On Mon, Mar 25, 2019 at 01:57:57PM +0100, Arnd Bergmann wrote:
> When lockdep is enabled, and -Wuninitialized warnings are enabled,
> clang produces a silly warning for every file we compile:
>
> In file included from kernel/sched/fair.c:23:
> kernel/sched/sched.h:1094:15: error: variable 'cookie' is uninitialized when
> used here [-Werror,-Wuninitialized]
> rf->cookie = lockdep_pin_lock(&rq->lock);
> ^~~~~~~~~~~~~~~~~~~~~~~~~~~
> include/linux/lockdep.h:474:60: note: expanded from macro 'lockdep_pin_lock'
> #define lockdep_pin_lock(l) ({ struct pin_cookie cookie;
> cookie; })
>
> ^~~~~~
> kernel/sched/sched.h:1094:15: note: variable 'cookie' is declared here
> include/linux/lockdep.h:474:34: note: expanded from macro 'lockdep_pin_lock'
> #define lockdep_pin_lock(l) ({ struct pin_cookie cookie;
> cookie; })
> ^
> As the 'struct pin_cookie' structure is empty in this configuration,
> there is no need to initialize it for correctness, but it also
> does not hurt to set it to an empty structure, so do that to
> avoid the warning.
>
> Signed-off-by: Arnd Bergmann <[email protected]>
> ---
> include/linux/lockdep.h | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/include/linux/lockdep.h b/include/linux/lockdep.h
> index 79c3873d58ac..31d7549933eb 100644
> --- a/include/linux/lockdep.h
> +++ b/include/linux/lockdep.h
> @@ -471,7 +471,7 @@ struct pin_cookie { };
>
> #define NIL_COOKIE (struct pin_cookie){ }
>
> -#define lockdep_pin_lock(l) ({ struct pin_cookie cookie;
> cookie; })
> +#define lockdep_pin_lock(l) ({ struct pin_cookie cookie =
> {}; cookie; })
> #define lockdep_repin_lock(l, c) do { (void)(l); (void)(c); }
> while (0)
> #define lockdep_unpin_lock(l, c) do { (void)(l); (void)(c); }
> while (0)
Acked-by: Will Deacon <[email protected]>
Will
