From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1422763Ab3CVRuH (ORCPT ); Fri, 22 Mar 2013 13:50:07 -0400 Received: from ams-iport-1.cisco.com ([144.254.224.140]:12275 "EHLO ams-iport-1.cisco.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1422717Ab3CVRuE (ORCPT ); Fri, 22 Mar 2013 13:50:04 -0400 X-Greylist: delayed 586 seconds by postgrey-1.27 at vger.kernel.org; Fri, 22 Mar 2013 13:50:04 EDT X-IronPort-AV: E=Sophos;i="4.84,893,1355097600"; d="scan'208";a="152091224" From: Henrik Austad To: Chris Metcalf Cc: LKML , Henrik Austad Subject: [PATCH] tile: ns2cycles must be called with preempt disabled. Date: Fri, 22 Mar 2013 18:37:51 +0100 Message-Id: <1363973871-13199-1-git-send-email-haustad@cisco.com> X-Mailer: git-send-email 1.7.10.1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org ns2cycles use per_cpu variables, and will, eventually, find its way into smp_processord_id(). The latter must be called with either preempt disabled, irq's off, from a thread locked to a single core or early in the bootprocess (according to debug_smp_processor_id()) BUG: using smp_processor_id() in preemptible [00000000] code: systemd-modules/367 caller is ns2cycles+0x40/0xb8 Starting stack dump of tid 367, pid 367 (systemd-modules) on cpu 2 at cycle 20969956421 frame 0: 0xfffffff70004b860 dump_stack+0x0/0x20 (sp 0xfffffe407993fa90) frame 1: 0xfffffff7006abc28 debug_smp_processor_id+0x1a8/0x1e0 (sp 0xfffffe407993fa90) frame 2: 0xfffffff7004d7b40 ns2cycles+0x40/0xb8 (sp 0xfffffe407993fab8) frame 3: 0xfffffff7004dc578 __ndelay+0x38/0x80 (sp 0xfffffe407993fae0) Note: wrapping the -entire- delay-loop in a preempt-off section can be a bad idea as long delays would case kernel lockups without being able to preempt the thread at all. Signed-off-by: Henrik Austad --- arch/tile/lib/delay.c | 2 ++ 1 files changed, 2 insertions(+), 0 deletions(-) diff --git a/arch/tile/lib/delay.c b/arch/tile/lib/delay.c index cdacdd1..a53cdcd 100644 --- a/arch/tile/lib/delay.c +++ b/arch/tile/lib/delay.c @@ -30,7 +30,9 @@ EXPORT_SYMBOL(__udelay); void __ndelay(unsigned long nsecs) { cycles_t target = get_cycles(); + preempt_disable(); target += ns2cycles(nsecs); + preempt_enable(); while (get_cycles() < target) cpu_relax(); } -- 1.7.2.5