Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751804AbaL2B4r (ORCPT ); Sun, 28 Dec 2014 20:56:47 -0500 Received: from mail-ob0-f171.google.com ([209.85.214.171]:47010 "EHLO mail-ob0-f171.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751534AbaL2B4p (ORCPT ); Sun, 28 Dec 2014 20:56:45 -0500 MIME-Version: 1.0 In-Reply-To: References: Date: Mon, 29 Dec 2014 09:56:44 +0800 Message-ID: Subject: Re: panic at rb_next when do pick_next_task_fair because of rb_leftmost is NULL From: Neil Zhang To: LKML Cc: Ingo Molnar , peterz@infradead.org Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Does anyone ever encountered it? Please give your help if any. Thanks in advanced! Best Regards, Neil Zhang 2014-12-26 17:37 GMT+08:00 Neil Zhang : > Hi All, > I encountered the following crash in 3.10.24. > > The panic log is as following. > The strange thing is that the nr_running change to NULL after pass the > check in the beginning of pick_next_task_fair. > So it seems there are race condition in the code. > Seems no related patch to fix it in the mainline. > Does anyone can help it? > > struct rq { > lock = { > raw_lock = { > { > slock = 1463113524, > tickets = { > owner = 22324, > next = 22325 > } > } > } > }, > nr_running = 0, > cpu_load = {0, 0, 3, 33, 72}, > last_load_update_tick = 83021764, > nohz_stamp = 0, > nohz_flags = 1, > skip_clock_update = 0, > nr_last_stamp = 83321795255303, > nr_running_integral = 54283347762368512, > ave_seqcnt = { > sequence = 690446180 > }, > load = { > weight = 0, > inv_weight = 0 > }, > nr_load_updates = 51751174, > nr_switches = 290795987, > cfs = { > load = { > weight = 0, > inv_weight = 0 > }, > nr_running = 0, > h_nr_running = 0, > exec_clock = 17025953367624, > min_vruntime = 125082978146967, > min_vruntime_copy = 125082978146967, > tasks_timeline = { > rb_node = 0x0 > }, > rb_leftmost = 0x0, > curr = 0x0, > next = 0x0, > last = 0x0, > skip = 0x0, > nr_spread_over = 57488, > runnable_load_avg = 0, > > [83321.795281] c0 2084 (v.airplayserver) Unable to handle kernel NULL > pointer dereference at virtual address 00000008 > [83321.795286] c0 2084 (v.airplayserver) pgd = ea858000 > [83321.795293] c0 2084 (v.airplayserver) [00000008] *pgd=00000000 > [83321.795306] c0 2084 (v.airplayserver) Internal error: Oops: 205 > [#1] PREEMPT SMP ARM > [83321.795315] c0 2084 (v.airplayserver) Modules linked in: > [83321.795324] c0 2084 (v.airplayserver) CPU: 0 PID: 2084 Comm: > v.airplayserver Not tainted 3.10.24-gc7b472f #1 > [83321.795329] c0 2084 (v.airplayserver) task: ce1f1ac0 ti: ce156000 > task.ti: ce156000 > [83321.795349] c0 2084 (v.airplayserver) PC is at rb_next+0x0/0x60 > [83321.795363] c0 2084 (v.airplayserver) LR is at > pick_next_task_fair+0x10c/0x138 > [83321.795368] c0 2084 (v.airplayserver) pc : [] lr : > [] psr: 60060093 > sp : ce157e18 ip : 00000000 fp : ce157edc > [83321.795371] c0 2084 (v.airplayserver) r10: c54474c0 r9 : c0c644c0 > r8 : ce157f20 > [83321.795376] c0 2084 (v.airplayserver) r7 : c54474c0 r6 : 00000000 > r5 : 00000000 r4 : c5447518 > [83321.795380] c0 2084 (v.airplayserver) r3 : c0097294 r2 : c54478f8 > r1 : 00000000 r0 : 00000008 > [83321.795388] c0 2084 (v.airplayserver) Flags: nZCv IRQs off FIQs on > Mode SVC_32 ISA ARM Segment user > [83321.795392] c0 2084 (v.airplayserver) Control: 30c5387d Table: > aa858000 DAC: fffffffd > [83321.795396] c0 2084 (v.airplayserver) > PC: 0xc02c2270: > [83321.795419] c0 2084 (v.airplayserver) 2270 1a000001 ea000004 > e1a00003 e5903004 e3530000 1afffffb e12fff1e e12fff1e > [83321.795439] c0 2084 (v.airplayserver) 2290 e1a03001 e5901000 > e3d11003 05823000 0a000003 e5912008 e1500002 05813008 > [83321.795461] c0 2084 (v.airplayserver) 22b0 15813004 e5902008 > e3520000 15921000 12011001 11831001 15821000 e5902004 > [83321.795483] c0 2084 (v.airplayserver) 22d0 e3520000 15921000 > 12011001 11831001 15821000 e8900007 e8830007 e12fff1e > [83321.795504] c0 2084 (v.airplayserver) 22f0 e5902000 e1500002 > 0a000012 e5903004 e3530000 1a000001 ea000006 e1a03002 > [83321.795526] c0 2084 (v.airplayserver) 2310 e5932008 e3520000 > 1afffffb e1a00003 e12fff1e e5932000 e3d23003 0afffffa > [83321.795546] c0 2084 (v.airplayserver) 2330 e5932004 e1500002 > e1a00003 0afffff8 e1a00003 e12fff1e e3a03000 eafffff2 > [83321.795568] c0 2084 (v.airplayserver) 2350 e5902000 e1500002 > 0a000012 e5903008 e3530000 1a000001 ea000006 e1a03002 > [83321.795572] c0 2084 (v.airplayserver) > LR: 0xc0097320: > [83321.795592] c0 2084 (v.airplayserver) 7320 e5954128 e3540000 > 1affffe1 e59f3090 e2455038 e5933000 e3130080 0a000013 > [83321.795612] c0 2084 (v.airplayserver) 7340 e59734e4 e283101f > e3530000 e203201f b1a03001 e59f106c e1a032c3 e5911000 > [83321.795635] c0 2084 (v.airplayserver) 7360 e7913103 e1a03233 > e3130001 0a000007 e597355c e5933000 e5933018 e3530000 > [83321.795657] c0 2084 (v.airplayserver) 7380 0a000002 e1a00007 > e1a01005 ebfffe2a e1a00005 e8bd80f8 e2860008 eb08abd3 > [83321.795681] c0 2084 (v.airplayserver) 73a0 e3500000 0affffc9 > e2405008 e1a01006 e1a00005 ebffff0d e3500000 c1a05006 > [83321.795702] c0 2084 (v.airplayserver) 73c0 eaffffc2 c0c9b4b4 > c08945bc e92d00f0 e52de004 e8bd4000 e3a02020 e3a03000 > [83321.795724] c0 2084 (v.airplayserver) 73e0 e1530001 01520000 > 3a000004 e59f30ec e0830100 e59000e4 e8bd00f0 e12fff1e > [83321.795746] c0 2084 (v.airplayserver) 7400 e3510000 03500f56 > 8a00002e e1a04000 e1a05001 e3e0601f e3e07000 e3a0c000 > [83321.795751] c0 2084 (v.airplayserver) > SP: 0xce157d98: > [83321.795771] c0 2084 (v.airplayserver) 7d98 ed711dc0 00000000 > 00000000 00000000 c54474c0 00000000 00000000 00000002 > [83321.795795] c0 2084 (v.airplayserver) 7db8 c02c22f0 60060093 > ffffffff ce157e04 ce157f20 c000ead8 00000008 00000000 > [83321.795815] c0 2084 (v.airplayserver) 7dd8 c54478f8 c0097294 > c5447518 00000000 00000000 c54474c0 ce157f20 c0c644c0 > [83321.795838] c0 2084 (v.airplayserver) 7df8 