netdev - [bug report] igc: add lock preventing multiple simultaneous PTM transactions

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Message-ID: <Z_-P-Hc1yxcw0lTB@stanley.mountain>
Date: Wed, 16 Apr 2025 14:09:44 +0300
From: Dan Carpenter <dan.carpenter@...aro.org>
To: Christopher S M Hall <christopher.s.hall@...el.com>
Cc: intel-wired-lan@...ts.osuosl.org, netdev@...r.kernel.org
Subject: [bug report] igc: add lock preventing multiple simultaneous PTM
 transactions

Hello Christopher S M Hall,

Commit 1a931c4f5e68 ("igc: add lock preventing multiple simultaneous
PTM transactions") from Apr 1, 2025 (linux-next), leads to the
following Smatch static checker warning:

	drivers/net/ethernet/intel/igc/igc_ptp.c:1311 igc_ptp_reset()
	warn: sleeping in atomic context

drivers/net/ethernet/intel/igc/igc_ptp.c
    1280 void igc_ptp_reset(struct igc_adapter *adapter)
    1281 {
    1282         struct igc_hw *hw = &adapter->hw;
    1283         u32 cycle_ctrl, ctrl, stat;
    1284         unsigned long flags;
    1285         u32 timadj;
    1286 
    1287         if (!(adapter->ptp_flags & IGC_PTP_ENABLED))
    1288                 return;
    1289 
    1290         /* reset the tstamp_config */
    1291         igc_ptp_set_timestamp_mode(adapter, &adapter->tstamp_config);
    1292 
    1293         spin_lock_irqsave(&adapter->tmreg_lock, flags);
                 ^^^^^^^^^^^^^^^^^
Holding a spin_lock

    1294 
    1295         switch (adapter->hw.mac.type) {
    1296         case igc_i225:
    1297                 timadj = rd32(IGC_TIMADJ);
    1298                 timadj |= IGC_TIMADJ_ADJUST_METH;
    1299                 wr32(IGC_TIMADJ, timadj);
    1300 
    1301                 wr32(IGC_TSAUXC, 0x0);
    1302                 wr32(IGC_TSSDP, 0x0);
    1303                 wr32(IGC_TSIM,
    1304                      IGC_TSICR_INTERRUPTS |
    1305                      (adapter->pps_sys_wrap_on ? IGC_TSICR_SYS_WRAP : 0));
    1306                 wr32(IGC_IMS, IGC_IMS_TS);
    1307 
    1308                 if (!igc_is_crosststamp_supported(adapter))
    1309                         break;
    1310 
--> 1311                 mutex_lock(&adapter->ptm_lock);
                         ^^^^^^^^^^
So we can't take a mutex.

    1312                 wr32(IGC_PCIE_DIG_DELAY, IGC_PCIE_DIG_DELAY_DEFAULT);
    1313                 wr32(IGC_PCIE_PHY_DELAY, IGC_PCIE_PHY_DELAY_DEFAULT);
    1314 
    1315                 cycle_ctrl = IGC_PTM_CYCLE_CTRL_CYC_TIME(IGC_PTM_CYC_TIME_DEFAULT);
    1316 
    1317                 wr32(IGC_PTM_CYCLE_CTRL, cycle_ctrl);
    1318 
    1319                 ctrl = IGC_PTM_CTRL_EN |
    1320                         IGC_PTM_CTRL_START_NOW |
    1321                         IGC_PTM_CTRL_SHRT_CYC(IGC_PTM_SHORT_CYC_DEFAULT) |
    1322                         IGC_PTM_CTRL_PTM_TO(IGC_PTM_TIMEOUT_DEFAULT);
    1323 
    1324                 wr32(IGC_PTM_CTRL, ctrl);
    1325 
    1326                 /* Force the first cycle to run. */
    1327                 igc_ptm_trigger(hw);
    1328 
    1329                 if (readx_poll_timeout_atomic(rd32, IGC_PTM_STAT, stat,
    1330                                               stat, IGC_PTM_STAT_SLEEP,
    1331                                               IGC_PTM_STAT_TIMEOUT))
    1332                         netdev_err(adapter->netdev, "Timeout reading IGC_PTM_STAT register\n");
    1333 
    1334                 igc_ptm_reset(hw);
    1335                 mutex_unlock(&adapter->ptm_lock);
    1336                 break;
    1337         default:
    1338                 /* No work to do. */
    1339                 goto out;
    1340         }
    1341 
    1342         /* Re-initialize the timer. */
    1343         if (hw->mac.type == igc_i225) {
    1344                 igc_ptp_time_restore(adapter);
    1345         } else {
    1346                 timecounter_init(&adapter->tc, &adapter->cc,
    1347                                  ktime_to_ns(ktime_get_real()));
    1348         }
    1349 out:
    1350         spin_unlock_irqrestore(&adapter->tmreg_lock, flags);
    1351 
    1352         wrfl();
    1353 }

regards,
dan carpenter