Re: [PATCH] PCI: pcie: Call pm_runtime_no_callbacks() after device is registered

[Bjorn Helgaas <helgaas@kernel.org>]

On Mon, May 23, 2016 at 11:11:55AM +0300, Mika Westerberg wrote:
> Commit 0195d2813547 ("PCI: Add runtime PM support for PCIe ports") added
> call to pm_runtime_no_callbacks() for each port service device to prevent
> them exposing unnecessary runtime PM sysfs files. However, that function
> tries to acquire dev->power.lock which is not yet initialized.
> 
> This triggers following splat:
> 
>  BUG: spinlock bad magic on CPU#0, swapper/0/1
>   lock: 0xffff8801be2aa8e8, .magic: 00000000, .owner: <none>/-1, .owner_cpu: 0
>  CPU: 0 PID: 1 Comm: swapper/0 Not tainted 4.6.0+ #820
>   0000000000000000 ffff8801beb97be0 ffffffff812cf42d 0000000000000000
>   ffff8801be2aa8e8 ffff8801beb97c00 ffffffff8109ee58 ffff8801be2aa8e8
>   ffff8801be2aa8e8 ffff8801beb97c30 ffffffff8109efd9 ffff8801be2aa8e8
>  Call Trace:
>   [<ffffffff812cf42d>] dump_stack+0x4f/0x72
>   [<ffffffff8109ee58>] spin_dump+0x78/0xc0
>   [<ffffffff8109efd9>] do_raw_spin_lock+0xf9/0x150
>   [<ffffffff81674e10>] _raw_spin_lock_irq+0x20/0x30
>   [<ffffffff813d738e>] pm_runtime_no_callbacks+0x1e/0x40
>   [<ffffffff81322cad>] pcie_port_device_register+0x1fd/0x4e0
>   [<ffffffff813232f8>] pcie_portdrv_probe+0x38/0xa0
>   [<ffffffff81314fb5>] local_pci_probe+0x45/0xa0
>   [<ffffffff81315fe0>] ? pci_match_device+0xe0/0x110
>   [<ffffffff813163ab>] pci_device_probe+0xdb/0x130
>   [<ffffffff813ccefc>] driver_probe_device+0x22c/0x440
>   [<ffffffff813cd1e1>] __driver_attach+0xd1/0xf0
>   [<ffffffff813cd110>] ? driver_probe_device+0x440/0x440
>   [<ffffffff813caab4>] bus_for_each_dev+0x64/0xa0
>   [<ffffffff813cc60e>] driver_attach+0x1e/0x20
>   [<ffffffff813cc0cb>] bus_add_driver+0x1eb/0x280
>   [<ffffffff81d36cdc>] ? pcie_port_setup+0x7c/0x7c
>   [<ffffffff813cdb90>] driver_register+0x60/0xe0
>   [<ffffffff813148e0>] __pci_register_driver+0x60/0x70
>   [<ffffffff81d36d3f>] pcie_portdrv_init+0x63/0x75
>   [<ffffffff810003db>] do_one_initcall+0xab/0x1c0
>   [<ffffffff81cff083>] kernel_init_freeable+0x153/0x1d9
>   [<ffffffff8166dfce>] kernel_init+0xe/0x100
>   [<ffffffff81675612>] ret_from_fork+0x22/0x40
>   [<ffffffff8166dfc0>] ? rest_init+0x90/0x90
> 
> Fix this by calling pm_runtime_no_callbacks() after device_register() just
> like other buses, like I2C is doing already.
> 
> Reported-by: Valdis Kletnieks <valdis.kletnieks@vt.edu>
> Tested-by: Valdis Kletnieks <valdis.kletnieks@vt.edu>
> Suggested-by: Lukas Wunner <lukas@wunner.de>
> Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>

I think this is a bugfix for "PCI: Add runtime PM support for PCIe
ports", so I folded this into that patch since it hasn't been merged
yet.  Is that the right place for it?

> ---
>  drivers/pci/pcie/portdrv_core.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/pci/pcie/portdrv_core.c b/drivers/pci/pcie/portdrv_core.c
> index 65b1a624826b..97927dfbbf5f 100644
> --- a/drivers/pci/pcie/portdrv_core.c
> +++ b/drivers/pci/pcie/portdrv_core.c
> @@ -344,7 +344,6 @@ static int pcie_device_init(struct pci_dev *pdev, int service, int irq)
>  		     get_descriptor_id(pci_pcie_type(pdev), service));
>  	device->parent = &pdev->dev;
>  	device_enable_async_suspend(device);
> -	pm_runtime_no_callbacks(device);
>  
>  	retval = device_register(device);
>  	if (retval) {
> @@ -352,6 +351,8 @@ static int pcie_device_init(struct pci_dev *pdev, int service, int irq)
>  		return retval;
>  	}
>  
> +	pm_runtime_no_callbacks(device);
> +
>  	return 0;
>  }
>  
> -- 
> 2.8.1
>