Subject: Re: [PATCH] PSeries: Cancel RTAS event scan before firmware flash

From: Benjamin Herrenschmidt <[email-masked]>
Date: Fri, 23 Sep 2011 10:38:12 +1000

On Wed, 2011-09-21 at 15:59 +0530, Ravi K Nittala wrote:
> The RTAS firmware flash update is conducted using an RTAS call that is
> serialized by lock_rtas() which uses spin_lock. While the flash is in
> progress, rtasd performs scan for any RTAS events that are generated by
> the system. rtasd keeps scanning for the RTAS events generated on the
> machine. This is performed via workqueue mechanism. The rtas_event_scan()
> also uses an RTAS call to scan the events, eventually trying to acquire
> the spin_lock before issuing therequest.

Better. However:

> diff --git a/arch/powerpc/include/asm/rtas.h b/arch/powerpc/include/asm/rtas.h
> index 58625d1..b5cbd9f 100644
> --- a/arch/powerpc/include/asm/rtas.h
> +++ b/arch/powerpc/include/asm/rtas.h
> @@ -245,6 +245,10 @@ extern int early_init_dt_scan_rtas(unsigned long node,
>  
>  extern void pSeries_log_error(char *buf, unsigned int err_type, int fatal);
>  
> +#ifdef CONFIG_PPC_RTAS_DAEMON
> +extern bool rtas_cancel_event_scan(void);
> +#endif

The extern as such doesn't need an ifdef... however, you could avoid
this one:

 .../...
>  
> +#ifdef CONFIG_PPC_RTAS_DAEMON
> +	/*
> +	 * Just before starting the firmware flash, cancel the event scan work
> +	 * to avoid any soft lockup issues.
> +	 */
> +	rtas_cancel_event_scan();
> +#endif
> +

Here, by having the header contain instead:

#ifdef CONFIG_PPC_RTAS_DAEMON
extern void rtas_cancel_event_scan(void);
#else
static inline void rtas_cancel_event_scan(void) { }
#endif
 
Also note that I removed the bool, it's not useful since you don't
test it anyway.

>  	 * NOTE: the "first" block must be under 4GB, so we create
>  	 * an entry with no data blocks in the reserved buffer in
> diff --git a/arch/powerpc/kernel/rtasd.c b/arch/powerpc/kernel/rtasd.c
> index 481ef06..e8f03fa 100644
> --- a/arch/powerpc/kernel/rtasd.c
> +++ b/arch/powerpc/kernel/rtasd.c
> @@ -472,6 +472,12 @@ static void start_event_scan(void)
>  				 &event_scan_work, event_scan_delay);
>  }
>  
> +/* Cancel the rtas event scan work */
> +bool rtas_cancel_event_scan(void)
> +{
> +	return cancel_delayed_work_sync(&event_scan_work);
> +}

Finally, the above is missing an EXPORT_SYMBOL_GPL() since rtas
flash can be a module.

Cheers,
Ben.

>  static int __init rtas_init(void)
>  {
>  	struct proc_dir_entry *entry;