From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.linuxfoundation.org ([140.211.169.12]:40945 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933538AbcILPbP (ORCPT ); Mon, 12 Sep 2016 11:31:15 -0400 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Steven Rostedt , Peter Zijlstra , John Stultz , Thomas Gleixner Subject: [PATCH 4.7 28/59] timekeeping: Avoid taking lock in NMI path with CONFIG_DEBUG_TIMEKEEPING Date: Mon, 12 Sep 2016 17:29:48 +0200 Message-Id: <20160912152129.951232351@linuxfoundation.org> In-Reply-To: <20160912152128.765864031@linuxfoundation.org> References: <20160912152128.765864031@linuxfoundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: stable-owner@vger.kernel.org List-ID: 4.7-stable review patch. If anyone has any objections, please let me know. ------------------ From: John Stultz commit 27727df240c7cc84f2ba6047c6f18d5addfd25ef upstream. When I added some extra sanity checking in timekeeping_get_ns() under CONFIG_DEBUG_TIMEKEEPING, I missed that the NMI safe __ktime_get_fast_ns() method was using timekeeping_get_ns(). Thus the locking added to the debug checks broke the NMI-safety of __ktime_get_fast_ns(). This patch open-codes the timekeeping_get_ns() logic for __ktime_get_fast_ns(), so can avoid any deadlocks in NMI. Fixes: 4ca22c2648f9 "timekeeping: Add warnings when overflows or underflows are observed" Reported-by: Steven Rostedt Reported-by: Peter Zijlstra Signed-off-by: John Stultz Link: http://lkml.kernel.org/r/1471993702-29148-2-git-send-email-john.stultz@linaro.org Signed-off-by: Thomas Gleixner Signed-off-by: Greg Kroah-Hartman --- kernel/time/timekeeping.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) --- a/kernel/time/timekeeping.c +++ b/kernel/time/timekeeping.c @@ -401,7 +401,10 @@ static __always_inline u64 __ktime_get_f do { seq = raw_read_seqcount_latch(&tkf->seq); tkr = tkf->base + (seq & 0x01); - now = ktime_to_ns(tkr->base) + timekeeping_get_ns(tkr); + now = ktime_to_ns(tkr->base); + + now += clocksource_delta(tkr->read(tkr->clock), + tkr->cycle_last, tkr->mask); } while (read_seqcount_retry(&tkf->seq, seq)); return now;