Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S965847AbdLRXCX (ORCPT ); Mon, 18 Dec 2017 18:02:23 -0500 Received: from mx2.suse.de ([195.135.220.15]:41068 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S965020AbdLRXCR (ORCPT ); Mon, 18 Dec 2017 18:02:17 -0500 From: NeilBrown To: Oleg Drokin , Andreas Dilger , James Simmons , Greg Kroah-Hartman Date: Tue, 19 Dec 2017 10:01:47 +1100 Subject: [PATCH 2/2] staging: lustre: disable preempt while sampling processor id. Cc: lkml , lustre Message-ID: <151363810776.11899.1696679196545013564.stgit@noble> In-Reply-To: <151363798156.11899.768707943431676479.stgit@noble> References: <151363798156.11899.768707943431676479.stgit@noble> User-Agent: StGit/0.17.1-dirty MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1448 Lines: 46 Calling smp_processor_id() without disabling preemption triggers a warning (if CONFIG_DEBUG_PREEMPT). I think the result of cfs_cpt_current() is only used as a hint for load balancing, rather than as a precise and stable indicator of the current CPU. So it doesn't need to be called with preemption disabled. So disable preemption inside cfs_cpt_current() to silence the warning. Signed-off-by: NeilBrown --- .../staging/lustre/lnet/libcfs/linux/linux-cpu.c | 13 +++++++------ 1 file changed, 7 insertions(+), 6 deletions(-) diff --git a/drivers/staging/lustre/lnet/libcfs/linux/linux-cpu.c b/drivers/staging/lustre/lnet/libcfs/linux/linux-cpu.c index d30650f8dcb4..ca8518b8a3e0 100644 --- a/drivers/staging/lustre/lnet/libcfs/linux/linux-cpu.c +++ b/drivers/staging/lustre/lnet/libcfs/linux/linux-cpu.c @@ -517,19 +517,20 @@ EXPORT_SYMBOL(cfs_cpt_spread_node); int cfs_cpt_current(struct cfs_cpt_table *cptab, int remap) { - int cpu = smp_processor_id(); - int cpt = cptab->ctb_cpu2cpt[cpu]; + int cpu; + int cpt; - if (cpt < 0) { - if (!remap) - return cpt; + preempt_disable(); + cpu = smp_processor_id(); + cpt = cptab->ctb_cpu2cpt[cpu]; + if (cpt < 0 && remap) { /* don't return negative value for safety of upper layer, * instead we shadow the unknown cpu to a valid partition ID */ cpt = cpu % cptab->ctb_nparts; } - + preempt_enable(); return cpt; } EXPORT_SYMBOL(cfs_cpt_current);