On Wed, Dec 05, 2018 at 07:10:52AM -0800, Dennis Dalessandro wrote:
> +#include <linux/types.h>
> +#include <rdma/ib_user_verbs.h>
> +#ifndef RDMA_ATOMIC_UAPI
> +#define RDMA_ATOMIC_UAPI(_type, _name) _type _name
> +#endif
> +/*
> + * This structure is used to contain the head pointer, tail pointer,
> + * and completion queue entries as a single memory allocation so
> + * it can be mmap'ed into user space.
> + */
> +struct rvt_cq_wc {
> + /* index of next entry to fill */
> + RDMA_ATOMIC_UAPI(u32, head);
> + /* index of next ib_poll_cq() entry */
> + RDMA_ATOMIC_UAPI(u32, tail);
I went and looked at all the readers of these variables, and they are
all missing a READ_ONCE (ie the kernel version of
atomic_load(relaxed))
I think you should change the definition to be:
#define RDMA_ATOMIC_UAPI(_type, _name) struct {_type atomic_val;} _name
And then add a kernel function
#define RDMA_READ_UAPI_ATOMIC(_member) READ_ONCE((_memb)->atomic_val)
So that the compiler protects against this mistake.
Jason
