Messages in this thread | | | From | Kay Sievers <> | Date | Sat, 8 Jan 2011 19:09:03 +0100 | Subject | Re: kobject_put vs module unload |
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On Sat, Jan 8, 2011 at 19:01, Mikulas Patocka <mpatocka@redhat.com> wrote: > On Sat, 8 Jan 2011, Kay Sievers wrote: >> On Sat, Jan 8, 2011 at 14:19, Mikulas Patocka <mpatocka@redhat.com> wrote: >> > On Fri, 7 Jan 2011, Greg KH wrote: >> >> >> > 4) the reference obtained at point 1) is dropped, kobject reference count >> >> > reaches zero and the release callback is called. But that callback points >> >> > to an unloaded module and causes a crash. >> >> > >> >> > How is it solved? Am I missing something? >> >> >> >> You have the code that creates and frees the object, to not be in the >> >> module that could have been unloaded. It's really just that simple. >> > >> > If the whole device mapper subsystem can be a module, where can I put the >> > code? >> > >> > I think a similar bug exists in md, it can also be unloaded as a module >> > and it has "release" method in its module code. >> >> If you still have data structures hanging around, these structures are >> supposed to take a reference on the module -- and you can not unload >> the module as long as this is the case. >> >> Kay > > kobject references don't increase module reference count. If kobject held > module references, it would be a fix for this bug, but could cause other > bugs (some modules could be unloadable due to self-references to its own > kobjects).
Sure, they don't automatically take references. It's the job of the driver/module, to make sure to pin the module for any data of it, which might be still in use.
Kay -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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