Re: [patch] spinlocks: remove 'volatile'

Heiko Carstens
2006-07-06T09:28:29Z

> Subject: spinlocks: remove 'volatile'
> From: Ingo Molnar <mingo@elte.hu>
>
> remove 'volatile' from the spinlock types, it causes gcc to
> generate really bad code. (and it's pointless anyway)
>
> this reduces the non-debug SMP kernel's size by 0.2% (!).
>
> Signed-off-by: Ingo Molnar <mingo@elte.hu>
> ---
> include/asm-i386/spinlock_types.h | 4 ++--
> include/asm-x86_64/spinlock_types.h | 4 ++--
> 2 files changed, 4 insertions(+), 4 deletions(-)
>
> Index: linux/include/asm-i386/spinlock_types.h
> ===================================================================
> --- linux.orig/include/asm-i386/spinlock_types.h
> +++ linux/include/asm-i386/spinlock_types.h
> @@ -6,13 +6,13 @@
> #endif
>
> typedef struct {
> - volatile unsigned int slock;
> + unsigned int slock;
> } raw_spinlock_t;
>
> #define __RAW_SPIN_LOCK_UNLOCKED { 1 }
>
> typedef struct {
> - volatile unsigned int lock;
> + unsigned int lock;
> } raw_rwlock_t;

Shouldn't the __raw_read_can_lock and __raw_write_can_lock macros be changed too, just
to make sure the value gets read every single time if it's used in a loop?
Just like the __raw_spin_is_locked already has a (volatile signed char * cast)?