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

[Matthew Wilcox]

On Thu, Jul 22, 2021 at 04:57:57PM +0800, Zhouyi Zhou wrote:
> Thanks for reviewing,
> 
> What I have deduced from the dmesg  is:
> In function do_swap_page,
> after invoking
> 3385        si = get_swap_device(entry); /* rcu_read_lock */
> and before
> 3561    out:
> 3562        if (si)
> 3563            put_swap_device(si);
> The thread got scheduled out in
> 3454        locked = lock_page_or_retry(page, vma->vm_mm, vmf->flags);
> 
> I am only familiar with Linux RCU subsystem, hope mm people can solve our
> confusions.

I don't understamd why you're still talking.  The problem is understood.
You need to revert the unnecessary backport of 2799e77529c2 and
2efa33fc7f6e