[Skiboot] [PATCH] FSP: Fix poller lock issue

[Ananth N Mavinakayanahalli]

On Sun, Mar 08, 2015 at 03:19:41PM +0530, Vasant Hegde wrote:
> This patch attempts to fix "poller lock issue" by removing
> opal_run_pollers function call from fsp_sync_msg.
> 
> sample log:
> ----------
> [4130907342,3] Running pollers with lock held !
> CPU 08b0 Backtrace:
>  S: 0000000033cc3990 R: 0000000030013520   .backtrace+0x2c
>  S: 0000000033cc3a20 R: 0000000030017d9c   .opal_run_pollers+0x44
>  S: 0000000033cc3aa0 R: 0000000030045f04   .fsp_sync_msg+0x40
>  S: 0000000033cc3b30 R: 0000000030047840   .fsp_fetch_data+0x138
>  S: 0000000033cc3c20 R: 0000000030021204   .hservices_lid_preload+0x148
>  S: 0000000033cc3d10 R: 0000000030058038   .ibm_fsp_init+0xe4
>  S: 0000000033cc3dc0 R: 0000000030058df8   .firenze_init+0x18
>  S: 0000000033cc3e30 R: 00000000300141a4   .main_cpu_entry+0x3e0
>  S: 0000000033cc3f00 R: 0000000030002534   boot_entry+0x18c
> 
> Signed-off-by: Vasant Hegde <hegdevasant at linux.vnet.ibm.com>
> 
> ---
> Ben, Stewart,
>   Presently we have two places (fsp_fetch_data & capp_lid_download) where
>   we held lock and make opal_run_pollers call (via fsp_sync_msg).
> 
>   Earlier we had replaced __fsp_poll with opal_run_pollers (commit 488dc8a3).
>   But I think its fine just to call __fsp_poll here. This seems to be working.
>   But needs to be reviewed before merging.
> 
>   I tried other alternative approach we discussed earlier. (introduce queue in
>   fsp_fetch_data). This requies quite a bit of work in callback function.

This explanation needs to go in the commit message.

> ---
>  hw/fsp/fsp.c |    5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/hw/fsp/fsp.c b/hw/fsp/fsp.c
> index e57c611..5fbc33f 100644
> --- a/hw/fsp/fsp.c
> +++ b/hw/fsp/fsp.c
> @@ -1663,7 +1663,10 @@ int fsp_sync_msg(struct fsp_msg *msg, bool autofree)
>  
>  	while(fsp_msg_busy(msg)) {
>  		cpu_relax();
> -		opal_run_pollers();
> +		lock(&fsp_lock);
> +		__fsp_poll(false);
> +		unlock(&fsp_lock);

You could just use fsp_opal_poll() instead.

Ananth