Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756653Ab2KZRDS (ORCPT ); Mon, 26 Nov 2012 12:03:18 -0500 Received: from youngberry.canonical.com ([91.189.89.112]:47277 "EHLO youngberry.canonical.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756573Ab2KZRDO (ORCPT ); Mon, 26 Nov 2012 12:03:14 -0500 From: Herton Ronaldo Krzesinski To: linux-kernel@vger.kernel.org, stable@vger.kernel.org, kernel-team@lists.ubuntu.com Cc: Colin Cross , R Sricharan , Tony Lindgren , Herton Ronaldo Krzesinski Subject: [PATCH 055/270] ARM: OMAP: counter: add locking to read_persistent_clock Date: Mon, 26 Nov 2012 14:55:45 -0200 Message-Id: <1353949160-26803-56-git-send-email-herton.krzesinski@canonical.com> X-Mailer: git-send-email 1.7.9.5 In-Reply-To: <1353949160-26803-1-git-send-email-herton.krzesinski@canonical.com> References: <1353949160-26803-1-git-send-email-herton.krzesinski@canonical.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2221 Lines: 69 3.5.7u1 -stable review patch. If anyone has any objections, please let me know. ------------------ From: Colin Cross commit 9d7d6e363b06934221b81a859d509844c97380df upstream. read_persistent_clock uses a global variable, use a spinlock to ensure non-atomic updates to the variable don't overlap and cause time to move backwards. Signed-off-by: Colin Cross Signed-off-by: R Sricharan Signed-off-by: Tony Lindgren Signed-off-by: Herton Ronaldo Krzesinski --- arch/arm/plat-omap/counter_32k.c | 21 ++++++++++++++------- 1 file changed, 14 insertions(+), 7 deletions(-) diff --git a/arch/arm/plat-omap/counter_32k.c b/arch/arm/plat-omap/counter_32k.c index 2132c4f..721eae5 100644 --- a/arch/arm/plat-omap/counter_32k.c +++ b/arch/arm/plat-omap/counter_32k.c @@ -52,22 +52,29 @@ static u32 notrace omap_32k_read_sched_clock(void) * nsecs and adds to a monotonically increasing timespec. */ static struct timespec persistent_ts; -static cycles_t cycles, last_cycles; +static cycles_t cycles; static unsigned int persistent_mult, persistent_shift; +static DEFINE_SPINLOCK(read_persistent_clock_lock); + static void omap_read_persistent_clock(struct timespec *ts) { unsigned long long nsecs; - cycles_t delta; - struct timespec *tsp = &persistent_ts; + cycles_t last_cycles; + unsigned long flags; + + spin_lock_irqsave(&read_persistent_clock_lock, flags); last_cycles = cycles; cycles = sync32k_cnt_reg ? __raw_readl(sync32k_cnt_reg) : 0; - delta = cycles - last_cycles; - nsecs = clocksource_cyc2ns(delta, persistent_mult, persistent_shift); + nsecs = clocksource_cyc2ns(cycles - last_cycles, + persistent_mult, persistent_shift); + + timespec_add_ns(&persistent_ts, nsecs); + + *ts = persistent_ts; - timespec_add_ns(tsp, nsecs); - *ts = *tsp; + spin_unlock_irqrestore(&read_persistent_clock_lock, flags); } /** -- 1.7.9.5 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/