Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753956AbcKSQMV (ORCPT ); Sat, 19 Nov 2016 11:12:21 -0500 Received: from mail-wm0-f65.google.com ([74.125.82.65]:35441 "EHLO mail-wm0-f65.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753905AbcKSQMQ (ORCPT ); Sat, 19 Nov 2016 11:12:16 -0500 From: Nicolai Stange To: Thomas Gleixner Cc: John Stultz , linux-kernel@vger.kernel.org, Nicolai Stange Subject: [RFC v8 24/28] clockevents: make setting of ->mult and ->mult_adjusted atomic Date: Sat, 19 Nov 2016 17:10:32 +0100 Message-Id: <20161119161036.12679-13-nicstange@gmail.com> X-Mailer: git-send-email 2.10.2 In-Reply-To: <20161119160055.12491-1-nicstange@gmail.com> References: <20161119160055.12491-1-nicstange@gmail.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1617 Lines: 44 In order to avoid races between setting a struct clock_event_device's ->mult_adjusted in clockevents_update_freq() and yet to be implemented updates triggered from the timekeeping core, the setting of ->mult and ->mult_adjusted 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. Note that the call to tick_broadcast_update_freq() is also protected by this clockevents_lock and thus, this patch can take the tick_broadcast_lock with the clockevents_lock being held. However, this is supposed to be safe since the sequence __clockevents_unbind() -> clockevents_replace() -> tick_install_replacement() -> tick_setup_device() -> tick_device_uses_broadcast() already does this, too. Signed-off-by: Nicolai Stange --- kernel/time/clockevents.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/kernel/time/clockevents.c b/kernel/time/clockevents.c index d9a53af..7dd71bb 100644 --- a/kernel/time/clockevents.c +++ b/kernel/time/clockevents.c @@ -658,11 +658,11 @@ int clockevents_update_freq(struct clock_event_device *dev, u32 freq) unsigned long flags; int ret; - local_irq_save(flags); + raw_spin_lock_irqsave(&clockevents_lock, flags); ret = tick_broadcast_update_freq(dev, freq); if (ret == -ENODEV) ret = __clockevents_update_freq(dev, freq); - local_irq_restore(flags); + raw_spin_unlock_irqrestore(&clockevents_lock, flags); return ret; } -- 2.10.2