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,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 344A8C04EB9 for ; Wed, 5 Dec 2018 19:57:37 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id F26D820989 for ; Wed, 5 Dec 2018 19:57:36 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org F26D820989 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 S1728746AbeLET5S (ORCPT ); Wed, 5 Dec 2018 14:57:18 -0500 Received: from usa-sjc-mx-foss1.foss.arm.com ([217.140.101.70]:34520 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728716AbeLET5Q (ORCPT ); Wed, 5 Dec 2018 14:57:16 -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 BE906EBD; Wed, 5 Dec 2018 11:57:15 -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 67D313F614; Wed, 5 Dec 2018 11:57:14 -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: [PATCH v2 4/8] dma-debug: Dynamically expand the dma_debug_entry pool Date: Wed, 5 Dec 2018 19:56:53 +0000 Message-Id: <8ba34734842beb3ef72260c4ab822dba7c588e4c.1544037783.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 Certain drivers such as large multi-queue network adapters can use pools of mapped DMA buffers larger than the default dma_debug_entry pool of 65536 entries, with the result that merely probing such a device can cause DMA debug to disable itself during boot unless explicitly given an appropriate "dma_debug_entries=..." option. Developers trying to debug some other driver on such a system may not be immediately aware of this, and at worst it can hide bugs if they fail to realise that dma-debug has already disabled itself unexpectedly by the time the code of interest gets to run. Even once they do realise, it can be a bit of a pain to emprirically determine a suitable number of preallocated entries to configure without massively over-allocating. There's really no need for such a static limit, though, since we can quite easily expand the pool at runtime in those rare cases that the preallocated entries are insufficient, which is arguably the least surprising and most useful behaviour. Signed-off-by: Robin Murphy --- v2: Use GFP_ATOMIC, make retry loop redundant, update documentation Documentation/DMA-API.txt | 11 +++++------ kernel/dma/debug.c | 15 +++++++++------ 2 files changed, 14 insertions(+), 12 deletions(-) diff --git a/Documentation/DMA-API.txt b/Documentation/DMA-API.txt index 6bdb095393b0..0fcb7561af1e 100644 --- a/Documentation/DMA-API.txt +++ b/Documentation/DMA-API.txt @@ -717,8 +717,8 @@ dma-api/num_errors The number in this file shows how many dma-api/min_free_entries This read-only file can be read to get the minimum number of free dma_debug_entries the allocator has ever seen. If this value goes - down to zero the code will disable itself - because it is not longer reliable. + down to zero the code will attempt to increase + nr_total_entries to compensate. dma-api/num_free_entries The current number of free dma_debug_entries in the allocator. @@ -745,10 +745,9 @@ driver filter at boot time. The debug code will only print errors for that driver afterwards. This filter can be disabled or changed later using debugfs. When the code disables itself at runtime this is most likely because it ran -out of dma_debug_entries. These entries are preallocated at boot. The number -of preallocated entries is defined per architecture. If it is too low for you -boot with 'dma_debug_entries=' to overwrite the -architectural default. +out of dma_debug_entries and was unable to allocate more on-demand. 65536 +entries are preallocated at boot - if this is too low for you boot with +'dma_debug_entries=' to overwrite the default. :: diff --git a/kernel/dma/debug.c b/kernel/dma/debug.c index 1b0858d7edfd..b1fe8b78acc4 100644 --- a/kernel/dma/debug.c +++ b/kernel/dma/debug.c @@ -47,6 +47,8 @@ #ifndef PREALLOC_DMA_DEBUG_ENTRIES #define PREALLOC_DMA_DEBUG_ENTRIES (1 << 16) #endif +/* If the pool runs out, add this many new entries at once */ +#define DMA_DEBUG_DYNAMIC_ENTRIES 256 enum { dma_debug_single, @@ -702,12 +704,13 @@ static struct dma_debug_entry *dma_entry_alloc(void) unsigned long flags; spin_lock_irqsave(&free_entries_lock, flags); - - if (list_empty(&free_entries)) { - global_disable = true; - spin_unlock_irqrestore(&free_entries_lock, flags); - pr_err("debugging out of memory - disabling\n"); - return NULL; + if (num_free_entries == 0) { + if (dma_debug_create_entries(DMA_DEBUG_DYNAMIC_ENTRIES, GFP_ATOMIC)) { + global_disable = true; + spin_unlock_irqrestore(&free_entries_lock, flags); + pr_err("debugging out of memory - disabling\n"); + return NULL; + } } entry = __dma_entry_alloc(); -- 2.19.1.dirty