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

[Subrata Modak <subrata@linux.vnet.ibm.com>]

Also,

On Tue, 2011-10-04 at 13:19 +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 the request.
> 
> The flash update takes a while to complete and during this time, any other
> RTAS call has to wait. In this case, rtas_event_scan() waits for a long time
> on the spin_lock resulting in a soft lockup.
> 
> Fix: Just before the flash update is performed, the queued rtas_event_scan()
> work item is cancelled from the work queue so that there is no other RTAS
> call issued while the flash is in progress. After the flash completes, the
> system reboots and the rtas_event_scan() is rescheduled.
> 
> Signed-off-by: Suzuki Poulose <suzuki@in.ibm.com>
> Signed-off-by: Ravi Nittala <ravi.nittala@in.ibm.com>

Reported-by: Divya Vikas <divya.vikas@in.ibm.com>

Regards--
Subrata

> 
> ---
>  arch/powerpc/include/asm/rtas.h  |    6 ++++++
>  arch/powerpc/kernel/rtas_flash.c |    6 ++++++
>  arch/powerpc/kernel/rtasd.c      |    7 +++++++
>  3 files changed, 19 insertions(+), 0 deletions(-)
> 
> diff --git a/arch/powerpc/include/asm/rtas.h b/arch/powerpc/include/asm/rtas.h
> index 58625d1..754723b 100644
> --- a/arch/powerpc/include/asm/rtas.h
> +++ b/arch/powerpc/include/asm/rtas.h
> @@ -245,6 +245,12 @@ 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 void rtas_cancel_event_scan(void);
> +#else
> +static inline void rtas_cancel_event_scan(void) { }
> +#endif
> +
>  /* Error types logged.  */
>  #define ERR_FLAG_ALREADY_LOGGED	0x0
>  #define ERR_FLAG_BOOT		0x1 	/* log was pulled from NVRAM on boot */
> diff --git a/arch/powerpc/kernel/rtas_flash.c b/arch/powerpc/kernel/rtas_flash.c
> index e037c74..4174b4b 100644
> --- a/arch/powerpc/kernel/rtas_flash.c
> +++ b/arch/powerpc/kernel/rtas_flash.c
> @@ -568,6 +568,12 @@ static void rtas_flash_firmware(int reboot_type)
>  	}
> 
>  	/*
> +	 * Just before starting the firmware flash, cancel the event scan work
> +	 * to avoid any soft lockup issues.
> +	 */
> +	rtas_cancel_event_scan();
> +
> +	/*
>  	 * NOTE: the "first" block must be under 4GB, so we create
>  	 * an entry with no data blocks in the reserved buffer in
>  	 * the kernel data segment.
> diff --git a/arch/powerpc/kernel/rtasd.c b/arch/powerpc/kernel/rtasd.c
> index 481ef06..1045ff4 100644
> --- a/arch/powerpc/kernel/rtasd.c
> +++ b/arch/powerpc/kernel/rtasd.c
> @@ -472,6 +472,13 @@ static void start_event_scan(void)
>  				 &event_scan_work, event_scan_delay);
>  }
> 
> +/* Cancel the rtas event scan work */
> +void rtas_cancel_event_scan(void)
> +{
> +	cancel_delayed_work_sync(&event_scan_work);
> +}
> +EXPORT_SYMBOL_GPL(rtas_cancel_event_scan);
> +
>  static int __init rtas_init(void)
>  {
>  	struct proc_dir_entry *entry;
>