From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752511AbcGMNBX (ORCPT ); Wed, 13 Jul 2016 09:01:23 -0400 Received: from mail-wm0-f65.google.com ([74.125.82.65]:35283 "EHLO mail-wm0-f65.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752384AbcGMNBS (ORCPT ); Wed, 13 Jul 2016 09:01:18 -0400 From: Nicolai Stange To: Thomas Gleixner Cc: John Stultz , linux-kernel@vger.kernel.org, Nicolai Stange Subject: [RFC v3 2/3] kernel/time/clockevents: make setting of ->mult and ->mult_mono atomic Date: Wed, 13 Jul 2016 15:00:16 +0200 Message-Id: <20160713130017.8202-3-nicstange@gmail.com> X-Mailer: git-send-email 2.9.0 In-Reply-To: <20160713130017.8202-1-nicstange@gmail.com> References: <20160713130017.8202-1-nicstange@gmail.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org In order to avoid races between setting a struct clock_event_device's ->mult_mono in clockevents_update_freq() and yet to be implemented updates triggered from the timekeeping core, the setting of ->mult and ->mult_mono should be made atomic. Protect the update in clockevents_update_freq() by locking the clockevents_lock spinlock. Frequency updates are expected to be done seldomly and thus, taking this subsystem lock should not have any impact on performance. Use a raw_spin_lock_irq_save()/raw_spin_unlock_irq_restore() pair for locking/unlocking the clockevents_lock spinlock. Purge the now redundant local_irq_save()/local_irq_restore() pair from clockevents_update_freq(). Since the call to tick_broadcast_update_freq() isn't done with interrupts disabled anymore, its raw_spin_lock()/raw_spin_unlock() pair must be converted to raw_spin_lock_irq_save()/raw_spin_unlock_irq_restore(). Signed-off-by: Nicolai Stange --- kernel/time/clockevents.c | 7 ++++--- kernel/time/tick-broadcast.c | 5 +++-- 2 files changed, 7 insertions(+), 5 deletions(-) diff --git a/kernel/time/clockevents.c b/kernel/time/clockevents.c index ba7fea4..ec01375 100644 --- a/kernel/time/clockevents.c +++ b/kernel/time/clockevents.c @@ -589,11 +589,12 @@ int clockevents_update_freq(struct clock_event_device *dev, u32 freq) unsigned long flags; int ret; - local_irq_save(flags); ret = tick_broadcast_update_freq(dev, freq); - if (ret == -ENODEV) + if (ret == -ENODEV) { + raw_spin_lock_irqsave(&clockevents_lock, flags); ret = __clockevents_update_freq(dev, freq); - local_irq_restore(flags); + raw_spin_unlock_irqrestore(&clockevents_lock, flags); + } return ret; } diff --git a/kernel/time/tick-broadcast.c b/kernel/time/tick-broadcast.c index f6aae79..9c94c41 100644 --- a/kernel/time/tick-broadcast.c +++ b/kernel/time/tick-broadcast.c @@ -125,11 +125,12 @@ int tick_is_broadcast_device(struct clock_event_device *dev) int tick_broadcast_update_freq(struct clock_event_device *dev, u32 freq) { int ret = -ENODEV; + unsigned long flags; if (tick_is_broadcast_device(dev)) { - raw_spin_lock(&tick_broadcast_lock); + raw_spin_lock_irqsave(&tick_broadcast_lock, flags); ret = __clockevents_update_freq(dev, freq); - raw_spin_unlock(&tick_broadcast_lock); + raw_spin_unlock_irqrestore(&tick_broadcast_lock, flags); } return ret; } -- 2.9.0