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

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Message-ID: <ZyIIdTT-_pKC018c@calimero.vinschen.de>
Date: Wed, 30 Oct 2024 11:20:37 +0100
From: Corinna Vinschen <vinschen@...hat.com>
To: Chris H <christopher.s.hall@...el.com>
Cc: intel-wired-lan@...ts.osuosl.org, david.zage@...el.com,
	vinicius.gomes@...el.com, netdev@...r.kernel.org,
	rodrigo.cadore@...coustics.com
Subject: Re: [PATCH iwl-net v2 4/4] igc: Add lock preventing multiple
 simultaneous PTM transactions

Hi Chris,

Same question as in the v1 thread:

On Oct 23 02:30, Chris H wrote:
> From: Christopher S M Hall <christopher.s.hall@...el.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@...el.com>

I saw a former version of the patch which additionally added a mutex
lock/unlock in igc_ptp_reset() just before calling igc_ptm_trigger().
Is it safe to skip that?  igc_ptp_reset() is called from igc_reset()
which in turn is called from quite a few places.


Thanks,
Corinna





> ---
>  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);
>  
>  	adapter->tstamp_config.rx_filter = HWTSTAMP_FILTER_NONE;
>  	adapter->tstamp_config.tx_type = HWTSTAMP_TX_OFF;
> -- 
> 2.34.1