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Date: Mon, 05 Mar 2012 13:48:15 +0800
From: Alex Shi <alex.shi@...el.com>
To: "tglx@...utronix.de" <tglx@...utronix.de>
Cc: "mingo@...hat.com" <mingo@...hat.com>, hpa@...or.com,
arnd@...db.de, akpm@...ux-foundation.org,
linux-kernel@...r.kernel.org, x86@...nel.org, andi.kleen@...el.com
Subject: Re: [RFC patch] spindep: add cross cache lines checking
On Mon, 2012-03-05 at 13:43 +0800, Alex Shi wrote:
> On Mon, 2012-03-05 at 11:24 +0800, Alex Shi wrote:
> > Oops.
> > Sorry, the patch is not tested well! will update it later.
resent for correct Thomas's e-mail address. Sorry.
>
> corrected version:
> ==========
> >From 28745c1970a61a1420d388660cd9dcc619cd38ba Mon Sep 17 00:00:00 2001
> From: Alex Shi <alex.shi@...el.com>
> Date: Mon, 5 Mar 2012 13:03:35 +0800
> Subject: [PATCH] lockdep: add cross cache lines checking
>
> Modern x86 CPU won't hold whole memory bus when executing 'lock'
> prefixed instructions unless the instruction destination is crossing 2
> cache lines. If so, it is disaster of system performance.
>
> Actually if the lock is not in the 'packed' structure, gcc places it
> safely under x86 arch. But seems add this checking in
> CONFIG_DEBUG_LOCK_ALLOC is harmless.
>
> Inspired-by: Andi Kleen <andi.kleen@...el.com>
> Signed-off-by: Alex Shi <alex.shi@...el.com>
> ---
> arch/x86/include/asm/cache.h | 2 +
> include/asm-generic/cache.h | 2 +
> lib/spinlock_debug.c | 76 ++++++++++++++++++++++-------------------
> 3 files changed, 45 insertions(+), 35 deletions(-)
>
> diff --git a/arch/x86/include/asm/cache.h b/arch/x86/include/asm/cache.h
> index 48f99f1..63c2316 100644
> --- a/arch/x86/include/asm/cache.h
> +++ b/arch/x86/include/asm/cache.h
> @@ -7,6 +7,8 @@
> #define L1_CACHE_SHIFT (CONFIG_X86_L1_CACHE_SHIFT)
> #define L1_CACHE_BYTES (1 << L1_CACHE_SHIFT)
>
> +#define L1_CACHE_SIZE_MASK (~(L1_CACHE_BYTES - 1))
> +
> #define __read_mostly __attribute__((__section__(".data..read_mostly")))
>
> #define INTERNODE_CACHE_SHIFT CONFIG_X86_INTERNODE_CACHE_SHIFT
> diff --git a/include/asm-generic/cache.h b/include/asm-generic/cache.h
> index 1bfcfe5..6f8eb29 100644
> --- a/include/asm-generic/cache.h
> +++ b/include/asm-generic/cache.h
> @@ -9,4 +9,6 @@
> #define L1_CACHE_SHIFT 5
> #define L1_CACHE_BYTES (1 << L1_CACHE_SHIFT)
>
> +#define L1_CACHE_SIZE_MASK (~(L1_CACHE_BYTES - 1))
> +
> #endif /* __ASM_GENERIC_CACHE_H */
> diff --git a/lib/spinlock_debug.c b/lib/spinlock_debug.c
> index 5f3eacd..938a145 100644
> --- a/lib/spinlock_debug.c
> +++ b/lib/spinlock_debug.c
> @@ -13,41 +13,9 @@
> #include <linux/delay.h>
> #include <linux/module.h>
>
> -void __raw_spin_lock_init(raw_spinlock_t *lock, const char *name,
> - struct lock_class_key *key)
> -{
> -#ifdef CONFIG_DEBUG_LOCK_ALLOC
> - /*
> - * Make sure we are not reinitializing a held lock:
> - */
> - debug_check_no_locks_freed((void *)lock, sizeof(*lock));
> - lockdep_init_map(&lock->dep_map, name, key, 0);
> -#endif
> - lock->raw_lock = (arch_spinlock_t)__ARCH_SPIN_LOCK_UNLOCKED;
> - lock->magic = SPINLOCK_MAGIC;
> - lock->owner = SPINLOCK_OWNER_INIT;
> - lock->owner_cpu = -1;
> -}
> -
> -EXPORT_SYMBOL(__raw_spin_lock_init);
> -
> -void __rwlock_init(rwlock_t *lock, const char *name,
> - struct lock_class_key *key)
> -{
> -#ifdef CONFIG_DEBUG_LOCK_ALLOC
> - /*
> - * Make sure we are not reinitializing a held lock:
> - */
> - debug_check_no_locks_freed((void *)lock, sizeof(*lock));
> - lockdep_init_map(&lock->dep_map, name, key, 0);
> -#endif
> - lock->raw_lock = (arch_rwlock_t) __ARCH_RW_LOCK_UNLOCKED;
> - lock->magic = RWLOCK_MAGIC;
> - lock->owner = SPINLOCK_OWNER_INIT;
> - lock->owner_cpu = -1;
> -}
> -
> -EXPORT_SYMBOL(__rwlock_init);
> +#define is_cross_lines(p) \
> + (((unsigned long)(p) & L1_CACHE_SIZE_MASK) != \
> + (((unsigned long)(p) + sizeof(*p) - 1) & L1_CACHE_SIZE_MASK)) \
>
> static void spin_dump(raw_spinlock_t *lock, const char *msg)
> {
> @@ -296,3 +264,41 @@ void do_raw_write_unlock(rwlock_t *lock)
> debug_write_unlock(lock);
> arch_write_unlock(&lock->raw_lock);
> }
> +
> +void __raw_spin_lock_init(raw_spinlock_t *lock, const char *name,
> + struct lock_class_key *key)
> +{
> +#ifdef CONFIG_DEBUG_LOCK_ALLOC
> + /*
> + * Make sure we are not reinitializing a held lock:
> + */
> + debug_check_no_locks_freed((void *)lock, sizeof(*lock));
> + lockdep_init_map(&lock->dep_map, name, key, 0);
> + SPIN_BUG_ON(is_cross_lines(&lock->raw_lock), lock,
> + "!!! the lock cross cache lines !!!");
> +#endif
> + lock->raw_lock = (arch_spinlock_t)__ARCH_SPIN_LOCK_UNLOCKED;
> + lock->magic = SPINLOCK_MAGIC;
> + lock->owner = SPINLOCK_OWNER_INIT;
> + lock->owner_cpu = -1;
> +}
> +EXPORT_SYMBOL(__raw_spin_lock_init);
> +
> +void __rwlock_init(rwlock_t *lock, const char *name,
> + struct lock_class_key *key)
> +{
> +#ifdef CONFIG_DEBUG_LOCK_ALLOC
> + /*
> + * Make sure we are not reinitializing a held lock:
> + */
> + debug_check_no_locks_freed((void *)lock, sizeof(*lock));
> + lockdep_init_map(&lock->dep_map, name, key, 0);
> + RWLOCK_BUG_ON(is_cross_lines(&lock->raw_lock), lock,
> + "!!! the lock cross cache lines !!!");
> +#endif
> + lock->raw_lock = (arch_rwlock_t) __ARCH_RW_LOCK_UNLOCKED;
> + lock->magic = RWLOCK_MAGIC;
> + lock->owner = SPINLOCK_OWNER_INIT;
> + lock->owner_cpu = -1;
> +}
> +EXPORT_SYMBOL(__rwlock_init);
--
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