Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756180AbaKROeg (ORCPT ); Tue, 18 Nov 2014 09:34:36 -0500 Received: from cantor2.suse.de ([195.135.220.15]:57215 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755094AbaKROKM (ORCPT ); Tue, 18 Nov 2014 09:10:12 -0500 From: Jiri Slaby To: stable@vger.kernel.org Cc: linux-kernel@vger.kernel.org, Thomas Gleixner , Sebastian Andrzej Siewior , Felipe Balbi , Jiri Slaby Subject: [PATCH 3.12 158/206] usb: musb: cppi41: restart hrtimer only if not yet done Date: Tue, 18 Nov 2014 15:08:33 +0100 Message-Id: X-Mailer: git-send-email 2.1.3 In-Reply-To: <28f04bcc068a44c5641c727883947960fb8dcbd5.1416319692.git.jslaby@suse.cz> References: <28f04bcc068a44c5641c727883947960fb8dcbd5.1416319692.git.jslaby@suse.cz> In-Reply-To: References: Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Thomas Gleixner 3.12-stable review patch. If anyone has any objections, please let me know. =============== commit d2e6d62c9cbbc2da4211f672dbeea08960e29a80 upstream. commit c58d80f52 ("usb: musb: Ensure that cppi41 timer gets armed on premature DMA TX irq") fixed hrtimer scheduling bug. There is one left which does not trigger that often. The following scenario is still possible: lock(&x->lock); hrtimer_start(&x->t); unlock(&x->lock); expires: t->function(); lock(&x->lock); lock(&x->lock); if (!hrtimer_queued(&x->t)) hrtimer_start(&x->t); unlock(&x->lock); if (!list_empty(x->early_tx_list)) ret = HRTIMER_RESTART; -> hrtimer_forward_now(...) } else ret = HRTIMER_NORESTART; unlock(&x->lock); and the timer callback returns HRTIMER_RESTART for an armed timer. This is wrong and we run into the BUG_ON() in __run_hrtimer(). This can happens on SMP or PREEMPT-RT. The patch fixes the problem by only starting the timer if the timer is not yet queued. Reported-by: Torben Hohn Signed-off-by: Thomas Gleixner [bigeasy: collected information and created a patch + description based on it] Signed-off-by: Sebastian Andrzej Siewior Signed-off-by: Felipe Balbi Signed-off-by: Jiri Slaby --- drivers/usb/musb/musb_cppi41.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/drivers/usb/musb/musb_cppi41.c b/drivers/usb/musb/musb_cppi41.c index bd6cc0bea150..5c91ff379345 100644 --- a/drivers/usb/musb/musb_cppi41.c +++ b/drivers/usb/musb/musb_cppi41.c @@ -190,7 +190,8 @@ static enum hrtimer_restart cppi41_recheck_tx_req(struct hrtimer *timer) } } - if (!list_empty(&controller->early_tx_list)) { + if (!list_empty(&controller->early_tx_list) && + !hrtimer_is_queued(&controller->early_tx)) { ret = HRTIMER_RESTART; hrtimer_forward_now(&controller->early_tx, ktime_set(0, 50 * NSEC_PER_USEC)); -- 2.1.3 -- 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/