On Sat, Jan 8, 2011 at 19:01, Mikulas Patocka <mpatocka@xxxxxxxxxx> wrote: > On Sat, 8 Jan 2011, Kay Sievers wrote: >> On Sat, Jan 8, 2011 at 14:19, Mikulas Patocka <mpatocka@xxxxxxxxxx> 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. ÂIt'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 -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
