Messages in this thread Patch in this message | | | Date | Thu, 20 Oct 2005 23:50:47 +0200 | From | Ingo Molnar <> | Subject | Re: [PATCH] i386 spinlocks should use the full 32 bits, not only 8 bits |
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* Arjan van de Ven <arjan@infradead.org> wrote:
> > Is that intentional though? With <randon .config> my mm/swapfile.i has an > > unreferenced > > > > static inline void __raw_spin_unlock(raw_spinlock_t *lock) > > { > > __asm__ __volatile__( > > "movb $1,%0" :"=m" (lock->slock) : : "memory" > > ); > > } > > > > which either a) shouldn't be there or b) should be referenced. > > > > Ingo, can you confirm that x86's spin_unlock is never inlined? If so, > > what's my __raw_spin_unlock() doing there?
__raw_spin_unlock is currently only inlined in the kernel/spinlock.c code.
> I would really want this one inlined! A movb is a much shorter code > sequence than a call (esp if you factor in argument setup). > De-inlining to save space is nice and all, but it can go too far....
yeah, it makes sense to inline the single-instruction unlock operations: nondebug spin_unlock(), read_unlock() and write_unlock(). This gives a 0.2% code-size reduction:
text data bss dec hex filename 4072031 858208 387196 5317435 51233b vmlinux-smp-uninlined 4060671 858212 387196 5306079 50f6df vmlinux-smp-inlined
patch against -rc5. Boot-tested on a 4-way x86 SMP box.
Ingo
Signed-off-by: Ingo Molnar <mingo@elte.hu>
include/linux/spinlock.h | 15 ++++++++++++--- 1 files changed, 12 insertions(+), 3 deletions(-)
Index: linux/include/linux/spinlock.h =================================================================== --- linux.orig/include/linux/spinlock.h +++ linux/include/linux/spinlock.h @@ -171,9 +171,18 @@ extern int __lockfunc generic__raw_read_ #define write_lock_irq(lock) _write_lock_irq(lock) #define write_lock_bh(lock) _write_lock_bh(lock) -#define spin_unlock(lock) _spin_unlock(lock) -#define write_unlock(lock) _write_unlock(lock) -#define read_unlock(lock) _read_unlock(lock) +/* + * We inline the unlock functions in the nondebug case: + */ +#ifdef CONFIG_DEBUG_SPINLOCK +# define spin_unlock(lock) _spin_unlock(lock) +# define read_unlock(lock) _read_unlock(lock) +# define write_unlock(lock) _write_unlock(lock) +#else +# define spin_unlock(lock) __raw_spin_unlock(&(lock)->raw_lock) +# define read_unlock(lock) __raw_read_unlock(&(lock)->raw_lock) +# define write_unlock(lock) __raw_write_unlock(&(lock)->raw_lock) +#endif #define spin_unlock_irqrestore(lock, flags) \ _spin_unlock_irqrestore(lock, flags) - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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