On Thu, Feb 20, 2025 at 12:40:20AM +0800, Alan Huang wrote:
> On Feb 18, 2025, at 08:50, Wei Yang <richard.weiyang@xxxxxxxxx> wrote:
> >
> > This patch adjust the example code with following two purpose:
> >
> > * reduce the confusion on not releasing e->lock
> > * emphasize e is valid and not stale with e->lock held
> >
> > Signed-off-by: Wei Yang <richard.weiyang@xxxxxxxxx>
> > CC: Boqun Feng <boqun.feng@xxxxxxxxx>
> > CC: Alan Huang <mmpgouride@xxxxxxxxx>
> >
> > ---
> > v2:
> > * add the missing parameter *key
> > * make function return struct audit_entry
> > ---
> > Documentation/RCU/listRCU.rst | 10 ++++++----
> > 1 file changed, 6 insertions(+), 4 deletions(-)
> >
> > diff --git a/Documentation/RCU/listRCU.rst b/Documentation/RCU/listRCU.rst
> > index ed5c9d8c9afe..d8bb98623c12 100644
> > --- a/Documentation/RCU/listRCU.rst
> > +++ b/Documentation/RCU/listRCU.rst
> > @@ -334,7 +334,7 @@ If the system-call audit module were to ever need to reject stale data, one way
> > to accomplish this would be to add a ``deleted`` flag and a ``lock`` spinlock to the
> > ``audit_entry`` structure, and modify audit_filter_task() as follows::
> >
> > - static enum audit_state audit_filter_task(struct task_struct *tsk)
> > + static struct audit_entry *audit_filter_task(struct task_struct *tsk, char **key)
> > {
> > struct audit_entry *e;
> > enum audit_state state;
> > @@ -346,16 +346,18 @@ to accomplish this would be to add a ``deleted`` flag and a ``lock`` spinlock to
> > if (e->deleted) {
> > spin_unlock(&e->lock);
> > rcu_read_unlock();
> > - return AUDIT_BUILD_CONTEXT;
> > + return NULL;
> > }
> > rcu_read_unlock();
> > if (state == AUDIT_STATE_RECORD)
> > *key = kstrdup(e->rule.filterkey, GFP_ATOMIC);
> > - return state;
> > + /* As long as e->lock is held, e is valid and
> > + * its value is not stale */
> > + return e;
> > }
> > }
> > rcu_read_unlock();
> > - return AUDIT_BUILD_CONTEXT;
> > + return NULL;
> > }
> >
> > The ``audit_del_rule()`` function would need to set the ``deleted`` flag under the
> > --
> > 2.34.1
> >
>
> I think it’s good enough to illustrate the intention here:
>
> Reviewed-by: Alan Huang <mmpgouride@xxxxxxxxx>
>
Queued for further tests and reviews, thanks you both!
> Boqun, there is an unreviewed doc patch[1] that fixes the section
>
> “Using RCU hlist_nulls to protect list and objects”
>
> [1] https://lore.kernel.org/rcu/20240326124431.77430-1-mmpgouride@xxxxxxxxx/
>
> : )
>
Will take a look later.
Regards,
Boqun
>
>
>
