Re: [PATCH v2 14/17] resource: Move devmem revoke code to resource framework

Jason Gunthorpe
2020-10-09T12:31:16Z

On Fri, Oct 09, 2020 at 09:59:31AM +0200, Daniel Vetter wrote:

> +struct address_space *iomem_get_mapping(void)
> +{
> + return iomem_inode->i_mapping;

This should pair an acquire with the release below

> + /*
> + * Publish /dev/mem initialized.
> + * Pairs with smp_load_acquire() in revoke_iomem().
> + */
> + smp_store_release(&iomem_inode, inode);

However, this seems abnormal, initcalls rarely do this kind of stuff
with global data..

The kernel crashes if this fs_initcall is raced with
iomem_get_mapping() due to the unconditional dereference, so I think
it can be safely switched to a simple assignment.

Jason