Re: [PATCH v2 2.6.38-rc8-tip 7/20] 7: uprobes: store/restore original instruction.

Srikar Dronamraju
2011-03-15T16:31:10Z

* Thomas Gleixner <tglx@linutronix.de> [2011-03-15 15:41:20]:

> On Mon, 14 Mar 2011, Srikar Dronamraju wrote:
> > static int install_uprobe(struct mm_struct *mm, struct uprobe *uprobe)
> > {
> > - int ret = 0;
> > + struct task_struct *tsk;
> > + int ret = -EINVAL;
> >
> > - /*TODO: install breakpoint */
> > - if (!ret)
> > + get_task_struct(mm->owner);
>
> Increment task ref before checking for NULL ?

In response to earlier comments/suggestions from Stephen Wilson, we
resolved to handle it this way

static uprobes_get_mm_owner() {
struct task_struct *tsk;

rcu_read_lock()
tsk = rcu_dereference(mm->owner);
if (tsk)
get_task_struct(tsk);
rcu_read_unlock();
return tsk;
}

Both install_uprobe and remove_uprobe will end up calling uprobes_get_mm_owner().

--
Thanks and Regards
Srikar