Luben Tuikov <luben_tuikov@xxxxxxxxxxx> wrote: > On 08/07/05 17:57, James Bottomley wrote: > > Alan Stern wrote: > >>The only resource that matters for this discussion is associated with the > >>LLD itself, not with any of its hosts: the host template. Once the SCSI > >>core has released all references to the template, it can't call the LLD > >>any more. The problem is that the LLD has no way to know when all the > >>references have been dropped. This suggests that the entire problem could > >>be solved by adding a kref to struct scsi_host_template. > >> > >>Would you agree to a patch adding such a kref? > > > > > > Well, not really. The host template usually exists as a variable in the > > module, so its lifetime is tied to the lifetime of the module. Adding a > > kref wouldn't help because it will still be freed when the module is > > removed. If there's a case where the template is being freed > > prematurely because the module is being removed, then we have the module > > refcounting wrong somewhere. Have you run across such a case? > > Hmm, I think Alan has a point. > > >From object point of view, who is the parent and who is the child > when talking about LLDD/module and the host template? > > The reason is that the host template could be simulated on behalf > of the underlying transport (as is the case for USB). > > So, it could be the case that the host template _should_ be > removed but the entity which removed it should stay, and that > entity wants to know when the host template is to be removed. > > (Actually it doesn't, but setting the release method in the > kobj_ktype would do wonders. ;-) ) > > In which case, it does make sense to include a kset to the > host template (since it has many children), and anyone > using/manipulating it does kset_get(). When that entity > is done with the host template it does a kset_put(). > > Such entities could be the managing layer above, error > handling, etc. > > Another solution, just as good, is to use the template > _only_ for the registration call, as a _template_, and > as soon as the registration call has returned, the > caller (LLDD/module) can free the template. After all, > it is only a template. While you could do this I believe this would not solve Alan's question as if I read correctly it involved the functions called through the host template (i.e., through shost->hostt). > > Then the managing layer allocates the actual host struct > and "gives" it to the LLDD. The LLDD goes a kset_get() > on it while it lives, and when it is to die, it does a > kset_put(). And if it gets a method call, it would > error it out, after the put... > We already have kobject for the scsi_host object so it is unclear why switch to a kset. In looking at the kernel tree I do not see any users of ksets outside the driver model subsystems. I believe James suggestion of adding to scsi_host_dev_release would allow the LLDD to get a better indicator of release cleanup without changing the LLDD interface to use ksets. -andmike -- Michael Anderson andmike@xxxxxxxxxx - : send the line "unsubscribe linux-scsi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
