On 10/25/22 9:30 AM, Jason Gunthorpe wrote:
On Tue, Oct 25, 2022 at 09:29:09AM -0700, Paul E. McKenney wrote:
On Tue, Oct 25, 2022 at 01:00:02PM -0300, Jason Gunthorpe wrote:
On Tue, Oct 25, 2022 at 08:24:20AM -0700, Yonghong Song wrote:
The current uverbs_api_ioctl_method definition:
struct uverbs_api_ioctl_method {
int(__rcu *handler)(struct uverbs_attr_bundle *attrs);
DECLARE_BITMAP(attr_mandatory, UVERBS_API_ATTR_BKEY_LEN);
...
};
The struct member 'handler' is marked with __rcu. But unless
the function body pointed by 'handler' is changing (e.g., jited)
during runtime, there is no need with __rcu.
Huh? This is a sparse marker, it says that the pointer must always be
loaded with rcu_dereference
It has nothing to do with JIT, this patch is not correct
OK, I will bite...
This is a pointer to a function. Given that this function's code is
generated at compile time, what sequence of changes is rcu_dereference()
protecting against?
Module unload. We set the value to NULL and then synchronize_rcu
before unloading the code it points at.
Okay. Thanks for explanation. I forgot the module unload case.
I will look at compiler side then.
Jason
