| > +/**
| > + * ccid_request_module - Pre-load CCID module for later use
| > + * This should be called only from process context (e.g. during connection
| > + * setup) and is necessary for later calls to ccid_new (typically in software
| > + * interrupt), so that it has the modules available when they are needed.
| > + */
| > +static int ccid_request_module(u8 id)
| > +{
| > + if (!in_atomic()) {
|
| Shouldn't the above be in a BUG_ON? It looks strange to simply refuse to
| do that and return OK.
|
| > + ccids_read_lock();
| > + if (ccids[id] == NULL) {
| > + ccids_read_unlock();
| > + return request_module("net-dccp-ccid-%d", id);
| > + }
| > + ccids_read_unlock();
| > + }
| > + return 0;
| > +}
We can do this if you want, but in a way this is a suggestion for the
existing code, compare with the original from ccid_new() below
ccids_read_lock();
#ifdef CONFIG_MODULES
if (ccids[id] == NULL) {
/* We only try to load if in process context */
ccids_read_unlock();
if (gfp & GFP_ATOMIC)
goto out;
request_module("net-dccp-ccid-%d", id);
ccids_read_lock();
}
#endif
==> gfp is atomic when called from dccp_feat_update_ccid(), which is why
in the previous feature-negotiation code DCCP crashed when trying to
negotiate any CCID module that had not been loaded:
new_ccid = ccid_new(new_ccid_nr, sk, rx, GFP_ATOMIC);
meant that the module would not be reloaded.
==> On the other hand, when called via ccid_hc_{rx,tx}_new(), gfp=GFP_KERNEL
and so an attempted module load would succeed. This explains why loading
worked when starting with the default (non-negotiated) CCIDs.
==> So how do we remain? I am ok turning the above into a BUG_ON.
As an alternative, since the function is only called in a single
place (the initialisation of feat.c), we could consider removing the
function entirely and merge its contents into dccp_feat_init().
Would that be better?
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