From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751441AbZH1CdF (ORCPT ); Thu, 27 Aug 2009 22:33:05 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1750969AbZH1CdD (ORCPT ); Thu, 27 Aug 2009 22:33:03 -0400 Received: from wa-out-1112.google.com ([209.85.146.181]:56207 "EHLO wa-out-1112.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750848AbZH1CdB convert rfc822-to-8bit (ORCPT ); Thu, 27 Aug 2009 22:33:01 -0400 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=mime-version:sender:in-reply-to:references:date :x-google-sender-auth:message-id:subject:from:to:cc:content-type :content-transfer-encoding; b=cS/Mqmhw44JrY1z3NG5oWxsi8P3YUs5qd0cQ+8n6y7MNW6IQHGJKtUAEpuVnVIeSvd P1u2npNR6nV77cG7k3xj7/HHuzncLfkEA7/PxIf3kRQG4cBEpnALuCLWCfuGQhlDvA7y oKtTEGv0PGqz16ra63ZO6UnFv+LOseH1paoqA= MIME-Version: 1.0 In-Reply-To: <20090828015032.GA13271@localhost> References: <4A9677C1.3090804@gmail.com> <20090827122144.GA20443@localhost> <3d0408630908270946n7302e3c5u94f133d8ebbe8c36@mail.gmail.com> <20090828015032.GA13271@localhost> Date: Fri, 28 Aug 2009 10:33:03 +0800 X-Google-Sender-Auth: e2c9efac588387b1 Message-ID: <3d0408630908271933v1d136b85he33e7d4b6e0bccf6@mail.gmail.com> Subject: Re: [PATCH] Make radix_tree_preload alloc one more slot From: "Yan, Zheng " To: Wu Fengguang Cc: Zhu Yanhai , Andrew Morton , Jiri Kosina , Huang Shijie , "linux-kernel@vger.kernel.org" , Zhu Yanhai , Nick Piggin Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 2009/8/28 Wu Fengguang : > On Fri, Aug 28, 2009 at 12:46:46AM +0800, Yan, Zheng  wrote: >> 2009/8/27 Wu Fengguang : >> > >> > Hi Yanhai, >> > >> > [Nick CCed] >> > >> > On Thu, Aug 27, 2009 at 08:10:41PM +0800, Zhu Yanhai wrote: >> >> The operations against radix tree always use paths with RADIX_TREE_MAX_PATH >> >> + 1 slots, but radix_tree_preload only pre-allocs RADIX_TREE_MAX_PATH >> >> slots at present, which causes radix_tree_node_alloc tries to do >> >> kmem_cache_alloc at the last slot even if we don't have gfp_mask & >> >> __GFP_WAIT in hand. >> > >> > Are you sure?  The comments read: >> > >> >        /* >> >         * The radix tree path needs to be one longer than the maximum path >> >         * since the "list" is null terminated. >> >         */ >> >        struct radix_tree_path path[RADIX_TREE_MAX_PATH + 1], *pathp = path; >> > >> > Thanks, >> > Fengguang >> > >> > >> >> Signed-off-by: Zhu Yanhai >> >> >> >> --- >> >>  lib/radix-tree.c |    2 +- >> >>  1 files changed, 1 insertions(+), 1 deletions(-) >> >> >> >> diff --git a/lib/radix-tree.c b/lib/radix-tree.c >> >> index 23abbd9..72225a8 100644 >> >> --- a/lib/radix-tree.c >> >> +++ b/lib/radix-tree.c >> >> @@ -79,7 +79,7 @@ static struct kmem_cache *radix_tree_node_cachep; >> >>   */ >> >>  struct radix_tree_preload { >> >>       int nr; >> >> -     struct radix_tree_node *nodes[RADIX_TREE_MAX_PATH]; >> >> +     struct radix_tree_node *nodes[RADIX_TREE_MAX_PATH + 1]; >> >>  }; >> >>  static DEFINE_PER_CPU(struct radix_tree_preload, radix_tree_preloads) = { 0, }; >> >> >> >> -- >> >> 1.6.2.2 >> >> here is test case. >> --- >> #include >> #include >> #include >> >> static void __exit exit_test(void) >> { >> } >> >> static int __init init_test(void) >> { >>         struct radix_tree_root radix_tree; >>         int foo; >> >>         INIT_RADIX_TREE(&radix_tree, GFP_KERNEL); >>         radix_tree_preload(GFP_KERNEL); >>         preempt_disable(); >>         radix_tree_insert(&radix_tree, (unsigned long)-2, &foo); >>         preempt_enable(); >>         radix_tree_preload_end(); >>         radix_tree_delete(&radix_tree, (unsigned long)-2); >>         return -1; >> } >> >> module_init(init_test) >> module_exit(exit_test) >> MODULE_LICENSE("GPL"); >> -- end -- >> >> I got following oops. >> --- >> BUG: sleeping function called from invalid context at >> /home/zhyan/linux-2.6/mm/slub.c:1697 >> in_atomic(): 1, irqs_disabled(): 0, pid: 2791, name: insmod >> Pid: 2791, comm: insmod Not tainted 2.6.31-rc7 #1 >> Call Trace: >>  [] __might_sleep+0x101/0x108 >>  [] kmem_cache_alloc+0x39/0x141 >>  [] ? radix_tree_node_alloc+0x4c/0x5d >>  [] radix_tree_node_alloc+0x4c/0x5d >>  [] radix_tree_insert+0xc2/0x174 >>  [] init_test+0x3f/0x89 [test] >>  [] do_one_initcall+0x4f/0x11f >>  [] ? init_test+0x0/0x89 [test] >>  [] ? __blocking_notifier_call_chain+0x45/0x51 >>  [] sys_init_module+0xac/0x1bc >>  [] sysenter_do_call+0x12/0x2d >> -- end -- > This is weird, I cannot reproduce this message. Here is my .config. > I use SLAB but it also has the might_sleep_if(__GFP_WAIT) debug call. > Thanks, > Fengguang I realize it's my fault, I use GFP_KERNEL to initialize the radix tree. radix_tree_node_alloc does not use pre-loaded memory when the radix tree is initialized with GFP_KERNEL. Yesterday when I saw the Oops, I suspect it's an radix_tree_preload bug. I told Zhu Yanhai my thought. Please forgive my rash act. Regards Yan, Zheng