Re: [PATCH v4 1/2] mm/memory-failure: Use a mutex to avoid memory_failure() races

[Aili Yao]

On Tue, 27 Apr 2021 15:29:52 +0900
Naoya Horiguchi <nao.horiguchi@xxxxxxxxx> wrote:

> From: Tony Luck <tony.luck@xxxxxxxxx>
> 
> There can be races when multiple CPUs consume poison from the same
> page. The first into memory_failure() atomically sets the HWPoison
> page flag and begins hunting for tasks that map this page. Eventually
> it invalidates those mappings and may send a SIGBUS to the affected
> tasks.
> 
> But while all that work is going on, other CPUs see a "success"
> return code from memory_failure() and so they believe the error
> has been handled and continue executing.
> 
> Fix by wrapping most of the internal parts of memory_failure() in
> a mutex.
> 
> Signed-off-by: Tony Luck <tony.luck@xxxxxxxxx>
> Signed-off-by: Naoya Horiguchi <naoya.horiguchi@xxxxxxx>
> Reviewed-by: Borislav Petkov <bp@xxxxxxx>

Sorry to interrupt, I just thought one thing:

This mutex seems not been bind to the error page, will there be some core case
like test code or multi-poison case whick will break this mutex?

Thanks!
Aili Yao