Re: [PATCH v2] ring-buffer: Prevent inconsistent operation on cpu_buffer->resize_disabled

[Tze-nan Wu (吳澤南)]

Hi Bagas,

On Sun, 2023-04-09 at 19:30 +0700, Bagas Sanjaya wrote:
> 
> On 4/9/23 09:46, Tze-nan Wu wrote:
> > This issue can be reproduced by "echo 0 > trace" and hotplug cpu at
> > the
> > same time. After reproducing success, we can find out
> > buffer_size_kb
> > will not be functional anymore.
> > 
> 
> Do you mean disabling tracing while hotplugging CPU? Or disabling
> both
> tracing and hotplug CPU?
> 
  I mean disabling tracing while hotplugging CPU, sorry for the
confusion here.

> > This patch uses cpus_read_lock() to prevent cpu_online_mask being
> > changed
> > between two different "for_each_online_buffer_cpu".
> > 
> 
> "Use cpu_read_lock() to prevent ..."
> 
  Thanks for the suggestion 

> > Changes in v2:
> >   Use cpus_read_lock() instead of copying cpu_online_mask at the
> > entry of
> >   function
> > 
> 
  Since I change to fix the issue by using cpus_read_lock(), we don't
need a copy of cpu_online_mask anymore, hence the two warnings will not
meet in the v2 patch.

> To resolve kernel test robot warnings ([1] and [2])? Or have they
> been fixed?
> 
> [1]: 
> https://lore.kernel.org/stable/202304081615.eiaqpbV8-lkp@xxxxxxxxx/
> [2]: 
> https://lore.kernel.org/stable/202304082051.Dp50upfS-lkp@xxxxxxxxx/
> 
> Thanks.
> 
> --
> An old man doll... just what I always wanted! - Clara
>