On Sun, Feb 14, 2016 at 06:55:12AM +0200, Jarkko Sakkinen wrote: > On Fri, Feb 12, 2016 at 05:04:29PM -0700, Jason Gunthorpe wrote: > > This was missed during the struct device conversion, we > > need to hold a kref on the chip to make sure it isn't freed. > > > > Signed-off-by: Jason Gunthorpe <jguntho...@obsidianresearch.com> > > I'm bit confused about this patch. What is the regression if this > needs
The patch is simply totally broken, the placement of the get_device is wrong: > > @@ -53,6 +53,8 @@ struct tpm_chip *tpm_chip_find_get(int chip_num) > > chip = pos; > > break; > > } > > + > > + get_device(&chip->dev); It needs to be moved up two lines before the break, into the if statement. As for the urgency - today the tpm core relies on module locking to try and prevent tpm_chip_unregister from racing with stuff like the above. That is totally broken in modern kernels, but it is what the core tries to do. Within that framework the get/put are not needed because of the module locking. The only time these additional get/put do anything is when we are racing with tpm_unregister, but if we are racing with unregister then there are much bigger problems and things will crash anyhow. So, this patch is just a tiny step. The revised version of this patch with the rw_sem attempts to address the complete race. Jason
