From c7d6cb96d5c33b5148f3dc76fcd30a9b8cd9e973 Mon Sep 17 00:00:00 2001 From: Jacob Keller Date: Tue, 22 Apr 2025 14:03:09 -0700 Subject: [PATCH] igc: fix lock order in igc_ptp_reset Commit 1a931c4f5e68 ("igc: add lock preventing multiple simultaneous PTM transactions") added a new mutex to protect concurrent PTM transactions. This lock is acquired in igc_ptp_reset() in order to ensure the PTM registers are properly disabled after a device reset. The flow where the lock is acquired already holds a spinlock, so acquiring a mutex leads to a sleep-while-locking bug, reported both by smatch, and the kernel test robot. The critical section in igc_ptp_reset() does correctly use the readx_poll_timeout_atomic variants, but the standard PTM flow uses regular sleeping variants. This makes converting the mutex to a spinlock a bit tricky. Instead, re-order the locking in igc_ptp_reset. Acquire the mutex first, and then the tmreg_lock spinlock. This is safe because there is no other ordering dependency on these locks, as this is the only place where both locks were acquired simultaneously. Indeed, any other flow acquiring locks in that order would be wrong regardless. Signed-off-by: Jacob Keller Fixes: 1a931c4f5e68 ("igc: add lock preventing multiple simultaneous PTM transactions") Link: https://lore.kernel.org/intel-wired-lan/Z_-P-Hc1yxcw0lTB@stanley.mountain/ Link: https://lore.kernel.org/intel-wired-lan/202504211511.f7738f5d-lkp@intel.com/T/#u Reviewed-by: Przemek Kitszel Reviewed-by: Vitaly Lifshits Tested-by: Mor Bar-Gabay Signed-off-by: Tony Nguyen --- drivers/net/ethernet/intel/igc/igc_ptp.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/drivers/net/ethernet/intel/igc/igc_ptp.c b/drivers/net/ethernet/intel/igc/igc_ptp.c index 612ed26a29c5..efc7b30e4211 100644 --- a/drivers/net/ethernet/intel/igc/igc_ptp.c +++ b/drivers/net/ethernet/intel/igc/igc_ptp.c @@ -1290,6 +1290,8 @@ void igc_ptp_reset(struct igc_adapter *adapter) /* reset the tstamp_config */ igc_ptp_set_timestamp_mode(adapter, &adapter->tstamp_config); + mutex_lock(&adapter->ptm_lock); + spin_lock_irqsave(&adapter->tmreg_lock, flags); switch (adapter->hw.mac.type) { @@ -1308,7 +1310,6 @@ void igc_ptp_reset(struct igc_adapter *adapter) if (!igc_is_crosststamp_supported(adapter)) break; - mutex_lock(&adapter->ptm_lock); wr32(IGC_PCIE_DIG_DELAY, IGC_PCIE_DIG_DELAY_DEFAULT); wr32(IGC_PCIE_PHY_DELAY, IGC_PCIE_PHY_DELAY_DEFAULT); @@ -1332,7 +1333,6 @@ void igc_ptp_reset(struct igc_adapter *adapter) netdev_err(adapter->netdev, "Timeout reading IGC_PTM_STAT register\n"); igc_ptm_reset(hw); - mutex_unlock(&adapter->ptm_lock); break; default: /* No work to do. */ @@ -1349,5 +1349,7 @@ void igc_ptp_reset(struct igc_adapter *adapter) out: spin_unlock_irqrestore(&adapter->tmreg_lock, flags); + mutex_unlock(&adapter->ptm_lock); + wrfl(); }