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    SubjectRe: [PATCH v2] iwlwifi: don't call netif_napi_add() with rxq->lock held (was Re: Lockdep warning in iwl_pcie_rx_handle())
    Date
    On Tue, 2021-03-02 at 11:34 +0100, Jiri Kosina wrote:
    > From: Jiri Kosina <jkosina@suse.cz>
    >
    > 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@suse.cz>
    > ---
    >
    > v1->v2: Previous patch was not refreshed against current code-base, sorry.
    >
    >  drivers/net/wireless/intel/iwlwifi/pcie/rx.c | 3 ++-
    >  1 file changed, 2 insertions(+), 1 deletion(-)


    Thanks, Jiri! Let's take your patch since you already sent it out.

    Kalle, can you please take this directly to wireless-drivers.git?

    Acked-by: Luca Coelho <luciano.coelho@intel.com>

    --
    Cheers,
    Luca.
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