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

Srikar Dronamraju
2011-03-15T18:13:50Z

* Thomas Gleixner <tglx@linutronix.de> [2011-03-15 19:03:44]:

> 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.

We no more call it write locked. So we can drop the reference to
write lock.