Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751491AbWAWQ3o (ORCPT ); Mon, 23 Jan 2006 11:29:44 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751479AbWAWQ3o (ORCPT ); Mon, 23 Jan 2006 11:29:44 -0500 Received: from gw1.cosmosbay.com ([62.23.185.226]:45499 "EHLO gw1.cosmosbay.com") by vger.kernel.org with ESMTP id S1751491AbWAWQ3n (ORCPT ); Mon, 23 Jan 2006 11:29:43 -0500 Message-ID: <43D50445.1080208@cosmosbay.com> Date: Mon, 23 Jan 2006 17:28:53 +0100 From: Eric Dumazet User-Agent: Thunderbird 1.5 (Windows/20051201) MIME-Version: 1.0 To: Andi Kleen CC: pravin shelar , Ravikiran G Thirumalai , Shai Fultheim , linux-kernel@vger.kernel.org, "David S. Miller" Subject: Re: [PATCH] garbage values in file /proc/net/sockstat References: <200601231224.16196.ak@suse.de> <43D4DA15.4010009@cosmosbay.com> <200601231611.51326.ak@suse.de> In-Reply-To: <200601231611.51326.ak@suse.de> Content-Type: multipart/mixed; boundary="------------060106070403080906010605" X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-1.6 (gw1.cosmosbay.com [172.16.8.80]); Mon, 23 Jan 2006 17:28:53 +0100 (CET) Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3595 Lines: 98 This is a multi-part message in MIME format. --------------060106070403080906010605 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 8bit Andi Kleen a ?crit : > On Monday 23 January 2006 14:28, Eric Dumazet wrote: > >> Shouldnt we force a page fault for not possible cpus in cpu_data >> to catch all access to per_cpu(some_object, some_not_possible_cpu) ? >> >> We can use a red zone big enough to hold the whole per_cpu data. > > Good idea. Can you please send me a tested patch? > I did a patch (on top of 2.6.16-rc1-mm2) , but the kernel crashes in sched_init(void) for (i = 0; i < NR_CPUS; i++) { prio_array_t *array; rq = cpu_rq(i); spin_lock_init(&rq->lock); <<-CRASH In my config, NR_CPUS = 8, and I have one only one CPU inside my test box. So should I send only the patch or all the corrections I have to do to avoid all possible crashes in my config ? Thank you Eric Dumazet [PATCH] x86_64 : Use a special CPUDATA_RED_ZONE to catch accesses to per_cpu(some_object, some_not_possible_cpu) Because cpu_data(cpu)->data_offset may contain garbage, some buggy code may do random things without notice. If we initialize data_offset so that the per_cpu() data sits in an unmapped memory area, we should get page faults and stack traces should help us find the bugs. Signed-off-by: Eric Dumazet --------------060106070403080906010605 Content-Type: text/plain; name="cpudata_red_zone.patch" Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="cpudata_red_zone.patch" --- linux-2.6.16-rc1/Documentation/x86_64/mm.txt 2006-01-17 08:44:47.000000000 +0100 +++ linux-2.6.16-rc1-mm2-ed/Documentation/x86_64/mm.txt 2006-01-23 16:54:46.000000000 +0100 @@ -5,7 +5,8 @@ 0000000000000000 - 00007fffffffffff (=47bits) user space, different per mm hole caused by [48:63] sign extension -ffff800000000000 - ffff80ffffffffff (=40bits) guard hole +ffff800000000000 - ffff807fffffffff (=39bits) guard hole +ffff808000000000 - ffff80ffffffffff (=39bits) not possible cpus percpudata hole ffff810000000000 - ffffc0ffffffffff (=46bits) direct mapping of all phys. memory ffffc10000000000 - ffffc1ffffffffff (=40bits) hole ffffc20000000000 - ffffe1ffffffffff (=45bits) vmalloc/ioremap space --- linux-2.6.16-rc1/include/asm-x86_64/pgtable.h 2006-01-17 08:44:47.000000000 +0100 +++ linux-2.6.16-rc1-mm2-ed/include/asm-x86_64/pgtable.h 2006-01-23 16:54:46.000000000 +0100 @@ -136,6 +136,7 @@ #ifndef __ASSEMBLY__ #define MAXMEM 0x3fffffffffffUL +#define CPUDATA_RED_ZONE 0xffff808000000000UL #define VMALLOC_START 0xffffc20000000000UL #define VMALLOC_END 0xffffe1ffffffffffUL #define MODULES_VADDR 0xffffffff88000000UL --- linux-2.6.16-rc1/arch/x86_64/kernel/setup64.c 2006-01-23 16:36:38.000000000 +0100 +++ linux-2.6.16-rc1-mm2-ed/arch/x86_64/kernel/setup64.c 2006-01-23 16:58:30.000000000 +0100 @@ -99,9 +99,13 @@ size = PERCPU_ENOUGH_ROOM; #endif - for_each_cpu_mask (i, cpu_possible_map) { + for (i = 0 ; i < NR_CPUS ; i++) { char *ptr; + cpu_pda(i)->data_offset = (char *)CPUDATA_RED_ZONE - __per_cpu_start; + if (!cpu_possible(i)) + continue; + if (!NODE_DATA(cpu_to_node(i))) { printk("cpu with no node %d, num_online_nodes %d\n", i, num_online_nodes()); --------------060106070403080906010605-- - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/