From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S965775AbcCJLIj (ORCPT ); Thu, 10 Mar 2016 06:08:39 -0500 Received: from torg.zytor.com ([198.137.202.12]:38436 "EHLO terminus.zytor.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S965543AbcCJLI3 (ORCPT ); Thu, 10 Mar 2016 06:08:29 -0500 Date: Thu, 10 Mar 2016 03:07:24 -0800 From: tip-bot for Borislav Petkov Message-ID: Cc: linux-kernel@vger.kernel.org, luto@amacapital.net, luto@kernel.org, hpa@zytor.com, torvalds@linux-foundation.org, mingo@kernel.org, bp@alien8.de, bp@suse.de, ray.huang@amd.com, peterz@infradead.org, tglx@linutronix.de, a.p.zijlstra@chello.nl Reply-To: bp@alien8.de, linux-kernel@vger.kernel.org, hpa@zytor.com, luto@amacapital.net, luto@kernel.org, torvalds@linux-foundation.org, mingo@kernel.org, ray.huang@amd.com, peterz@infradead.org, a.p.zijlstra@chello.nl, tglx@linutronix.de, bp@suse.de In-Reply-To: <20160309205622.GG6564@pd.tnic> References: <20160309205622.GG6564@pd.tnic> To: linux-tip-commits@vger.kernel.org Subject: [tip:x86/urgent] x86/delay: Avoid preemptible context checks in delay_mwaitx() Git-Commit-ID: 84477336ec03f8061ffd6908da341e063e5d6d1f X-Mailer: tip-git-log-daemon Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Content-Type: text/plain; charset=UTF-8 Content-Disposition: inline Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Commit-ID: 84477336ec03f8061ffd6908da341e063e5d6d1f Gitweb: http://git.kernel.org/tip/84477336ec03f8061ffd6908da341e063e5d6d1f Author: Borislav Petkov AuthorDate: Wed, 9 Mar 2016 21:56:22 +0100 Committer: Ingo Molnar CommitDate: Thu, 10 Mar 2016 11:27:12 +0100 x86/delay: Avoid preemptible context checks in delay_mwaitx() We do use this_cpu_ptr(&cpu_tss) as a cacheline-aligned, seldomly accessed per-cpu var as the MONITORX target in delay_mwaitx(). However, when called in preemptible context, this_cpu_ptr -> smp_processor_id() -> debug_smp_processor_id() fires: BUG: using smp_processor_id() in preemptible [00000000] code: udevd/312 caller is delay_mwaitx+0x40/0xa0 But we don't care about that check - we only need cpu_tss as a MONITORX target and it doesn't really matter which CPU's var we're touching as we're going idle anyway. Fix that. Suggested-by: Andy Lutomirski Signed-off-by: Borislav Petkov Cc: Andy Lutomirski Cc: Huang Rui Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: spg_linux_kernel@amd.com Link: http://lkml.kernel.org/r/20160309205622.GG6564@pd.tnic Signed-off-by: Ingo Molnar --- arch/x86/lib/delay.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/arch/x86/lib/delay.c b/arch/x86/lib/delay.c index e912b2f..2f07c29 100644 --- a/arch/x86/lib/delay.c +++ b/arch/x86/lib/delay.c @@ -102,7 +102,7 @@ static void delay_mwaitx(unsigned long __loops) * Use cpu_tss as a cacheline-aligned, seldomly * accessed per-cpu variable as the monitor target. */ - __monitorx(this_cpu_ptr(&cpu_tss), 0, 0); + __monitorx(raw_cpu_ptr(&cpu_tss), 0, 0); /* * AMD, like Intel, supports the EAX hint and EAX=0xf