Patrick McHardy <[EMAIL PROTECTED]> writes: > No, you need to add your own locking to prevent this, something > list this: > > registration/unregistration: > > take lock > change proto_tab[] > release lock > > lookup: > > take lock > cp = proto_tab[] > if (cp && !try_module_get(cp->owner)) > cp = NULL > release lock
Ah, ok. Thanks for that hint. I will add it that way. > > 2. If the module gets unloaded after the first check and > > request_module() but before the call to try_module_get() the > > socket() syscall will return with error, although module auto > > loading would normally be successful. How can I prevent that? > > > Why do you want to prevent it? The admin unloaded the module, > so he apparently doesn't want the operation to succeed. Well, unloading a module doesn't usually cause to operation to fail when auto loading is enabled. It only wouldn't succeed when the unload happens in the small window between test/request-module and call to try_module_get(). This looks ugly to me. But the lock you described above would also solve this. > I'm saying you need _rcu for the *read side*. All operations changing > the list already use the _rcu variants. > > > I'm sorry if I miss something > > obvious here, but could you try to explain it to me? > > > spin_lock_bh only disables BHs locally, other CPUs can still process > softirqs. And since rcv_lists_lock is only used in process context, > the BH disabling is actually not even necessary. Well, I finally (hopefully) got it and I have changed the code accordingly. Thanks for your explanation. I will post our updated code again, probably today. The issues still left are * module parameter for loopback, but we want to keep that. * configure option for allowing normal users access to raw and bcm CAN sockets. I'll check how easily an (embedded) system can be set up to run relevant/all processes with the CAP_NEW_RAW capability. I would like to kill that configure option. * seq_files for proc fs. On my TODO list. urs - To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html
