Re: [PATCH] arm_mpam: Release the mon_sel lock on mpam_save_mbwu_state() errors

[Ben Horgan <ben.horgan@arm.com>]

Hi Ping,

On 20/10/2026 12:48, Ping Li wrote:
> mpam_save_mbwu_state() takes the mon_sel lock at the top of each loop
> iteration, but the four error paths that return after failed
> MPAMF_MON_SEL register accesses do so without releasing it.
> 
> Take the lock with the conditional mon_sel_lock guard class instead,
> so all exit paths release it.
> 
> Fixes: a3a94c13c442 ("arm_mpam: propagate MSC access errors for state saving function")
> Signed-off-by: Ping Li <leeonion.muyu@gmail.com>

Thanks for this. Looks like this was a result of the conflict between the MPAM-Fb series and my
minor fixes series.

Reviewed-by: Ben Horgan <ben.horgan@arm.com>

Cheers,

Ben

> ---
>  drivers/resctrl/mpam_devices.c | 12 +++++-------
>  1 file changed, 5 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/resctrl/mpam_devices.c b/drivers/resctrl/mpam_devices.c
> index 48adc49b833c..c067b6d57d71 100644
> --- a/drivers/resctrl/mpam_devices.c
> +++ b/drivers/resctrl/mpam_devices.c
> @@ -2037,8 +2037,10 @@ static int mpam_save_mbwu_state(void *arg)
>  	struct mpam_class *class = ris->vmsc->comp->class;
>  
>  	for (i = 0; i < ris->props.num_mbwu_mon; i++) {
> -		if (WARN_ON_ONCE(!mpam_mon_sel_lock(msc)))
> -			return -EIO;
> +		ACQUIRE(mon_sel_lock, guard)(msc);
> +		ret = ACQUIRE_ERR(mon_sel_lock, &guard);
> +		if (ret)
> +			return ret;
>  
>  		mbwu_state = &ris->mbwu_state[i];
>  		cfg = &mbwu_state->cfg;
> @@ -2061,10 +2063,8 @@ static int mpam_save_mbwu_state(void *arg)
>  		cfg->partid = FIELD_GET(MSMON_CFG_x_FLT_PARTID, cur_flt);
>  		mbwu_state->enabled = FIELD_GET(MSMON_CFG_x_CTL_EN, cur_ctl);
>  
> -		if (!mbwu_state->enabled) {
> -			mpam_mon_sel_unlock(msc);
> +		if (!mbwu_state->enabled)
>  			continue;
> -		}
>  
>  		val = 0;
>  		mbwu_arg = (struct mon_read) {
> @@ -2088,8 +2088,6 @@ static int mpam_save_mbwu_state(void *arg)
>  		ret = mpam_write_monsel_reg(msc, CFG_MBWU_CTL, 0);
>  		if (ret)
>  			return ret;
> -
> -		mpam_mon_sel_unlock(msc);
>  	}
>  
>  	return 0;
> 
> base-commit: 8ea457f746d915d55f78b43d33b1cd618f3d93ad