[linux-yocto] [PATCH v5.2&v5.3] pci: octeontx2: Use a more lightweight API to get the root bus

[Bruce Ashfield]

On Mon, Oct 14, 2019 at 4:56 AM Kevin Hao <haokexin at gmail.com> wrote:
>
> In the current code, the API pci_get_domain_bus_and_slot() is used to
> get the root bus. But we would get the below call trace on rt kernel
> due to the spin_lock is used in the klist.
>   BUG: sleeping function called from invalid context at kernel/locking/rtmutex.c:968
>   in_atomic(): 1, irqs_disabled(): 128, pid: 1, name: swapper/0
>   3 locks held by swapper/0/1:
>    #0: (____ptrval____) (per_cpu_ptr(&bh_lock.lock, cpu)){....}, at: __device_driver_lock+0x34/0x60
>    #1: (____ptrval____) (pci_lock){....}, at: pci_bus_write_config_word+0x40/0xa8
>    #2: (____ptrval____) (&k->k_lock){+.+.}, at: klist_next+0x24/0x110
>   irq event stamp: 1293008
>   hardirqs last  enabled at (1293007): [<ffff000010a3dd48>] _raw_spin_unlock_irqrestore+0xa8/0xb8
>   hardirqs last disabled at (1293008): [<ffff000010a3daa0>] _raw_spin_lock_irqsave+0x38/0x80
>   softirqs last  enabled at (1032902): [<ffff00001090bd74>] raw_unhash_sk+0x74/0xb0
>   softirqs last disabled at (1032891): [<ffff00001090bd00>] raw_unhash_sk+0x0/0xb0
>   Preemption disabled at:
>   [<ffff00001059a198>] pci_bus_write_config_word+0x40/0xa8
>   CPU: 8 PID: 1 Comm: swapper/0 Not tainted 5.2.20-rt9-yocto-preempt-rt+ #12
>   Hardware name: Marvell OcteonTX CN96XX board (DT)
>   Call trace:
>    dump_backtrace+0x0/0x140
>    show_stack+0x24/0x30
>    dump_stack+0xbc/0x104
>    ___might_sleep+0x16c/0x1d0
>    rt_spin_lock+0x64/0x78
>    klist_next+0x24/0x110
>    bus_find_device+0x70/0xe0
>    pci_get_dev_by_id+0x60/0x88
>    pci_get_domain_bus_and_slot+0x5c/0xb0
>    octeontx2_pem_config_write+0x84/0x3e0
>    pci_bus_write_config_word+0x64/0xa8
>    pci_write_config_word+0x44/0x68
>    pci_setup_device+0x214/0x718
>    pci_scan_single_device+0xb4/0xf8
>    pci_scan_slot+0x44/0x108
>    pci_scan_child_bus_extend+0x58/0x290
>    pci_scan_bridge_extend+0x350/0x4f8
>    pci_scan_child_bus_extend+0x1e4/0x290
>    pci_scan_root_bus_bridge+0x60/0xd0
>    pci_host_probe+0x20/0xb8
>    pci_host_common_probe+0xf4/0x1f0
>    octeontx2_pem_probe+0x2c/0x38
>    platform_drv_probe+0x58/0xa8
>    really_probe+0xe0/0x288
>    driver_probe_device+0x5c/0xf0
>    device_driver_attach+0x74/0x80
>    __driver_attach+0x64/0xe0
>    bus_for_each_dev+0x84/0xd8
>    driver_attach+0x30/0x40
>    bus_add_driver+0x190/0x1f0
>    driver_register+0x64/0x110
>    __platform_driver_register+0x54/0x60
>    octeontx2_pem_driver_init+0x20/0x28
>    do_one_initcall+0xa8/0x468
>    kernel_init_freeable+0x514/0x5b8
>    kernel_init+0x18/0x108
>    ret_from_fork+0x10/0x1c
>
> Actually we can use a more lightweight API to get the rootbus without
> acquiring any lock, then fix this issue.
>
> Signed-off-by: Kevin Hao <haokexin at gmail.com>
> ---
>
> Hi Bruce,
>
> Please help merge this to the following branches:
>
> linux-yocto:
>   v5.2/standard/cn96xx
>   v5.2/standard/preempt-rt/cn96xx

merged

>
> linux-yocto-dev:
>   standard/cn96xx

.. and merged. But I'm about a day away from replacing linux-yocto-dev
with v5.4-rc3, so be prepared that this will change shortly.

Bruce

>
>  drivers/pci/controller/pci-octeontx2-pem.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/pci/controller/pci-octeontx2-pem.c b/drivers/pci/controller/pci-octeontx2-pem.c
> index 90b5537e8cdb..1e14dc065322 100644
> --- a/drivers/pci/controller/pci-octeontx2-pem.c
> +++ b/drivers/pci/controller/pci-octeontx2-pem.c
> @@ -335,10 +335,10 @@ static void octeontx2_be_workaround_init(struct pci_bus *bus)
>  static void octeontx2_be_workaround(struct pci_bus *bus, int where,
>                                     int size, u32 val)
>  {
> -       struct pci_dev *rc;
> +       struct pci_host_bridge *rc;
>         u32 reg, be = 0;
>
> -       rc = pci_get_domain_bus_and_slot(pci_domain_nr(bus), 0, 0);
> +       rc = pci_find_host_bridge(bus);
>
>         /* Setup RAS to inject one error */
>         octeontx2_be_workaround_init(rc->bus);
> --
> 2.14.4
>


-- 
- Thou shalt not follow the NULL pointer, for chaos and madness await
thee at its end
- "Use the force Harry" - Gandalf, Star Trek II