From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-11.8 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, MENTIONS_GIT_HOSTING,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id BD82BC31E46 for ; Wed, 12 Jun 2019 12:28:31 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 9491420874 for ; Wed, 12 Jun 2019 12:28:31 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=zytor.com header.i=@zytor.com header.b="OcvV0ncR" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732389AbfFLM2a (ORCPT ); Wed, 12 Jun 2019 08:28:30 -0400 Received: from terminus.zytor.com ([198.137.202.136]:49179 "EHLO terminus.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727047AbfFLM23 (ORCPT ); Wed, 12 Jun 2019 08:28:29 -0400 Received: from terminus.zytor.com (localhost [127.0.0.1]) by terminus.zytor.com (8.15.2/8.15.2) with ESMTPS id x5CCSN5Z685191 (version=TLSv1.3 cipher=TLS_AES_256_GCM_SHA384 bits=256 verify=NO); Wed, 12 Jun 2019 05:28:23 -0700 DKIM-Filter: OpenDKIM Filter v2.11.0 terminus.zytor.com x5CCSN5Z685191 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=zytor.com; s=2019051801; t=1560342503; bh=oIVJEOdoZvmVLvEi4yi8nrOfcAuXixs2rt9tEVgfEtU=; h=Date:From:Cc:Reply-To:In-Reply-To:References:To:Subject:From; b=OcvV0ncRZ5kVRTKkJjgfrKUnu9qGDuRZmGtU+0U3HXq9v38uoZqUaECIGAzJ6v9AI K4gpbmajCHoZz0501xE/0g/pt5tmtt1kcUymZjHW+P4MP4oNn+fqbSlavEBhTRqtts cG55BlRwgBLJNRE4sH/GXd0YcKUMFMO2o/3Or9lHv+Fi9+aoqRt0NnV8OlXbcl7z7S wKoJ16g9y/P1FBkG6fbfsKD/xvTSQoPcmPSvqEKJomvNSgeOtUHg2XRJzro99PNzrH 4eCazQApEcRXk2xDSTy3tB5mAIOppFHFzLxn0vNQT7jU1fXuBZDnDir4PIOUN4Slll 6zBcXISctsiXg== Received: (from tipbot@localhost) by terminus.zytor.com (8.15.2/8.15.2/Submit) id x5CCSM7J685188; Wed, 12 Jun 2019 05:28:22 -0700 Date: Wed, 12 Jun 2019 05:28:22 -0700 X-Authentication-Warning: terminus.zytor.com: tipbot set sender to tipbot@zytor.com using -f From: tip-bot for Daniel Lezcano Message-ID: Cc: linux-kernel@vger.kernel.org, hpa@zytor.com, mingo@kernel.org, daniel.lezcano@linaro.org, tglx@linutronix.de Reply-To: linux-kernel@vger.kernel.org, tglx@linutronix.de, daniel.lezcano@linaro.org, mingo@kernel.org, hpa@zytor.com In-Reply-To: <20190527205521.12091-3-daniel.lezcano@linaro.org> References: <20190527205521.12091-3-daniel.lezcano@linaro.org> To: linux-tip-commits@vger.kernel.org Subject: [tip:irq/core] genirq/timings: Fix timings buffer inspection Git-Commit-ID: 2840eef0513c518faeb8a0ab8d07268c6285cdd0 X-Mailer: tip-git-log-daemon Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Content-Type: text/plain; charset=UTF-8 Content-Disposition: inline Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Commit-ID: 2840eef0513c518faeb8a0ab8d07268c6285cdd0 Gitweb: https://git.kernel.org/tip/2840eef0513c518faeb8a0ab8d07268c6285cdd0 Author: Daniel Lezcano AuthorDate: Mon, 27 May 2019 22:55:15 +0200 Committer: Thomas Gleixner CommitDate: Wed, 12 Jun 2019 10:47:03 +0200 genirq/timings: Fix timings buffer inspection It appears the index beginning computation is not correct, the current code does: i = (irqts->count & IRQ_TIMINGS_MASK) - 1 If irqts->count is equal to zero, we end up with an index equal to -1, but that does not happen because the function checks against zero before and returns in such case. However, if irqts->count is a multiple of IRQ_TIMINGS_SIZE, the resulting & bit op will be zero and leads also to a -1 index. Re-introduce the iteration loop belonging to the previous variance code which was correct. Fixes: bbba0e7c5cda "genirq/timings: Add array suffix computation code" Signed-off-by: Daniel Lezcano Signed-off-by: Thomas Gleixner Cc: andriy.shevchenko@linux.intel.com Link: https://lkml.kernel.org/r/20190527205521.12091-3-daniel.lezcano@linaro.org --- kernel/irq/timings.c | 23 ++++++++++++++++++----- 1 file changed, 18 insertions(+), 5 deletions(-) diff --git a/kernel/irq/timings.c b/kernel/irq/timings.c index 4f5daf3db13b..19d2fad379ee 100644 --- a/kernel/irq/timings.c +++ b/kernel/irq/timings.c @@ -267,6 +267,23 @@ void irq_timings_disable(void) #define PREDICTION_MAX 10 /* 2 ^ PREDICTION_MAX useconds */ #define PREDICTION_BUFFER_SIZE 16 /* slots for EMAs, hardly more than 16 */ +/* + * Number of elements in the circular buffer: If it happens it was + * flushed before, then the number of elements could be smaller than + * IRQ_TIMINGS_SIZE, so the count is used, otherwise the array size is + * used as we wrapped. The index begins from zero when we did not + * wrap. That could be done in a nicer way with the proper circular + * array structure type but with the cost of extra computation in the + * interrupt handler hot path. We choose efficiency. + */ +#define for_each_irqts(i, irqts) \ + for (i = irqts->count < IRQ_TIMINGS_SIZE ? \ + 0 : irqts->count & IRQ_TIMINGS_MASK, \ + irqts->count = min(IRQ_TIMINGS_SIZE, \ + irqts->count); \ + irqts->count > 0; irqts->count--, \ + i = (i + 1) & IRQ_TIMINGS_MASK) + struct irqt_stat { u64 last_ts; u64 ema_time[PREDICTION_BUFFER_SIZE]; @@ -526,11 +543,7 @@ u64 irq_timings_next_event(u64 now) * model while decrementing the counter because we consume the * data from our circular buffer. */ - - i = (irqts->count & IRQ_TIMINGS_MASK) - 1; - irqts->count = min(IRQ_TIMINGS_SIZE, irqts->count); - - for (; irqts->count > 0; irqts->count--, i = (i + 1) & IRQ_TIMINGS_MASK) { + for_each_irqts(i, irqts) { irq = irq_timing_decode(irqts->values[i], &ts); s = idr_find(&irqt_stats, irq); if (s)