c54474c0 ce157edc > 00000000 ce157e18 c00973a0 c02c22f0 60060093 ffffffff > [83321.795861] c0 2084 (v.airplayserver) 7e18 c0097294 ce1f1d94 > c089595c ce156000 ce1f1ac0 c08880d4 ce157e90 fab25188 > [83321.795881] c0 2084 (v.airplayserver) 7e38 00004bc7 ce157f20 > ce156000 ce157f20 c54449b8 00000000 c08870e8 c0c644c0 > [83321.795903] c0 2084 (v.airplayserver) 7e58 c0c644c0 c0c644c0 > c0c644c0 c0c644c0 00000000 c0087120 c0c61980 00000000 > [83321.795928] c0 2084 (v.airplayserver) 7e78 fab18e38 00004bc7 > ce156000 c0c61980 00000000 c008745c dc2d0e38 00004bc7 > [83321.795930] c0 2084 (v.airplayserver) > FP: 0xce157e5c: > [83321.795951] c0 2084 (v.airplayserver) 7e5c c0c644c0 c0c644c0 > c0c644c0 00000000 c0087120 c0c61980 00000000 fab18e38 > [83321.795973] c0 2084 (v.airplayserver) 7e7c 00004bc7 ce156000 > c0c61980 00000000 c008745c dc2d0e38 00004bc7 ce1f1af8 > [83321.795994] c0 2084 (v.airplayserver) 7e9c a0060013 00000000 > 0000c350 00000000 1e848000 00000000 ce157f20 00000001 > [83321.796018] c0 2084 (v.airplayserver) 7ebc 0000c350 00000000 > 1e848000 00000000 ce157f20 00000001 ce156000 c0db183c > [83321.796039] c0 2084 (v.airplayserver) 7edc c08870e8 0000c350 > 00000001 00000000 1e854350 00000000 00000001 00000000 > [83321.796061] c0 2084 (v.airplayserver) 7efc ce156000 0000c350 > 00000000 ce157f98 c0087b44 0000c350 00000000 1e854350 > [83321.796082] c0 2084 (v.airplayserver) 7f1c 00000000 cc6c5f20 > 00000000 00000000 00000000 fab25188 00004bc7 fab18e38 > [83321.796104] c0 2084 (v.airplayserver) 7f3c 00004bc7 c0086618 > c54449b8 00000001 00000824 c008745c 69612e76 616c7072 > [83321.796108] c0 2084 (v.airplayserver) > R2: 0xc5447878: > [83321.796129] c0 2084 (v.airplayserver) 7878 c5447878 c5447878 > c5447880 c5447880 c5447888 c5447888 c5447890 c5447890 > [83321.796150] c0 2084 (v.airplayserver) 7898 c5447898 c5447898 > c54478a0 c54478a0 c54478a8 c54478a8 c54478b0 c54478b0 > [83321.796171] c0 2084 (v.airplayserver) 78b8 c54478b8 c54478b8 > c54478c0 c54478c0 c54478c8 c54478c8 c54478d0 c54478d0 > [83321.796194] c0 2084 (v.airplayserver) 78d8 c54478d8 c54478d8 > 00000000 00000064 00000064 00000000 00000000 00000000 > [83321.796216] c0 2084 (v.airplayserver) 78f8 c54478f8 c54478f8 > 00000000 00000000 000136df 00000000 389fd980 00000000 > [83321.796237] c0 2084 (v.airplayserver) 7918 dac4dac4 00000000 > c54474c0 c544793c 00200200 c0db0210 ed3192cc c54475a4 > [83321.796258] c0 2084 (v.airplayserver) 7938 04f2cf8e c544793c > c544793c ffffd918 ce1f1ac0 c0ca4800 ee0b1ac0 04f2d06d > [83321.796283] c0 2084 (v.airplayserver) 7958 00000000 00000000 > de023377 00004bc7 de023377 00004bc7 00000000 d98e3c00 > > [83321.796286] c0 2084 (v.airplayserver) > R3: 0xc0097214: > [83321.796306] c0 2084 (v.airplayserver) 7214 1affffb9 e595317c > e3530005 0affffb6 e3550000 0affffb4 e5953124 e5835038 > [83321.796327] c0 2084 (v.airplayserver) 7234 e5955120 e3550000 > 1afffffa eaffffae e1a00004 e58d1004 e3a07001 ebfffa6d > [83321.796350] c0 2084 (v.airplayserver) 7254 e59d1004 eaffff9b > e1a02005 eaffffaf e1a03004 eaffffb5 e1a00004 ebfffa65 > [83321.796371] c0 2084 (v.airplayserver) 7274 eaffffd7 e59131b4 > e3530005 1affffd4 eaffff9d e7f001f2 c0d01f74 c0c9b4b4 > [83321.796395] c0 2084 (v.airplayserver) 7294 e92d40f8 e52de004 > e8bd4000 e1a07000 e5905060 e2804058 e3550000 0a000036 > [83321.796415] c0 2084 (v.airplayserver) 72b4 e594602c e594503c > e3560000 12466008 e1550006 11a05006 0a000031 e5940038 > [83321.796435] c0 2084 (v.airplayserver) 72d4 e3500000 0a000003 > e1a01006 ebffff42 e3500000 d5945038 e5940034 e3500000 > [83321.796458] c0 2084 (v.airplayserver) 72f4 0a000003 e1a01006 > ebffff3b e3500000 d5945034 e1a00004 e1a01005 ebfffebf > [83321.796462] c0 2084 (v.airplayserver) > R4: 0xc5447498: > [83321.796485] c0 2084 (v.airplayserver) 7498 00000000 00000000 > 00000000 00000000 00000000 00000000 00000000 00000000 > [83321.796506] c0 2084 (v.airplayserver) 74b8 00000000 00000000 > 57355734 00000000 00000000 00000000 00000003 00000021 > [83321.796526] c0 2084 (v.airplayserver) 74d8 00000048 04f2cfc4 > 00000000 00000000 00000001 00000000 de021c07 00004bc7 > [83321.796549] c0 2084 (v.airplayserver) 74f8 cc985000 00c0da6a > 29275d16 0000034b 00000000 0315a8b6 115530e2 00000000 > [83321.796571] c0 2084 (v.airplayserver) 7518 0000034b 00000000 > 00000001 00000001 2993334b 00000f7c 267b8ab8 000071c3 > [83321.796595] c0 2084 (v.airplayserver) 7538 267b8ab8 000071c3 > 00000000 00000000 00000000 00000000 00000000 00000000 > [83321.796615] c0 2084 (v.airplayserver) 7558 0000e090 00000000 > 00000000 00000000 00000037 00000000 04bc7de1 00000000 > [83321.796636] c0 2084 (v.airplayserver) 7578 00000000 00000000 > 04bc7de0 00000000 0000001e 00000000 00000037 00000000 > [83321.796641] c0 2084 (v.airplayserver) > R7: 0xc5447440: > [83321.796661] c0 2084 (v.airplayserver) 7440 00000000 ee0be5f0 > ee0be5f0 00000000 00000001 00000000 00000000 00000000 > [83321.796683] c0 2084 (v.airplayserver) 7460 ee0a2980 00000000 > 00000000 00000001 00000000 00000000 00000000 00000000 > [83321.796708] c0 2084 (v.airplayserver) 7480 00000000 00000000 > 00000000 00000000 00000000 00000000 00000000 00000000 > [83321.796729] c0 2084 (v.airplayserver) 74a0 00000000 00000000 > 00000000 00000000 00000000 00000000 00000000 00000000 > [83321.796751] c0 2084 (v.airplayserver) 74c0 57355734 00000000 > 00000000 00000000 00000003 00000021 00000048 04f2cfc4 > [83321.796774] c0 2084 (v.airplayserver) 74e0 00000000 00000000 > 00000001 00000000 de021c07 00004bc7 cc985000 00c0da6a > [83321.796796] c0 2084 (v.airplayserver) 7500 29275d16 0000034b > 00000000 0315a8b6 115530e2 00000000 0000034b 00000000 > [83321.796816] c0 2084 (v.airplayserver) 7520 00000001 00000001 > 2993334b 00000f7c 267b8ab8 000071c3 267b8ab8 000071c3 > [83321.796820] c0 2084 (v.airplayserver) > R8: 0xce157ea0: > [83321.796841] c0 2084 (v.airplayserver) 7ea0 00000000 0000c350 > 00000000 1e848000 