Re: [RFC 1/2] rwsem: introduce upgrade_read interface

[Matthew Wilcox <willy@xxxxxxxxxxxxx>]

On Wed, Oct 16, 2024 at 12:35:59PM +0800, lizhe.67@xxxxxxxxxxxxx wrote:
> +++ b/include/linux/rwsem.h
> @@ -249,6 +249,7 @@ DEFINE_GUARD_COND(rwsem_write, _try, down_write_trylock(_T))
>   * downgrade write lock to read lock
>   */
>  extern void downgrade_write(struct rw_semaphore *sem);
> +extern int upgrade_read(struct rw_semaphore *sem);

This needs __must_check, and I think this should be a bool, not an errno
return.