On Wed, Jul 16, 2014 at 08:57:38PM +0530, Chetan Nanda wrote:
On Wed, Jul 16, 2014 at 8:49 PM, Chetan Nanda <chetannanda@gmail.com> wrote:
On Wed, Jul 16, 2014 at 6:39 PM, John de la Garza <john@jjdev.com> wrote:
On Wed, Jul 16, 2014 at 04:00:18PM +0530, Chetan Nanda wrote: > A depends on B, so B is automatically loaded when A is loaded. > B module is also directly being used by the user side code via misc > interface. >. > Now when I am unloading module A, via "modprobe -r A" it is also unloading > the module B which is being used by the application and resulting in the > kernel crash.
You said that A depends on B, right? Why do you have A dependng on B? If it A needs to have B then it makes sense that you can not remove A while B is in use. If A doesn't need B, why not remove the dependency.
A is calling few APIs defined by B.
But why when user space application is already using module B. (it has already open its device fd) kernel allows to remove it.
I tried with doing try_module_get() in the module's open function, it prevent module B unloading but cause thread doing modprobe -r to hang Is there any other way to mark module as busy when being used by user application?
Never use try_module_get(), that is racy. What is the user/kernel interface you are using, and why doesn't it automatically increase the module count when userspace opens the interface? It should all be done in a way that your module doesn't need to do anything special. thanks, greg k-h