On 24/05/2019 16:00, Gen Zhang wrote:
On Fri, May 24, 2019 at 03:47:34PM +0100, Jon Hunter wrote:
On 24/05/2019 15:33, Gen Zhang wrote:
On Fri, May 24, 2019 at 09:33:13AM +0100, Jon Hunter wrote:
On 24/05/2019 01:50, Gen Zhang wrote:
In tegra_wm9712_driver_probe(), 'machine->codec' is allocated by platform_device_alloc(). When it is NULL, function returns ENOMEM. However, 'machine' is allocated by devm_kzalloc() before this site. Thus we should free 'machine' before function ends to prevent memory leaking.
Memory allocated by devm_xxx() is automatically freed on failure so this is not correct.
Thanks for your comments, Jon. But after I examined the code, I am still confused about the usage of devm_kmalloc(). You can kindly refer to hisi_sas_debugfs_init() in drivers/scsi/hisi_sas/hisi_sas_main.c. And devm_kfree() is used to free a memory allocated by devm_kmalloc(). And I found other situations similar to this in other files.
So, I hope you can give me some guidance on this. Thanks!
Please refer to the devres documentation [0].
Cheers, Jon
[0] https://www.kernel.org/doc/Documentation/driver-model/devres.txt
-- nvpublic
Thanks for your reply. I figured out that devm_kmalloc will free the memory no matter fail or not. But I still want to ask why other codes as I above mentioned use devm_kfree() to free memory allocated by devm_kmalloc(). If the memory is automatically freed, is this devm_kfee() redundant codes that should be removed? Am I misunderstanding this again or it is something else?
There could well be cases where you need to explicitly call devm_kfree(), but having a quick glance at the example above, I don't see why you would call devm_kfree() here and yes looks like that code could be simplified significantly. Notice that hisi_sas_debugfs_exit() does not free any memory as it is not necessary to explicitly do so.
Cheers Jon