Re: [PATCH iwl-net v2 4/4] igc: Add lock preventing multiple simultaneous PTM transactions

[Tony Nguyen <anthony.l.nguyen@intel.com>]

On 10/22/2024 7:30 PM, Chris H wrote:
> From: Christopher S M Hall <christopher.s.hall@intel.com>
> 
> Add a mutex around the PTM transaction to prevent multiple transactors
> 
> Multiple processes try to initiate a PTM transaction, one or all may
> fail. This can be reproduced by running two instances of the
> following:
> 
> $ sudo phc2sys -O 0 -i tsn0 -m
> 
> PHC2SYS exits with:
> 
> "ioctl PTP_OFFSET_PRECISE: Connection timed out" when the PTM transaction
>   fails
> 
> Note: Normally two instance of PHC2SYS will not run, but one process
>   should not break another.
> 
> Fixes: a90ec8483732 ("igc: Add support for PTP getcrosststamp()")
> Signed-off-by: Christopher S M Hall <christopher.s.hall@intel.com>
> ---
>   drivers/net/ethernet/intel/igc/igc.h     |  1 +
>   drivers/net/ethernet/intel/igc/igc_ptp.c | 12 ++++++++++--
>   2 files changed, 11 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/net/ethernet/intel/igc/igc.h b/drivers/net/ethernet/intel/igc/igc.h
> index eac0f966e0e4..323db1e2be38 100644
> --- a/drivers/net/ethernet/intel/igc/igc.h
> +++ b/drivers/net/ethernet/intel/igc/igc.h
> @@ -319,6 +319,7 @@ struct igc_adapter {
>   	struct timespec64 prev_ptp_time; /* Pre-reset PTP clock */
>   	ktime_t ptp_reset_start; /* Reset time in clock mono */
>   	struct system_time_snapshot snapshot;
> +	struct mutex ptm_lock; /* Only allow one PTM transaction at a time */
>   
>   	char fw_version[32];
>   
> diff --git a/drivers/net/ethernet/intel/igc/igc_ptp.c b/drivers/net/ethernet/intel/igc/igc_ptp.c
> index fb885fcaa97c..4e1379b7d2ee 100644
> --- a/drivers/net/ethernet/intel/igc/igc_ptp.c
> +++ b/drivers/net/ethernet/intel/igc/igc_ptp.c
> @@ -1068,9 +1068,16 @@ static int igc_ptp_getcrosststamp(struct ptp_clock_info *ptp,
>   {
>   	struct igc_adapter *adapter = container_of(ptp, struct igc_adapter,
>   						   ptp_caps);
> +	int ret;
>   
> -	return get_device_system_crosststamp(igc_phc_get_syncdevicetime,
> -					     adapter, &adapter->snapshot, cts);
> +	/* This blocks until any in progress PTM transactions complete */
> +	mutex_lock(&adapter->ptm_lock);
> +
> +	ret = get_device_system_crosststamp(igc_phc_get_syncdevicetime,
> +					    adapter, &adapter->snapshot, cts);
> +	mutex_unlock(&adapter->ptm_lock);
> +
> +	return ret;
>   }
>   
>   static int igc_ptp_getcyclesx64(struct ptp_clock_info *ptp,
> @@ -1169,6 +1176,7 @@ void igc_ptp_init(struct igc_adapter *adapter)
>   	spin_lock_init(&adapter->ptp_tx_lock);
>   	spin_lock_init(&adapter->free_timer_lock);
>   	spin_lock_init(&adapter->tmreg_lock);
> +	mutex_init(&adapter->ptm_lock);

I believe there should be a corresponding mutex_destroy()?

Thanks,
Tony

>   	adapter->tstamp_config.rx_filter = HWTSTAMP_FILTER_NONE;
>   	adapter->tstamp_config.tx_type = HWTSTAMP_TX_OFF;