linux-kernel - Re: [BUG] WARN_ON(!context) in drivers/pci/hotplug/acpiphp

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Date:	Fri, 11 Oct 2013 09:01:53 -0400
From:	Steven Rostedt <rostedt@...dmis.org>
To:	"Rafael J. Wysocki" <rjw@...ysocki.net>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	LKML <linux-kernel@...r.kernel.org>,
	"Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
	Mika Westerberg <mika.westerberg@...ux.intel.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linux PCI <linux-pci@...r.kernel.org>,
	ACPI Devel Maling List <linux-acpi@...r.kernel.org>
Subject: Re: [BUG] WARN_ON(!context) in drivers/pci/hotplug/acpiphp_glue.c

On Fri, 11 Oct 2013 13:13:47 +0200
"Rafael J. Wysocki" <rjw@...ysocki.net> wrote:
> 
> From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> Subject: ACPI / hotplug / PCI: Accept coexistence with native PCIe hotplug
> 
> Allow ACPIPHP (ACPI-based PCI hotplug) to handle event signaling for
> devices that have already been claimed by the native PCIe hotplug
> (pciehp).
> 
> The ACPI hotplug events are essentially re-scan, remove and eject
> requests.  Re-scan and remove should work regardless, because they
> may be triggered by user space via sysfs and the ACPI eject (_EJ0)
> should work if the BIOS wants us to use it.  There may be an issue
> if the BIOS signals ACPI eject and wants us to use the native eject,
> but that doesn't work without this change anyway.
> 
> This change prevents the WARN_ON() in acpiphp_enumerate_slots() from
> triggering unnecessarily for bridges whose parents are managed by
> pciehp.
> 

Reported-by: Steven Rostedt <rostedt@...dmis.org>
Tested-by: Steven Rostedt <rostedt@...dmis.org>

-- Steve

> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> ---
>  drivers/pci/hotplug/acpiphp_glue.c |   32 ++++++++++++++++++++++++++------
>  1 file changed, 26 insertions(+), 6 deletions(-)
> 
> Index: linux-pm/drivers/pci/hotplug/acpiphp_glue.c
> ===================================================================
> --- linux-pm.orig/drivers/pci/hotplug/acpiphp_glue.c
> +++ linux-pm/drivers/pci/hotplug/acpiphp_glue.c
> @@ -259,6 +259,31 @@ static void acpiphp_dock_release(void *d
>  	put_bridge(context->func.parent);
>  }
>  
> +/**
> + * slot_should_be_exposed - Check whether or not to expose a slot to userland.
> + * @bridge: ACPIPHP bridge the slot belongs to.
> + * @handle: ACPI handle of a device in the slot.
> + */
> +static inline bool slot_should_be_exposed(struct acpiphp_bridge *bridge,
> +					  acpi_handle handle)
> +{
> +	struct pci_bus *pbus = bridge->pci_bus;
> +	struct pci_dev *pdev = bridge->pci_dev;
> +
> +	/*
> +	 * Do not expose slots whose bridges are managed by pciehp, because they
> +	 * will be exposed to user space by the pciehp driver.
> +	 */
> +	if (pdev && device_is_managed_by_native_pciehp(pdev))
> +		return false;
> +
> +	/*
> +	 * Expose slots for devices with either _EJ0 or _RMV and for devices
> +	 * on docking stations.
> +	 */
> +	return acpi_pci_check_ejectable(pbus, handle) || is_dock_device(handle);
> +}
> +
>  /* callback routine to register each ACPI PCI slot object */
>  static acpi_status register_slot(acpi_handle handle, u32 lvl, void *data,
>  				 void **rv)
> @@ -271,12 +296,8 @@ static acpi_status register_slot(acpi_ha
>  	unsigned long long adr;
>  	int device, function;
>  	struct pci_bus *pbus = bridge->pci_bus;
> -	struct pci_dev *pdev = bridge->pci_dev;
>  	u32 val;
>  
> -	if (pdev && device_is_managed_by_native_pciehp(pdev))
> -		return AE_OK;
> -
>  	status = acpi_evaluate_integer(handle, "_ADR", NULL, &adr);
>  	if (ACPI_FAILURE(status)) {
>  		acpi_handle_warn(handle, "can't evaluate _ADR (%#x)\n", status);
> @@ -325,8 +346,7 @@ static acpi_status register_slot(acpi_ha
>  
>  	list_add_tail(&slot->node, &bridge->slots);
>  
> -	/* Register slots for ejectable funtions only. */
> -	if (acpi_pci_check_ejectable(pbus, handle)  || is_dock_device(handle)) {
> +	if (slot_should_be_exposed(bridge, handle)) {
>  		unsigned long long sun;
>  		int retval;
>  

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