On Mon, 1 Mar 2021, Johannes Berg wrote: > > I am getting the splat below with Linus' tree as of today (5.11-rc1, > > fe07bfda2fb). I haven't started to look into the code yet, but apparently > > this has been already reported by Heiner here: > > > > https://www.spinics.net/lists/linux-wireless/msg208353.html > > > > so before I start digging deep into it (the previous kernel this > > particular machine had is 5.9, so I'd rather avoid lenghty bisect for now > > in case someone has already looked into it and has ideas where the problem > > is), I thought I'd ask whether this has been root-caused elsewhere > > already. > > Yeah, I'm pretty sure we have a fix for this, though I'm not sure right > now where it is in the pipeline. > > It's called "iwlwifi: pcie: don't add NAPI under rxq->lock" but right > now I can't find it in any of the public archives. I was not able to find that patch anywhere indeed, but in the meantime I fixed it by the patch below. Please consider merging either of the fixes. Also I am still seeing WARNING: CPU: 2 PID: 1138 at kernel/softirq.c:178 __local_bh_enable_ip+0xa5/0xf0 on the [ 21.902173] iwl_pcie_enqueue_hcmd+0x5d9/0xa00 [iwlwifi] [ 21.906445] iwl_trans_txq_send_hcmd+0x6c/0x430 [iwlwifi] [ 21.910757] iwl_trans_send_cmd+0x88/0x170 [iwlwifi] [ 21.915074] ? lock_acquire+0x277/0x3d0 [ 21.919327] iwl_mvm_send_cmd+0x32/0x80 [iwlmvm] [ 21.923616] iwl_mvm_led_set+0xc2/0xe0 [iwlmvm] codepath, but I'll look into it separately. From: Jiri Kosina <jkosina@xxxxxxx> Subject: [PATCH] iwlwifi: don't call netif_napi_add() with rxq->lock held 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> --- drivers/net/wireless/intel/iwlwifi/pcie/rx.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/drivers/net/wireless/intel/iwlwifi/pcie/rx.c b/drivers/net/wireless/intel/iwlwifi/pcie/rx.c index 1bccaa034284..6262dd9043aa 100644 --- a/drivers/net/wireless/intel/iwlwifi/pcie/rx.c +++ b/drivers/net/wireless/intel/iwlwifi/pcie/rx.c @@ -1063,11 +1063,12 @@ static int _iwl_pcie_rx_init(struct iwl_trans *trans) iwl_pcie_rx_init_rxb_lists(rxq); + spin_unlock_bh(&rxq->lock); + if (!rxq->napi.poll) netif_napi_add(&trans_pcie->napi_dev, &rxq->napi, iwl_pcie_dummy_napi_poll, 64); - spin_unlock_bh(&rxq->lock); } /* move the pool to the default queue and allocator ownerships */ -- Jiri Kosina SUSE Labs
