Re: [PATCH] dlm: wait for outstanding SRCU callbacks to complete in exit paths

[Alexander Aring]

Hi,

On Wed, Sep 2, 2026 at 10:30 AM Zqiang <qiang.zhang@xxxxxxxxx> wrote:
>
> >
> > >
> > > Hi,
> > >
> > >  On Tue, Sep 1, 2026 at 5:19 AM Zqiang <qiang.zhang@xxxxxxxxx> wrote:
> > >
> > >
> > >  The dlm_lowcomms_exit() and dlm_midcomms_exit() iterate over the
> > >  srcu protected connection and node hash tables and hand each
> > >  element to call_srcu() for deferred freeing (connection_release()
> > >  and midcomms_node_release()). call_srcu() is asynchronous: the
> > >  callbacks are invoked only after an SRCU grace period, which may
> > >  happen after the exit function has already returned.
> > >
> > >  These exit functions are reached from exit_dlm() on module unload.
> > >  Once they return, module teardown continues and the module text
> > >  may be unloaded while call_srcu() callbacks are still pending. When
> > >  such a callback finally runs, it executes freed module code and
> > >  touches the static SRCU domains that are being torn down, resulting
> > >  in a use-after-free.
>
>      I should rephrase it:
>
>      Due to missed call to the srcu_barrier(), when invoke cleanup_srcu_struct()

Then there need to be a MUST call of srcu_barrier() before
cleanup_srcu_struct() every time.

I am confused here.

- Alex