On Tue, Sep 4, 2012 at 4:09 PM, Julian Andres Klode <jak@jak-linux.org> wrote:

On Tue, Sep 04, 2012 at 03:58:20PM +0530, Manavendra Nath Manav wrote:

...

On Tue, Sep 4, 2012 at 3:00 PM, Manavendra Nath Manav <mnm.kernel@gmail.com> wrote:

...

Hi,

I have declared a static const int variable in one driver and exported that variable symbol. In another driver i am modifying that variable.

No, you did not export it. It's static (and static is kind of the opposite of extern). And then you try to assign a value to a non-static variable with the same name, which might not even exist (as the other is static, this should not even work in my opinion).

...

...

The other driver prints the modified value but the original driver retains the original value. When both virtual and physical addresses of the variable as seen by both drivers are same, how is this even possible. Is it a kernel bug?

It only works because the compiler optimized the value = 123 away, and replaced value with 123 in the first module everywhere, as it is declared const and thus cannot be changed, so there's no reason to read it from memory.

-- Julian Andres Klode - Debian Developer, Ubuntu Member

See http://wiki.debian.org/JulianAndresKlode and http://jak-linux.org/.

Still I am not able to understand !! Why the output behaviour changes when the declaration is made as "const volatile". I get the same results as above when i remove "static" and retain "const". -- Manavendra Nath Manav