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=-9.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,URIBL_BLOCKED, USER_AGENT_GIT 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 67193C04EB9 for ; Mon, 3 Dec 2018 17:28:36 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 3D6DA2087F for ; Mon, 3 Dec 2018 17:28:36 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 3D6DA2087F Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726905AbeLCR2j (ORCPT ); Mon, 3 Dec 2018 12:28:39 -0500 Received: from foss.arm.com ([217.140.101.70]:42910 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725852AbeLCR2h (ORCPT ); Mon, 3 Dec 2018 12:28:37 -0500 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.72.51.249]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id ABC44168F; Mon, 3 Dec 2018 09:28:32 -0800 (PST) Received: from e110467-lin.cambridge.arm.com (e110467-lin.cambridge.arm.com [10.1.196.75]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPA id 55A2A3F59C; Mon, 3 Dec 2018 09:28:31 -0800 (PST) From: Robin Murphy To: hch@lst.de Cc: m.szyprowski@samsung.com, iommu@lists.linux-foundation.org, linux-kernel@vger.kernel.org, cai@gmx.us, salil.mehta@huawei.com, john.garry@huawei.com Subject: [RFC 4/4] dma-debug: Make leak-like behaviour apparent Date: Mon, 3 Dec 2018 17:28:09 +0000 Message-Id: <7ec928f0bd92122f271c421e99aaeb593ccabdf5.1543856576.git.robin.murphy@arm.com> X-Mailer: git-send-email 2.19.1.dirty In-Reply-To: References: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Now that we can dynamically allocate DMA debug entries to cope with drivers maintaining excessively large numbers of live mappings, a driver which *does* actually have a bug leaking mappings (and is not unloaded) will no longer trigger the "DMA-API: debugging out of memory - disabling" message until it gets to actual kernel OOM conditions, which means it could go unnoticed for a while. To that end, let's inform the user each time the pool has grown to a multiple of its initial size, which should make it apparent that they either have a leak or might want to increase the preallocation size. Signed-off-by: Robin Murphy --- Tagging this one as RFC since people might think it's silly. kernel/dma/debug.c | 15 ++++++++++++++- 1 file changed, 14 insertions(+), 1 deletion(-) diff --git a/kernel/dma/debug.c b/kernel/dma/debug.c index 46cc075aec99..c4759dab0f8c 100644 --- a/kernel/dma/debug.c +++ b/kernel/dma/debug.c @@ -696,6 +696,17 @@ static struct dma_debug_entry *__dma_entry_alloc(void) return entry; } +void __dma_entry_alloc_check_leak(void) +{ + u32 tmp = nr_total_entries % nr_prealloc_entries; + + /* Shout each time we tick over some multiple of the initial pool */ + if (tmp < DMA_DEBUG_DYNAMIC_ENTRIES) { + pr_info("dma_debug_entry pool grown to %u00%% - possible mapping leak?\n", + (nr_total_entries / nr_prealloc_entries)); + } +} + /* struct dma_entry allocator * * The next two functions implement the allocator for @@ -716,8 +727,10 @@ static struct dma_debug_entry *dma_entry_alloc(void) spin_unlock_irqrestore(&free_entries_lock, flags); if (retry_count < DMA_DEBUG_DYNAMIC_RETRIES && - !prealloc_memory(DMA_DEBUG_DYNAMIC_ENTRIES)) + !prealloc_memory(DMA_DEBUG_DYNAMIC_ENTRIES)) { + __dma_entry_alloc_check_leak(); continue; + } global_disable = true; pr_err("debugging out of memory - disabling\n"); -- 2.19.1.dirty