Re: linux-5.13.2: warning from kernel/rcu/tree_plugin.h:359

[Zhouyi Zhou <zhouzhouyi@gmail.com>]

On Mon, Jul 19, 2021 at 10:44 AM Matthew Wilcox <willy@infradead.org> wrote:
>
> On Mon, Jul 19, 2021 at 10:24:18AM +0800, Zhouyi Zhou wrote:
> > Meanwhile, I examined the 5.12.17 by naked eye, and found a suspicious place
> > that could possibly trigger that problem:
> >
> > struct swap_info_struct *get_swap_device(swp_entry_t entry)
> > {
> >      struct swap_info_struct *si;
> >      unsigned long offset;
> >
> >      if (!entry.val)
> >              goto out;
> >     si = swp_swap_info(entry);
> >     if (!si)
> >        goto bad_nofile;
> >
> >    rcu_read_lock();
> >   if (data_race(!(si->flags & SWP_VALID)))
> >      goto unlock_out;
> >   offset = swp_offset(entry);
> >   if (offset >= si->max)
> >    goto unlock_out;
> >
> >   return si;
> > bad_nofile:
> >   pr_err("%s: %s%08lx\n", __func__, Bad_file, entry.val);
> > out:
> >   return NULL;
> > unlock_out:
> >   rcu_read_unlock();
> >   return NULL;
> > }
> > I guess the function "return si" without a rcu_read_unlock.
>
> Yes, but the caller is supposed to call put_swap_device() which
> calls rcu_read_unlock().  See commit eb085574a752.
I see, sorry for the mistake