Re: [RFC PATCH 08/10] openrisc: snapshot thread flags

[Stafford Horne <shorne@gmail.com>]

On Wed, Jun 09, 2021 at 01:19:59PM +0100, Mark Rutland wrote:
> Some thread flags can be set remotely, and so even when IRQs are
> disabled, the flags can change under our feet. Generally this is
> unlikely to cause a problem in practice, but it is somewhat unsound, and
> KCSAN will legitimately warn that there is a data race.
> 
> To avoid such issues, we should snapshot the flags prior to using them.
> Let's use the new helpers to do so on openrisc.
> 
> Signed-off-by: Mark Rutland <mark.rutland@arm.com>
> Cc: Jonas Bonn <jonas@southpole.se>
> Cc: Stafford Horne <shorne@gmail.com>
> Cc: Stefan Kristiansson <stefan.kristiansson@saunalahti.fi>
> ---
>  arch/openrisc/kernel/signal.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/arch/openrisc/kernel/signal.c b/arch/openrisc/kernel/signal.c
> index 1ebcff271096..a730a914c2b4 100644
> --- a/arch/openrisc/kernel/signal.c
> +++ b/arch/openrisc/kernel/signal.c
> @@ -315,7 +315,7 @@ do_work_pending(struct pt_regs *regs, unsigned int thread_flags, int syscall)
>  			}
>  		}
>  		local_irq_disable();
> -		thread_flags = current_thread_info()->flags;
> +		thread_flags = read_thread_flags();
>  	} while (thread_flags & _TIF_WORK_MASK);
>  	return 0;
>  }

This looks good to me.  As per patch 01/10 this adds a READ_ONCE around the
original flags read.

Acked-by: Stafford Horne <shorne@gmail.com>