00000000 ce157f20 00000001 0000c350 > [83321.796862] c0 2084 (v.airplayserver) 7ec0 00000000 1e848000 > 00000000 ce157f20 00000001 ce156000 c0db183c c08870e8 > [83321.796882] c0 2084 (v.airplayserver) 7ee0 0000c350 00000001 > 00000000 1e854350 00000000 00000001 00000000 ce156000 > [83321.796905] c0 2084 (v.airplayserver) 7f00 0000c350 00000000 > ce157f98 c0087b44 0000c350 00000000 1e854350 00000000 > [83321.796927] c0 2084 (v.airplayserver) 7f20 cc6c5f20 00000000 > 00000000 00000000 fab25188 00004bc7 fab18e38 00004bc7 > [83321.796948] c0 2084 (v.airplayserver) 7f40 c0086618 c54449b8 > 00000001 00000824 c008745c 69612e76 616c7072 72657379 > [83321.796971] c0 2084 (v.airplayserver) 7f60 00726576 00000000 > ce1f1ac0 ce156000 047e3000 00000000 00000150 1dcd64ff > [83321.796992] c0 2084 (v.airplayserver) 7f80 000000a2 c000f124 > ce156000 00000000 77d80ca4 c0087c60 00000000 1e848000 > [83321.796994] c0 2084 (v.airplayserver) > R9: 0xc0c64440: > [83321.797018] c0 2084 (v.airplayserver) 4440 e7fddef0 e7fddef0 > e7fddef0 e7fddef0 e7fddef0 e7fddef0 e7fddef0 e7fddef0 > [83321.797038] c0 2084 (v.airplayserver) 4460 e7fddef0 e7fddef0 > e7fddef0 e7fddef0 e7fddef0 e7fddef0 e7fddef0 e7fddef0 > [83321.797062] c0 2084 (v.airplayserver) 4480 e7fddef0 e7fddef0 > e7fddef0 e7fddef0 e7fddef0 e7fddef0 e7fddef0 e7fddef0 > [83321.797084] c0 2084 (v.airplayserver) 44a0 e7fddef0 e7fddef0 > e7fddef0 e7fddef0 e7fddef0 e7fddef0 e7fddef0 e7fddef0 > [83321.797108] c0 2084 (v.airplayserver) 44c0 e7fddef0 e7fddef0 > e7fddef0 e7fddef0 e7fddef0 e7fddef0 e7fddef0 e7fddef0 > [83321.797128] c0 2084 (v.airplayserver) 44e0 e7fddef0 e7fddef0 > e7fddef0 e7fddef0 e7fddef0 e7fddef0 e7fddef0 e7fddef0 > [83321.797150] c0 2084 (v.airplayserver) 4500 e7fddef0 e7fddef0 > e7fddef0 e7fddef0 e7fddef0 e7fddef0 e7fddef0 e7fddef0 > [83321.797173] c0 2084 (v.airplayserver) 4520 e7fddef0 e7fddef0 > e7fddef0 e7fddef0 e7fddef0 e7fddef0 e7fddef0 e7fddef0 > [83321.797178] c0 2084 (v.airplayserver) > R10: 0xc5447440: > [83321.797200] c0 2084 (v.airplayserver) 7440 00000000 ee0be5f0 > ee0be5f0 00000000 00000001 00000000 00000000 00000000 > [83321.797221] c0 2084 (v.airplayserver) 7460 ee0a2980 00000000 > 00000000 00000001 00000000 00000000 00000000 00000000 > [83321.797243] c0 2084 (v.airplayserver) 7480 00000000 00000000 > 00000000 00000000 00000000 00000000 00000000 00000000 > [83321.797265] c0 2084 (v.airplayserver) 74a0 00000000 00000000 > 00000000 00000000 00000000 00000000 00000000 00000000 > [83321.797286] c0 2084 (v.airplayserver) 74c0 57355734 00000000 > 00000000 00000000 00000003 00000021 00000048 04f2cfc4 > [83321.797310] c0 2084 (v.airplayserver) 74e0 00000000 00000000 > 00000001 00000000 de021c07 00004bc7 cc985000 00c0da6a > [83321.797333] c0 2084 (v.airplayserver) 7500 29275d16 0000034b > 00000000 0315a8b6 115530e2 00000000 0000034b 00000000 > [83321.797354] c0 2084 (v.airplayserver) 7520 00000001 00000001 > 2993334b 00000f7c 267b8ab8 000071c3 