/sch_general.h:
extern void qdisc_lock_tree(struct net_device *dev);
extern void qdisc_unlock_tree(struct net_device *dev);
/*here there is no declare of __disc_run , but I think it no the problem ,since in pkt_sched.h , there is a extern void __qdisc_run(struct net_device *dev);
*/


in sch_general.c
#include <net/sch_general.h>
void qdisc_lock_tree(struct net_device *dev)
{
write_lock(&qdisc_tree_lock);
spin_lock_bh(&dev->queue_lock);
}

void qdisc_unlock_tree(struct net_device *dev)
{
spin_unlock_bh(&dev->queue_lock);
write_unlock(&qdisc_tree_lock);
}

void __qdisc_run(struct net_device *dev)
{
if (unlikely(dev->qdisc == &noop_qdisc))
goto out;

while (qdisc_restart(dev) < 0 && !netif_queue_stopped(dev))
/* NOTHING */;

out:
clear_bit(__LINK_STATE_QDISC_RUNNING, &dev->state);
}



what puzzled me is :
these 3 function (_disc_run , disc_lock_tree, disc_unlock_tree)
1. implemented in the same c file
2. all in the /proc/kallsyms
3 all included in the pkt_sched.h
(disc_lock_tree, disc_unlock_tree included by include sch_general.h , __disc_run inclued by explicit "extern")

but why when I am compling my module , only the __qdisc_run undefined (when I use disc_lock_tree , disc_unlock_tree , it is ok )

[JackLee]

anybody help?
eager to know why

[JackLee]

I got the answer by reading the kernel code .
the result is :
no all the symbols in the kallsyms can be called by kernel modules , only those symbols exported by (export_symbols)can be called .

another question , is there any other way to know the subset of the symbols can be called in the kallsyms?