From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751168AbVHLNK3 (ORCPT ); Fri, 12 Aug 2005 09:10:29 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751170AbVHLNK2 (ORCPT ); Fri, 12 Aug 2005 09:10:28 -0400 Received: from e31.co.us.ibm.com ([32.97.110.129]:60821 "EHLO e31.co.us.ibm.com") by vger.kernel.org with ESMTP id S1751168AbVHLNK2 (ORCPT ); Fri, 12 Aug 2005 09:10:28 -0400 Subject: [-mm patch] Avoid divide by zero errors in sched.c From: Dave Kleikamp To: Andrew Morton Cc: linux-kernel , Con Kolivas Content-Type: text/plain Date: Fri, 12 Aug 2005 08:10:22 -0500 Message-Id: <1123852222.9234.7.camel@kleikamp.austin.ibm.com> Mime-Version: 1.0 X-Mailer: Evolution 2.2.3 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org This patch fixes a divide-by-zero error that I hit on a two-way i386 machine. rq->nr_running is tested to be non-zero, but may change by the time it is used in the division. Saving the value to a local variable ensures that the same value that is checked is used in the division. Signed-off-by: Dave Kleikamp Cc: Con Kolivas diff -urp linux-2.6.13-rc5-mm1/kernel/sched.c linux/kernel/sched.c --- linux-2.6.13-rc5-mm1/kernel/sched.c 2005-08-11 09:41:30.000000000 -0500 +++ linux/kernel/sched.c 2005-08-11 09:47:27.000000000 -0500 @@ -989,15 +989,16 @@ void kick_process(task_t *p) static inline unsigned long __source_load(int cpu, int type, enum idle_type idle) { runqueue_t *rq = cpu_rq(cpu); + unsigned long running = rq->nr_running; unsigned long source_load, cpu_load = rq->cpu_load[type-1], - load_now = rq->nr_running * SCHED_LOAD_SCALE; + load_now = running * SCHED_LOAD_SCALE; if (type == 0) source_load = load_now; else source_load = min(cpu_load, load_now); - if (rq->nr_running > 1 || (idle == NOT_IDLE && rq->nr_running)) + if (running > 1 || (idle == NOT_IDLE && running)) /* * If we are busy rebalancing the load is biased by * priority to create 'nice' support across cpus. When @@ -1006,7 +1007,7 @@ static inline unsigned long __source_loa * prevent idle rebalance from trying to pull tasks from a * queue with only one running task. */ - source_load = source_load * rq->prio_bias / rq->nr_running; + source_load = source_load * rq->prio_bias / running; return source_load; } @@ -1022,16 +1023,17 @@ static inline unsigned long source_load( static inline unsigned long __target_load(int cpu, int type, enum idle_type idle) { runqueue_t *rq = cpu_rq(cpu); + unsigned long running = rq->nr_running; unsigned long target_load, cpu_load = rq->cpu_load[type-1], - load_now = rq->nr_running * SCHED_LOAD_SCALE; + load_now = running * SCHED_LOAD_SCALE; if (type == 0) target_load = load_now; else target_load = max(cpu_load, load_now); - if (rq->nr_running > 1 || (idle == NOT_IDLE && rq->nr_running)) - target_load = target_load * rq->prio_bias / rq->nr_running; + if (running > 1 || (idle == NOT_IDLE && running)) + target_load = target_load * rq->prio_bias / running; return target_load; } -- David Kleikamp IBM Linux Technology Center