From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753247AbbDGCLX (ORCPT ); Mon, 6 Apr 2015 22:11:23 -0400 Received: from mail-pd0-f181.google.com ([209.85.192.181]:36478 "EHLO mail-pd0-f181.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753129AbbDGCLN (ORCPT ); Mon, 6 Apr 2015 22:11:13 -0400 From: Viresh Kumar To: Thomas Gleixner , Ingo Molnar , Peter Zijlstra Cc: linaro-kernel@lists.linaro.org, linux-kernel@vger.kernel.org, Preeti U Murthy , Viresh Kumar Subject: [PATCH V2 1/2] hrtimer: update '->active_bases' before calling hrtimer_force_reprogram() Date: Tue, 7 Apr 2015 07:40:52 +0530 Message-Id: X-Mailer: git-send-email 2.3.0.rc0.44.ga94655d In-Reply-To: References: In-Reply-To: References: Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 'active_bases' indicates which clock-base have active timers. While it is updated correctly, it is hardly used. Next commit will start using it to make code more efficient, but before that we need to fix a problem. While removing hrtimers, in __remove_hrtimer(): - We first remove the hrtimer from the queue. - Then reprogram clockevent device if required (hrtimer_force_reprogram()). - And then finally clear 'active_bases', if no more timers are pending on the current clock base (from which we are removing the hrtimer). hrtimer_force_reprogram() needs to loop over all active clock bases to find the next expiry event, and while doing so it will use 'active_bases' (after next commit). And it will find the current base active, as we haven't cleared it until now, even if current clock base has no more hrtimers queued. The next commit will skip validating what timerqueue_getnext() returns, as that is guaranteed to be valid for an active base, and the above stated problem will result in a crash then (Because timerqueue_getnext() will return NULL for the current clock base). So, fix this issue by clearing active_bases before calling hrtimer_force_reprogram(). Reviewed-by: Preeti U Murthy Signed-off-by: Viresh Kumar --- kernel/time/hrtimer.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/kernel/time/hrtimer.c b/kernel/time/hrtimer.c index bee0c1f78091..3152f327c988 100644 --- a/kernel/time/hrtimer.c +++ b/kernel/time/hrtimer.c @@ -879,6 +879,9 @@ static void __remove_hrtimer(struct hrtimer *timer, next_timer = timerqueue_getnext(&base->active); timerqueue_del(&base->active, &timer->node); + if (!timerqueue_getnext(&base->active)) + base->cpu_base->active_bases &= ~(1 << base->index); + if (&timer->node == next_timer) { #ifdef CONFIG_HIGH_RES_TIMERS /* Reprogram the clock event device. if enabled */ @@ -892,8 +895,6 @@ static void __remove_hrtimer(struct hrtimer *timer, } #endif } - if (!timerqueue_getnext(&base->active)) - base->cpu_base->active_bases &= ~(1 << base->index); out: timer->state = newstate; } -- 2.3.0.rc0.44.ga94655d