6.6-stable review patch. If anyone has any objections, please let me know.
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From: Jacob Keller jacob.e.keller@intel.com
[ Upstream commit c7d6cb96d5c33b5148f3dc76fcd30a9b8cd9e973 ]
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 jacob.e.keller@intel.com 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/... Reviewed-by: Przemek Kitszel przemyslaw.kitszel@intel.com Reviewed-by: Vitaly Lifshits vitaly.lifshits@intel.com Tested-by: Mor Bar-Gabay morx.bar.gabay@intel.com Signed-off-by: Tony Nguyen anthony.l.nguyen@intel.com Signed-off-by: Sasha Levin sashal@kernel.org --- 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 b6bb01a486d9d..a82af96e6bd12 100644 --- a/drivers/net/ethernet/intel/igc/igc_ptp.c +++ b/drivers/net/ethernet/intel/igc/igc_ptp.c @@ -1237,6 +1237,8 @@ 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) { @@ -1255,7 +1257,6 @@ 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);
@@ -1279,7 +1280,6 @@ 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. */ @@ -1296,5 +1296,7 @@ void igc_ptp_reset(struct igc_adapter *adapter) out: spin_unlock_irqrestore(&adapter->tmreg_lock, flags);
+ mutex_unlock(&adapter->ptm_lock); + wrfl(); }