On Thu, Oct 29, 2020 at 2:27 AM Qian Cai <c...@redhat.com> wrote:
>
> Lockdep complains that a possible deadlock below in
> eeh_addr_cache_show() because it is acquiring a lock with IRQ enabled,
> but eeh_addr_cache_insert_dev() needs to acquire the same lock with IRQ
> disabled. Let's just make eeh_addr_cache_show() acquire the lock with
> IRQ disabled as well.
>
> CPU0 CPU1
> ---- ----
> lock(&pci_io_addr_cache_root.piar_lock);
> local_irq_disable();
> lock(&tp->lock);
> lock(&pci_io_addr_cache_root.piar_lock);
> <Interrupt>
> lock(&tp->lock);
>
> *** DEADLOCK ***
>
> lock_acquire+0x140/0x5f0
> _raw_spin_lock_irqsave+0x64/0xb0
> eeh_addr_cache_insert_dev+0x48/0x390
> eeh_probe_device+0xb8/0x1a0
> pnv_pcibios_bus_add_device+0x3c/0x80
> pcibios_bus_add_device+0x118/0x290
> pci_bus_add_device+0x28/0xe0
> pci_bus_add_devices+0x54/0xb0
> pcibios_init+0xc4/0x124
> do_one_initcall+0xac/0x528
> kernel_init_freeable+0x35c/0x3fc
> kernel_init+0x24/0x148
> ret_from_kernel_thread+0x5c/0x80
>
> lock_acquire+0x140/0x5f0
> _raw_spin_lock+0x4c/0x70
> eeh_addr_cache_show+0x38/0x110
> seq_read+0x1a0/0x660
> vfs_read+0xc8/0x1f0
> ksys_read+0x74/0x130
> system_call_exception+0xf8/0x1d0
> system_call_common+0xe8/0x218
>
> Fixes: 5ca85ae6318d ("powerpc/eeh_cache: Add a way to dump the EEH address
> cache")
> Signed-off-by: Qian Cai <c...@redhat.com>
Good catch,
Reviewed-by: Oliver O'Halloran <ooh...@gmail.com>
