Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756450Ab1DLIEz (ORCPT ); Tue, 12 Apr 2011 04:04:55 -0400 Received: from mga01.intel.com ([192.55.52.88]:8881 "EHLO mga01.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753508Ab1DLIEG (ORCPT ); Tue, 12 Apr 2011 04:04:06 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.64,194,1301900400"; d="scan'208";a="908410307" Subject: [PATCH 3/4]percpu_counter: fix code for 32bit systems From: Shaohua Li To: lkml Cc: Andrew Morton , cl@linux.com, tj@kernel.org Content-Type: text/plain; charset="UTF-8" Date: Tue, 12 Apr 2011 16:04:04 +0800 Message-ID: <1302595444.3981.129.camel@sli10-conroe> Mime-Version: 1.0 X-Mailer: Evolution 2.30.3 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2697 Lines: 100 percpu_counter.counter is a 's64'. Accessing it in 32-bit system is racing. we need some locking to protect it otherwise some very wrong value could be accessed. Signed-off-by: Shaohua Li --- include/linux/percpu_counter.h | 43 +++++++++++++++++++++++++++++++---------- 1 file changed, 33 insertions(+), 10 deletions(-) Index: linux/include/linux/percpu_counter.h =================================================================== --- linux.orig/include/linux/percpu_counter.h 2011-04-12 15:48:44.000000000 +0800 +++ linux/include/linux/percpu_counter.h 2011-04-12 15:48:54.000000000 +0800 @@ -54,7 +54,15 @@ static inline s64 percpu_counter_sum(str static inline s64 percpu_counter_read(struct percpu_counter *fbc) { +#if BITS_PER_LONG == 32 + s64 count; + spin_lock(&fbc->lock); + count = fbc->count; + spin_unlock(&fbc->lock); + return count; +#else return fbc->count; +#endif } static inline int percpu_counter_initialized(struct percpu_counter *fbc) @@ -68,9 +76,20 @@ struct percpu_counter { s64 count; }; -static inline int percpu_counter_init(struct percpu_counter *fbc, s64 amount) +static inline void percpu_counter_set(struct percpu_counter *fbc, s64 amount) { +#if BITS_PER_LONG == 32 + preempt_disable(); fbc->count = amount; + preempt_enable(); +#else + fbc->count = amount; +#endif +} + +static inline int percpu_counter_init(struct percpu_counter *fbc, s64 amount) +{ + percpu_counter_set(fbc, amount); return 0; } @@ -78,16 +97,25 @@ static inline void percpu_counter_destro { } -static inline void percpu_counter_set(struct percpu_counter *fbc, s64 amount) +static inline s64 percpu_counter_read(struct percpu_counter *fbc) { - fbc->count = amount; +#if BITS_PER_LONG == 32 + s64 count; + preempt_disable(); + count = fbc->count; + preempt_enable(); + return count; +#else + return fbc->count; +#endif } static inline int percpu_counter_compare(struct percpu_counter *fbc, s64 rhs) { - if (fbc->count > rhs) + s64 count = percpu_counter_read(fbc); + if (count > rhs) return 1; - else if (fbc->count < rhs) + else if (count < rhs) return -1; else return 0; @@ -107,11 +135,6 @@ __percpu_counter_add(struct percpu_count percpu_counter_add(fbc, amount); } -static inline s64 percpu_counter_read(struct percpu_counter *fbc) -{ - return fbc->count; -} - static inline s64 percpu_counter_sum(struct percpu_counter *fbc) { return percpu_counter_read(fbc); -- 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/