lkml.org 
[lkml]   [2019]   [Feb]   [21]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH 1/1] RDMA/odp: convert to use HMM for ODP
On Wed, Feb 20, 2019 at 05:29:24PM -0500, Jerome Glisse wrote:
> > >
> > > Yes it is safe, the hmm struct has its own refcount and mirror holds a
> > > reference on it, the mm struct itself has a reference on the mm
> > > struct.
> >
> > The issue here is that that hmm_mirror_unregister() must be a strong
> > fence that guarentees no callback is running or will run after
> > return. mmu_notifier_unregister did not provide that.
> >
> > I think I saw locking in hmm that was doing this..
>
> So pattern is:
> hmm_mirror_register(mirror);
>
> // Safe for driver to call within HMM with mirror no matter what
>
> hmm_mirror_unregister(mirror)
>
> // Driver must no stop calling within HMM, it would be a use after
> // free scenario

This statement is the opposite direction

I want to know that HMM doesn't allow any driver callbacks to be
running after unregister - because I am going to kfree mirror and
other memory touched by the driver callbacks.

Jason

\
 
 \ /
  Last update: 2019-02-22 00:00    [W:0.052 / U:0.128 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site