From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Ben Skeggs Subject: [PATCH 4.9 054/164] drm/nouveau/tmr: handle races with hw when updating the next alarm time Date: Tue, 23 May 2017 22:07:51 +0200 Message-Id: <20170523200909.539850341@linuxfoundation.org> In-Reply-To: <20170523200907.297534241@linuxfoundation.org> References: <20170523200907.297534241@linuxfoundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: 4.9-stable review patch. If anyone has any objections, please let me know. ------------------ From: Ben Skeggs commit 1b0f84380b10ee97f7d2dd191294de9017e94d1d upstream. If the time to the next alarm is short enough, we could race with HW and end up with an ~4 second delay until it triggers. Fix this by checking again after we update HW. Signed-off-by: Ben Skeggs Signed-off-by: Greg Kroah-Hartman --- drivers/gpu/drm/nouveau/nvkm/subdev/timer/base.c | 26 ++++++++++++++--------- 1 file changed, 16 insertions(+), 10 deletions(-) --- a/drivers/gpu/drm/nouveau/nvkm/subdev/timer/base.c +++ b/drivers/gpu/drm/nouveau/nvkm/subdev/timer/base.c @@ -36,23 +36,29 @@ nvkm_timer_alarm_trigger(struct nvkm_tim unsigned long flags; LIST_HEAD(exec); - /* move any due alarms off the pending list */ + /* Process pending alarms. */ spin_lock_irqsave(&tmr->lock, flags); list_for_each_entry_safe(alarm, atemp, &tmr->alarms, head) { - if (alarm->timestamp <= nvkm_timer_read(tmr)) - list_move_tail(&alarm->head, &exec); + /* Have we hit the earliest alarm that hasn't gone off? */ + if (alarm->timestamp > nvkm_timer_read(tmr)) { + /* Schedule it. If we didn't race, we're done. */ + tmr->func->alarm_init(tmr, alarm->timestamp); + if (alarm->timestamp > nvkm_timer_read(tmr)) + break; + } + + /* Move to completed list. We'll drop the lock before + * executing the callback so it can reschedule itself. + */ + list_move_tail(&alarm->head, &exec); } - /* reschedule interrupt for next alarm time */ - if (!list_empty(&tmr->alarms)) { - alarm = list_first_entry(&tmr->alarms, typeof(*alarm), head); - tmr->func->alarm_init(tmr, alarm->timestamp); - } else { + /* Shut down interrupt if no more pending alarms. */ + if (list_empty(&tmr->alarms)) tmr->func->alarm_fini(tmr); - } spin_unlock_irqrestore(&tmr->lock, flags); - /* execute any pending alarm handlers */ + /* Execute completed callbacks. */ list_for_each_entry_safe(alarm, atemp, &exec, head) { list_del_init(&alarm->head); alarm->func(alarm);