267b8ab8 000071c3 > [83321.797360] c0 2084 (v.airplayserver) Process v.airplayserver (pid: > 2084, stack limit = 0xce156238) > [83321.797365] c0 2084 (v.airplayserver) Stack: (0xce157e18 to 0xce158000) > [83321.797370] c0 2084 (v.airplayserver) 7e00: c0097294 ce1f1d94 > [83321.797375] c0 2084 (v.airplayserver) 7e20: c089595c ce156000 > ce1f1ac0 c08880d4 ce157e90 fab25188 00004bc7 ce157f20 > [83321.797380] c0 2084 (v.airplayserver) 7e40: ce156000 ce157f20 > c54449b8 00000000 c08870e8 c0c644c0 c0c644c0 c0c644c0 > [83321.797385] c0 2084 (v.airplayserver) 7e60: c0c644c0 c0c644c0 > 00000000 c0087120 c0c61980 00000000 fab18e38 00004bc7 > [83321.797390] c0 2084 (v.airplayserver) 7e80: ce156000 c0c61980 > 00000000 c008745c dc2d0e38 00004bc7 ce1f1af8 a0060013 > [83321.797395] c0 2084 (v.airplayserver) 7ea0: 00000000 0000c350 > 00000000 1e848000 00000000 ce157f20 00000001 0000c350 > [83321.797399] c0 2084 (v.airplayserver) 7ec0: 00000000 1e848000 > 00000000 ce157f20 00000001 ce156000 c0db183c c08870e8 > [83321.797403] c0 2084 (v.airplayserver) 7ee0: 0000c350 00000001 > 00000000 1e854350 00000000 00000001 00000000 ce156000 > [83321.797408] c0 2084 (v.airplayserver) 7f00: 0000c350 00000000 > ce157f98 c0087b44 0000c350 00000000 1e854350 00000000 > [83321.797412] c0 2084 (v.airplayserver) 7f20: cc6c5f20 00000000 > 00000000 00000000 fab25188 00004bc7 fab18e38 00004bc7 > [83321.797417] c0 2084 (v.airplayserver) 7f40: c0086618 c54449b8 > 00000001 00000824 c008745c 69612e76 616c7072 72657379 > [83321.797421] c0 2084 (v.airplayserver) 7f60: 00726576 00000000 > ce1f1ac0 ce156000 047e3000 00000000 00000150 1dcd64ff > [83321.797426] c0 2084 (v.airplayserver) 7f80: 000000a2 c000f124 > ce156000 00000000 77d80ca4 c0087c60 00000000 1e848000 > [83321.797431] c0 2084 (v.airplayserver) 7fa0: 437b1bac c000ef80 > 437b1bac 00000150 77d80c70 00000000 00000001 00000128 > [83321.797436] c0 2084 (v.airplayserver) 7fc0: 437b1bac 00000150 > 1dcd64ff 000000a2 77544008 1e848000 437b1ba8 77d80ca4 > [83321.797441] c0 2084 (v.airplayserver) 7fe0: 0000002a 77d80c68 > 4157025c 4009fe44 20060010 77d80c70 ff080001 ff080001 > [83321.797457] c0 2084 (v.airplayserver) [] > (rb_next+0x0/0x60) from [] (pick_next_task_fair+0x10c/0x138) > [83321.797478] c0 2084 (v.airplayserver) [] > (pick_next_task_fair+0x10c/0x138) from [] > (__schedule+0x678/0x7e8) > [83321.797491] c0 2084 (v.airplayserver) [] > (__schedule+0x678/0x7e8) from [] (do_nanosleep+0xb4/0x134) > [83321.797502] c0 2084 (v.airplayserver) [] > (do_nanosleep+0xb4/0x134) from [] > (hrtimer_nanosleep+0x98/0x110) > [83321.797509] c0 2084 (v.airplayserver) [] > (hrtimer_nanosleep+0x98/0x110) from [] > (SyS_nanosleep+0xa4/0xb0) > [83321.797523] c0 2084 (v.airplayserver) [] > (SyS_nanosleep+0xa4/0xb0) from [] > (ret_fast_syscall+0x0/0x30) > [83321.797531] c0 2084 (v.airplayserver) Code: 15821000 e8900007 > e8830007 e12fff1e (e5902000) -- 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/