Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S964995AbWH2Oqg (ORCPT ); Tue, 29 Aug 2006 10:46:36 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S965002AbWH2Oqg (ORCPT ); Tue, 29 Aug 2006 10:46:36 -0400 Received: from mailhub.sw.ru ([195.214.233.200]:12052 "EHLO relay.sw.ru") by vger.kernel.org with ESMTP id S964995AbWH2Oqf (ORCPT ); Tue, 29 Aug 2006 10:46:35 -0400 Message-ID: <44F4540C.8050205@sw.ru> Date: Tue, 29 Aug 2006 18:49:48 +0400 From: Kirill Korotaev User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.7.13) Gecko/20060417 X-Accept-Language: en-us, en, ru MIME-Version: 1.0 To: Andrew Morton CC: Linux Kernel Mailing List , Alan Cox , Christoph Hellwig , Pavel Emelianov , Andrey Savochkin , devel@openvz.org, Rik van Riel , Andi Kleen , Oleg Nesterov , Alexey Dobriyan , Matt Helsley , CKRM-Tech Subject: [PATCH 1/7] introduce atomic_dec_and_lock_irqsave() References: <44F45045.70402@sw.ru> In-Reply-To: <44F45045.70402@sw.ru> Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2849 Lines: 88 Oleg Nesterov noticed to me that the construction like (used in beancounter patches and free_uid()): local_irq_save(flags); if (atomic_dec_and_lock(&refcnt, &lock)) ... is not that good for preemtible kernels, since with preemption spin_lock() can schedule() to reduce latency. However, it won't schedule if interrupts are disabled. So this patch introduces atomic_dec_and_lock_irqsave() as a logical counterpart to atomic_dec_and_lock(). Signed-Off-By: Pavel Emelianov Signed-Off-By: Kirill Korotaev --- include/linux/spinlock.h | 6 ++++++ kernel/user.c | 5 +---- lib/dec_and_lock.c | 19 +++++++++++++++++++ 3 files changed, 26 insertions(+), 4 deletions(-) --- ./include/linux/spinlock.h.dlirq 2006-08-28 10:17:35.000000000 +0400 +++ ./include/linux/spinlock.h 2006-08-28 11:22:37.000000000 +0400 @@ -266,6 +266,12 @@ extern int _atomic_dec_and_lock(atomic_t #define atomic_dec_and_lock(atomic, lock) \ __cond_lock(lock, _atomic_dec_and_lock(atomic, lock)) +extern int _atomic_dec_and_lock_irqsave(atomic_t *atomic, spinlock_t *lock, + unsigned long *flagsp); +#define atomic_dec_and_lock_irqsave(atomic, lock, flags) \ + __cond_lock(lock, \ + _atomic_dec_and_lock_irqsave(atomic, lock, &flags)) + /** * spin_can_lock - would spin_trylock() succeed? * @lock: the spinlock in question. --- ./kernel/user.c.dlirq 2006-07-10 12:39:20.000000000 +0400 +++ ./kernel/user.c 2006-08-28 11:08:56.000000000 +0400 @@ -108,15 +108,12 @@ void free_uid(struct user_struct *up) if (!up) return; - local_irq_save(flags); - if (atomic_dec_and_lock(&up->__count, &uidhash_lock)) { + if (atomic_dec_and_lock_irqsave(&up->__count, &uidhash_lock, flags)) { uid_hash_remove(up); spin_unlock_irqrestore(&uidhash_lock, flags); key_put(up->uid_keyring); key_put(up->session_keyring); kmem_cache_free(uid_cachep, up); - } else { - local_irq_restore(flags); } } --- ./lib/dec_and_lock.c.dlirq 2006-04-21 11:59:36.000000000 +0400 +++ ./lib/dec_and_lock.c 2006-08-28 11:22:08.000000000 +0400 @@ -33,3 +33,22 @@ int _atomic_dec_and_lock(atomic_t *atomi } EXPORT_SYMBOL(_atomic_dec_and_lock); + +/* + * the same, but takes the lock with _irqsave + */ +int _atomic_dec_and_lock_irqsave(atomic_t *atomic, spinlock_t *lock, + unsigned long *flagsp) +{ +#ifdef CONFIG_SMP + if (atomic_add_unless(atomic, -1, 1)) + return 0; +#endif + spin_lock_irqsave(lock, *flagsp); + if (atomic_dec_and_test(atomic)) + return 1; + spin_unlock_irqrestore(lock, *flagsp); + return 0; +} + +EXPORT_SYMBOL(_atomic_dec_and_lock_irqsave); - 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/