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

[Tony Nguyen]

On 10/22/2024 7:30 PM, Chris H wrote:

From: Christopher S M Hall <christopher.s.h...@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.h...@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;