Re: [PATCH v1] parisc: Use for_each_console() helper

[James Bottomley <James.Bottomley@HansenPartnership.com>]

On Fri, 2020-01-24 at 18:07 +0200, Andy Shevchenko wrote:
> Replace open coded single-linked list iteration loop with
> for_each_console()
> helper in use.
> 
> Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
> ---
>  arch/parisc/kernel/pdc_cons.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/parisc/kernel/pdc_cons.c
> b/arch/parisc/kernel/pdc_cons.c
> index 7ed404c60a9e..aa01448f377c 100644
> --- a/arch/parisc/kernel/pdc_cons.c
> +++ b/arch/parisc/kernel/pdc_cons.c
> @@ -259,8 +259,8 @@ void pdc_console_restart(void)
>  	if (console_drivers != NULL)
>  		pdc_cons.flags &= ~CON_PRINTBUFFER;
>  
> -	while ((console = console_drivers) != NULL)
> -		unregister_console(console_drivers);
> +	for_each_console(console)
> +		unregister_console(console);

This is wrong.  The old formulation iterates correctly in the face of
element removal.  for_each_console is defined:

#define for_each_console(con) \
	for (con = console_drivers; con != NULL; con = con->next)

So it's not safe for any iteration that alters the list elements.

James