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 AE9C1C04EB9 for ; Mon, 3 Dec 2018 17:28:33 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 81E2120850 for ; Mon, 3 Dec 2018 17:28:33 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 81E2120850 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 S1726882AbeLCR2h (ORCPT ); Mon, 3 Dec 2018 12:28:37 -0500 Received: from foss.arm.com ([217.140.101.70]:42898 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725852AbeLCR2g (ORCPT ); Mon, 3 Dec 2018 12:28:36 -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 187B11713; Mon, 3 Dec 2018 09:28:31 -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 B66803F59C; Mon, 3 Dec 2018 09:28:29 -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 3/4] dma-debug: Dynamically expand the dma_debug_entry pool Date: Mon, 3 Dec 2018 17:28:08 +0000 Message-Id: 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 --- kernel/dma/debug.c | 18 +++++++++++++++--- 1 file changed, 15 insertions(+), 3 deletions(-) diff --git a/kernel/dma/debug.c b/kernel/dma/debug.c index de5db800dbfc..46cc075aec99 100644 --- a/kernel/dma/debug.c +++ b/kernel/dma/debug.c @@ -47,6 +47,9 @@ #ifndef PREALLOC_DMA_DEBUG_ENTRIES #define PREALLOC_DMA_DEBUG_ENTRIES (1 << 16) #endif +/* If the pool runs out, try this many times to allocate this many new entries */ +#define DMA_DEBUG_DYNAMIC_ENTRIES 256 +#define DMA_DEBUG_DYNAMIC_RETRIES 2 enum { dma_debug_single, @@ -702,12 +705,21 @@ static struct dma_debug_entry *dma_entry_alloc(void) { struct dma_debug_entry *entry; unsigned long flags; + int retry_count; - spin_lock_irqsave(&free_entries_lock, flags); + for (retry_count = 0; ; retry_count++) { + spin_lock_irqsave(&free_entries_lock, flags); + + if (num_free_entries > 0) + break; - if (list_empty(&free_entries)) { - global_disable = true; spin_unlock_irqrestore(&free_entries_lock, flags); + + if (retry_count < DMA_DEBUG_DYNAMIC_RETRIES && + !prealloc_memory(DMA_DEBUG_DYNAMIC_ENTRIES)) + continue; + + global_disable = true; pr_err("debugging out of memory - disabling\n"); return NULL; } -- 2.19.1.dirty