From: Lin Ma linma@zju.edu.cn

The commit 6faee3d4ee8b ("igb: Add lock to avoid data race") adds rtnl_lock to eliminate a false data race shown below

(FREE from device detaching) | (USE from netdev core) igb_remove | igb_ndo_get_vf_config igb_disable_sriov | vf >= adapter->vfs_allocated_count? kfree(adapter->vf_data) | adapter->vfs_allocated_count = 0 | | memcpy(... adapter->vf_data[vf]

The above race will never happen and the extra rtnl_lock causes deadlock below

[ 141.420169] <TASK> [ 141.420672] __schedule+0x2dd/0x840 [ 141.421427] schedule+0x50/0xc0 [ 141.422041] schedule_preempt_disabled+0x11/0x20 [ 141.422678] __mutex_lock.isra.13+0x431/0x6b0 [ 141.423324] unregister_netdev+0xe/0x20 [ 141.423578] igbvf_remove+0x45/0xe0 [igbvf] [ 141.423791] pci_device_remove+0x36/0xb0 [ 141.423990] device_release_driver_internal+0xc1/0x160 [ 141.424270] pci_stop_bus_device+0x6d/0x90 [ 141.424507] pci_stop_and_remove_bus_device+0xe/0x20 [ 141.424789] pci_iov_remove_virtfn+0xba/0x120 [ 141.425452] sriov_disable+0x2f/0xf0 [ 141.425679] igb_disable_sriov+0x4e/0x100 [igb] [ 141.426353] igb_remove+0xa0/0x130 [igb] [ 141.426599] pci_device_remove+0x36/0xb0 [ 141.426796] device_release_driver_internal+0xc1/0x160 [ 141.427060] driver_detach+0x44/0x90 [ 141.427253] bus_remove_driver+0x55/0xe0 [ 141.427477] pci_unregister_driver+0x2a/0xa0 [ 141.428296] __x64_sys_delete_module+0x141/0x2b0 [ 141.429126] ? mntput_no_expire+0x4a/0x240 [ 141.429363] ? syscall_trace_enter.isra.19+0x126/0x1a0 [ 141.429653] do_syscall_64+0x5b/0x80 [ 141.429847] ? exit_to_user_mode_prepare+0x14d/0x1c0 [ 141.430109] ? syscall_exit_to_user_mode+0x12/0x30 [ 141.430849] ? do_syscall_64+0x67/0x80 [ 141.431083] ? syscall_exit_to_user_mode_prepare+0x183/0x1b0 [ 141.431770] ? syscall_exit_to_user_mode+0x12/0x30 [ 141.432482] ? do_syscall_64+0x67/0x80 [ 141.432714] ? exc_page_fault+0x64/0x140 [ 141.432911] entry_SYSCALL_64_after_hwframe+0x72/0xdc

Since the igb_disable_sriov() will call pci_disable_sriov() before releasing any resources, the netdev core will synchronize the cleanup to avoid any races. This patch removes the useless rtnl_(un)lock to guarantee correctness.

CC: stable@vger.kernel.org Fixes: 6faee3d4ee8b ("igb: Add lock to avoid data race") Reported-by: Corinna Vinschen vinschen@redhat.com Link: https://lore.kernel.org/intel-wired-lan/ZAcJvkEPqWeJHO2r@calimero.vinschen.d... Signed-off-by: Lin Ma linma@zju.edu.cn Tested-by: Corinna Vinschen vinschen@redhat.com Reviewed-by: Jacob Keller jacob.e.keller@intel.com Reviewed-by: Simon Horman simon.horman@corigine.com Tested-by: Rafal Romanowski rafal.romanowski@intel.com Signed-off-by: Tony Nguyen anthony.l.nguyen@intel.com --- drivers/net/ethernet/intel/igb/igb_main.c | 2 -- 1 file changed, 2 deletions(-)

diff --git a/drivers/net/ethernet/intel/igb/igb_main.c b/drivers/net/ethernet/intel/igb/igb_main.c index 03bc1e8af575..5532361b0e94 100644 --- a/drivers/net/ethernet/intel/igb/igb_main.c +++ b/drivers/net/ethernet/intel/igb/igb_main.c @@ -3863,9 +3863,7 @@ static void igb_remove(struct pci_dev *pdev) igb_release_hw_control(adapter);

#ifdef CONFIG_PCI_IOV - rtnl_lock(); igb_disable_sriov(pdev); - rtnl_unlock(); #endif

unregister_netdev(netdev);