Jiri Kosina <jikos@xxxxxxxxxx> wrote:
> From: Jiri Kosina <jkosina@xxxxxxx>
>
> We can't call netif_napi_add() with rxq-lock held, as there is a potential
> for deadlock as spotted by lockdep (see below). rxq->lock is not
> protecting anything over the netif_napi_add() codepath anyway, so let's
> drop it just before calling into NAPI.
>
> ========================================================
> WARNING: possible irq lock inversion dependency detected
> 5.12.0-rc1-00002-gbada49429032 #5 Not tainted
> --------------------------------------------------------
> irq/136-iwlwifi/565 just changed the state of lock:
> ffff89f28433b0b0 (&rxq->lock){+.-.}-{2:2}, at: iwl_pcie_rx_handle+0x7f/0x960 [iwlwifi]
> but this lock took another, SOFTIRQ-unsafe lock in the past:
> (napi_hash_lock){+.+.}-{2:2}
>
> and interrupts could create inverse lock ordering between them.
>
> other info that might help us debug this:
> Possible interrupt unsafe locking scenario:
>
> CPU0 CPU1
> ---- ----
> lock(napi_hash_lock);
> local_irq_disable();
> lock(&rxq->lock);
> lock(napi_hash_lock);
> <Interrupt>
> lock(&rxq->lock);
>
> *** DEADLOCK ***
>
> 1 lock held by irq/136-iwlwifi/565:
> #0: ffff89f2b1440170 (sync_cmd_lockdep_map){+.+.}-{0:0}, at: iwl_pcie_irq_handler+0x5/0xb30
>
> the shortest dependencies between 2nd lock and 1st lock:
> -> (napi_hash_lock){+.+.}-{2:2} {
> HARDIRQ-ON-W at:
> lock_acquire+0x277/0x3d0
> _raw_spin_lock+0x2c/0x40
> netif_napi_add+0x14b/0x270
> e1000_probe+0x2fe/0xee0 [e1000e]
> local_pci_probe+0x42/0x90
> pci_device_probe+0x10b/0x1c0
> really_probe+0xef/0x4b0
> driver_probe_device+0xde/0x150
> device_driver_attach+0x4f/0x60
> __driver_attach+0x9c/0x140
> bus_for_each_dev+0x79/0xc0
> bus_add_driver+0x18d/0x220
> driver_register+0x5b/0xf0
> do_one_initcall+0x5b/0x300
> do_init_module+0x5b/0x21c
> load_module+0x1dae/0x22c0
> __do_sys_finit_module+0xad/0x110
> do_syscall_64+0x33/0x80
> entry_SYSCALL_64_after_hwframe+0x44/0xae
> SOFTIRQ-ON-W at:
> lock_acquire+0x277/0x3d0
> _raw_spin_lock+0x2c/0x40
> netif_napi_add+0x14b/0x270
> e1000_probe+0x2fe/0xee0 [e1000e]
> local_pci_probe+0x42/0x90
> pci_device_probe+0x10b/0x1c0
> really_probe+0xef/0x4b0
> driver_probe_device+0xde/0x150
> device_driver_attach+0x4f/0x60
> __driver_attach+0x9c/0x140
> bus_for_each_dev+0x79/0xc0
> bus_add_driver+0x18d/0x220
> driver_register+0x5b/0xf0
> do_one_initcall+0x5b/0x300
> do_init_module+0x5b/0x21c
> load_module+0x1dae/0x22c0
> __do_sys_finit_module+0xad/0x110
> do_syscall_64+0x33/0x80
> entry_SYSCALL_64_after_hwframe+0x44/0xae
> INITIAL USE at:
> lock_acquire+0x277/0x3d0
> _raw_spin_lock+0x2c/0x40
> netif_napi_add+0x14b/0x270
> e1000_probe+0x2fe/0xee0 [e1000e]
> local_pci_probe+0x42/0x90
> pci_device_probe+0x10b/0x1c0
> really_probe+0xef/0x4b0
> driver_probe_device+0xde/0x150
> device_driver_attach+0x4f/0x60
> __driver_attach+0x9c/0x140
> bus_for_each_dev+0x79/0xc0
> bus_add_driver+0x18d/0x220
> driver_register+0x5b/0xf0
> do_one_initcall+0x5b/0x300
> do_init_module+0x5b/0x21c
> load_module+0x1dae/0x22c0
> __do_sys_finit_module+0xad/0x110
> do_syscall_64+0x33/0x80
> entry_SYSCALL_64_after_hwframe+0x44/0xae
> }
> ... key at: [<ffffffffae84ef38>] napi_hash_lock+0x18/0x40
> ... acquired at:
> _raw_spin_lock+0x2c/0x40
> netif_napi_add+0x14b/0x270
> _iwl_pcie_rx_init+0x1f4/0x710 [iwlwifi]
> iwl_pcie_rx_init+0x1b/0x3b0 [iwlwifi]
> iwl_trans_pcie_start_fw+0x2ac/0x6a0 [iwlwifi]
> iwl_mvm_load_ucode_wait_alive+0x116/0x460 [iwlmvm]
> iwl_run_init_mvm_ucode+0xa4/0x3a0 [iwlmvm]
> iwl_op_mode_mvm_start+0x9ed/0xbf0 [iwlmvm]
> _iwl_op_mode_start.isra.4+0x42/0x80 [iwlwifi]
> iwl_opmode_register+0x71/0xe0 [iwlwifi]
> iwl_mvm_init+0x34/0x1000 [iwlmvm]
> do_one_initcall+0x5b/0x300
> do_init_module+0x5b/0x21c
> load_module+0x1dae/0x22c0
> __do_sys_finit_module+0xad/0x110
> do_syscall_64+0x33/0x80
> entry_SYSCALL_64_after_hwframe+0x44/0xae
>
> [ ... lockdep output trimmed .... ]
>
> Fixes: 25edc8f259c7106 ("iwlwifi: pcie: properly implement NAPI")
> Signed-off-by: Jiri Kosina <jkosina@xxxxxxx>
> Acked-by: Luca Coelho <luciano.coelho@xxxxxxxxx>
Patch applied to wireless-drivers.git, thanks.
295d4cd82b01 iwlwifi: don't call netif_napi_add() with rxq->lock held (was Re: Lockdep warning in iwl_pcie_rx_handle())
--
https://patchwork.kernel.org/project/linux-wireless/patch/nycvar.YFH.7.76.2103021134060.12405@xxxxxxxxxxxxx/
https://wireless.wiki.kernel.org/en/developers/documentation/submittingpatches
