Capturing all writes as fault on a memory mapped page.

[Pranay Srivastava]

On 5/28/14, Greg KH <greg at kroah.com> wrote:
> On Wed, May 28, 2014 at 07:13:55PM +0530, Pranay Srivastava wrote:
>> Actually trying to do something like if there's a write being done on
>> the page by a task currently then other tasks should wait( was hoping
>> that the fault handler code would be called for write but doesn't
>> happen that way).
>
> If you have multiple writers on the same page, why would you want any
> other writer to wait?  That's the joy of mmap, you don't have to worry
> about any of this from userspace, the kernel backing store handles it
> all for you automatically.
>
>> Yes through write operation I can do with mutex but I was wondering
>> what if this has to be done through mmap of my misc_device then no
>> read/write calls involved so just wanted to see how would I stop
>> multiple writes to my misc_device.
>
> Either you don't allow multiple opens, or you just live with the mess
> that userspace is wanting to do here.
>
>> Perhaps there are other methods as to how device memory can be mapped
>> to user space? or they aren't at all? Not really sure just reading and
>> trying.
>
> As you mapped it to userspace, it's now up to the user to deal with any
> serialization that it wants to enforce, it's out of the hands of your
> misc driver.
>

Thanks a lot.

> good luck,
>
> greg k-h
>


-- 
        ---P.K.S