Re: [PATCH v2 2.6.38-rc8-tip 3/20] 3: uprobes: Breakground page replacement.

Thomas Gleixner
2011-03-15T18:04:42Z

On Tue, 15 Mar 2011, Srikar Dronamraju wrote:

> * Thomas Gleixner <tglx@linutronix.de> [2011-03-15 14:22:09]:
>
> > On Mon, 14 Mar 2011, Srikar Dronamraju wrote:
> > > +/*
> > > + * Called with tsk->mm->mmap_sem held (either for read or write and
> > > + * with a reference to tsk->mm
> >
> > Hmm, why is holding it for read sufficient?
>
> We are not adding a new vma to the mm; but just replacing a page with
> another after holding the locks for the pages. Existing routines
> doing close to similar things like the
> access_process_vm/get_user_pages seem to be taking the read_lock. Do
> you see a resaon why readlock wouldnt suffice?

No, I just was confused by the comment. Probably should have asked why
you want to call it write locked.

Thanks,

tglx