RE: [RFC] eal: add bus cleanup to eal cleanup

["Morten Brørup" <mb@smartsharesystems.com>]

> From: Kevin Laatz [mailto:kevin.laatz@intel.com]
> Sent: Tuesday, 19 April 2022 18.15
> 
> During EAL init, all buses are probed and the devices found are
> initialized. On eal_cleanup(), the inverse does not happen, meaning any
> allocated memory and other configuration will not be cleaned up
> appropriately on exit.
> 
> Currently, in order for device cleanup to take place, applications must
> call the driver-relevant functions to ensure proper cleanup is done
> before
> the application exits. Since initialization occurs for all devices on
> the
> bus, not just the devices used by an application, it requires a)
> application awareness of all bus devices that could have been probed on
> the
> system, and b) code duplication across applications to ensure cleanup
> is
> performed. An example of this is rte_eth_dev_close() which is commonly
> used
> across the example applications.
> 
> This RFC proposes adding bus cleanup to the eal_cleanup() to make EAL's
> init/exit more symmetrical, ensuring all bus devices are cleaned up
> appropriately without the application needing to be aware of all bus
> types
> that may have been probed during initialization.
> 
> Contained in this RFC are the changes required to perform cleanup for
> devices on the PCI bus during eal_cleanup(). This can be expanded in
> subsequent versions if these changes are desired. There would be an ask
> for
> bus maintainers to add the relevant cleanup for their buses since they
> have
> the domain expertise.
> 
> Signed-off-by: Kevin Laatz <kevin.laatz@intel.com>
> ---

[...]

> +		RTE_LOG(INFO, EAL,
> +				"Clean up PCI driver: %s (%x:%x) device:
> "PCI_PRI_FMT" (socket %i)\n",
> +				drv->driver.name, dev->id.vendor_id, dev-
> >id.device_id,
> +				loc->domain, loc->bus, loc->devid, loc-
> >function,
> +				dev->device.numa_node);

I agree with Stephen, this message might as well be DEBUG level. You could argue for symmetry: If the "alloc" message during startup is INFO level, it makes sense using INFO level for the "free" message during cleanup too. However, the message probably has far lower information value during cleanup (because this driver cleanup is expected to happen), so I would degrade it to DEBUG level. Symmetry is not always the strongest argument. I have no strong preference, so I'll leave it up to you, Kevin.

[...]

> @@ -263,6 +275,7 @@ struct rte_bus {
>  	const char *name;            /**< Name of the bus */
>  	rte_bus_scan_t scan;         /**< Scan for devices attached to
> bus */
>  	rte_bus_probe_t probe;       /**< Probe devices on bus */
> +	rte_bus_cleanup_t cleanup;   /**< Cleanup devices on bus */
>  	rte_bus_find_device_t find_device; /**< Find a device on the bus
> */
>  	rte_bus_plug_t plug;         /**< Probe single device for drivers
> */
>  	rte_bus_unplug_t unplug;     /**< Remove single device from
> driver */

Have you considered if modifying the rte_bus structure in /lib/eal/include/rte_bus.h breaks the ABI or not?


Overall, this patch is certainly a good idea!

On the condition that modifying the rte_bus structure does not break the ABI...

Acked-by: Morten Brørup <mb@smartsharesystems.com>