Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755085Ab1EKPqu (ORCPT ); Wed, 11 May 2011 11:46:50 -0400 Received: from mga02.intel.com ([134.134.136.20]:8648 "EHLO mga02.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754751Ab1EKPqX (ORCPT ); Wed, 11 May 2011 11:46:23 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.64,351,1301900400"; d="scan'208";a="641126610" Message-Id: <20110511081433.482521472@sli10-conroe.sh.intel.com> User-Agent: quilt/0.48-1 Date: Wed, 11 May 2011 16:10:13 +0800 From: Shaohua Li To: linux-kernel@vger.kernel.org Cc: akpm@linux-foundation.org, tj@kernel.org, eric.dumazet@gmail.com, cl@linux.com, npiggin@kernel.dk, Shaohua Li Subject: [patch v2 1/5] percpu_counter: fix code for 32bit systems for UP References: <20110511081012.903869567@sli10-conroe.sh.intel.com> Content-Disposition: inline; filename=percpu-counter-32bits.patch Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2160 Lines: 76 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 | 31 +++++++++++++++++++++++-------- 1 file changed, 23 insertions(+), 8 deletions(-) Index: linux/include/linux/percpu_counter.h =================================================================== --- linux.orig/include/linux/percpu_counter.h 2011-05-05 10:33:12.000000000 +0800 +++ linux/include/linux/percpu_counter.h 2011-05-06 11:19:26.000000000 +0800 @@ -101,14 +101,34 @@ static inline void percpu_counter_destro 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 s64 percpu_counter_read(struct percpu_counter *fbc) +{ +#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; @@ -128,18 +148,13 @@ __percpu_counter_add(struct percpu_count percpu_counter_add(fbc, amount); } -static inline s64 percpu_counter_read(struct percpu_counter *fbc) -{ - return fbc->count; -} - /* * percpu_counter is intended to track positive number. In UP case, the number * should never be negative. */ static inline s64 percpu_counter_read_positive(struct percpu_counter *fbc) { - return fbc->count; + return percpu_counter_read(fbc); } static inline s64 percpu_counter_sum_positive(struct percpu_counter *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/