Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754761Ab1DROVq (ORCPT ); Mon, 18 Apr 2011 10:21:46 -0400 Received: from mailout-de.gmx.net ([213.165.64.23]:60329 "HELO mailout-de.gmx.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S1754078Ab1DROVk (ORCPT ); Mon, 18 Apr 2011 10:21:40 -0400 X-Authenticated: #14349625 X-Provags-ID: V01U2FsdGVkX1+TGE0jj/mTtMD7o8MX0MqsszUo2nCxm7QKtPSzFp IaIp5otAXqbaS0 Subject: Re: query: [PATCH 2/2] cgroup: Remove call to synchronize_rcu in cgroup_attach_task From: Mike Galbraith To: Paul Menage Cc: Li Zefan , LKML , Colin Cross , Peter Zijlstra , Ingo Molnar In-Reply-To: References: <1302170153.12304.31.camel@marge.simson.net> <4DA50430.8020701@cn.fujitsu.com> <1302664313.7407.29.camel@marge.simson.net> Content-Type: text/plain; charset="UTF-8" Date: Mon, 18 Apr 2011 16:21:34 +0200 Message-ID: <1303136494.7542.20.camel@marge.simson.net> Mime-Version: 1.0 X-Mailer: Evolution 2.32.1 Content-Transfer-Encoding: 7bit X-Y-GMX-Trusted: 0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4744 Lines: 77 On Wed, 2011-04-13 at 15:16 +0200, Paul Menage wrote: > Also, I'd be concerned that subsystems might get confused by the fact > that a new group called 'foo' could be created before the old 'foo' > has been cleaned up? Decided to try beating on that without my hack. Seems these patches... patches/cgroup-Set-CGRP_RELEASABLE-when-adding-to-a-group patches/cgroup-Remove-call-to-synchronize_rcu-in-cgroup_attach_task ...either introduced a bug, or made an existing one easier to hit. With only those two applied, and several tasks doing - create, attach, detach, fork off a rmdir - all for the same cgroup, box griped. With my hack on top, I'd either see rcu workers explode, or list corruption in cgroup_attach_task(), depending on phase-of-moon. (hohum, maybe it'll turn out to be a defenseless _baby_ dragon..) v2.6.39-rc2 [ 5009.808292] general protection fault: 0000 [#1] SMP [ 5009.812007] last sysfs file: /sys/devices/system/cpu/cpu3/cache/index2/shared_cpu_map [ 5009.812007] CPU 2 [ 5009.812007] Modules linked in: snd_pcm_oss snd_mixer_oss snd_seq snd_seq_device edd nfsd lockd nfs_acl auth_rpcgss sunrpc parport_pc parport bridge stp cpufreq_conservative cpufreq_ondemand microcode cpufreq_userspace cpufreq_powersave acpi_cpufreq mperf nls_iso8859_1 nls_cp437 vfat fat fuse ext3 jbd dm_mod snd_hda_codec_realtek snd_hda_intel snd_hda_codec snd_hwdep snd_pcm sr_mod sg usb_storage usbmouse cdrom snd_timer usbhid hid firewire_ohci firewire_core snd usb_libusual i2c_i801 soundcore snd_page_alloc e1000e crc_itu_t button ext4 mbcache jbd2 crc16 uhci_hcd ehci_hcd sd_mod rtc_cmos usbcore rtc_core rtc_lib ahci libahci libata scsi_mod fan processor thermal [ 5009.812007] [ 5009.812007] Pid: 21021, comm: rmdir Not tainted 2.6.39-smpx #1906 MEDIONPC MS-7502/MS-7502 [ 5009.812007] RIP: 0010:[] [] cgroup_css_sets_empty+0x25/0x50 [ 5009.812007] RSP: 0018:ffff88017dfe5dd8 EFLAGS: 00010246 [ 5009.812007] RAX: dead000000100100 RBX: 0000000000000000 RCX: ffff880228c8ce50 [ 5009.812007] RDX: dead000000100100 RSI: ffff88022db9b900 RDI: ffff880228c8cc00 [ 5009.812007] RBP: ffff88017dfe5dd8 R08: 0000000000000005 R09: ffff88022db9b93c [ 5009.812007] R10: ffff88017dfe5d18 R11: ffff88017dfe5c84 R12: ffff880228c8cc00 [ 5009.812007] R13: ffff88017dfe5df8 R14: ffff880228c8cc20 R15: ffff8802161cd240 [ 5009.812007] FS: 00007fefea0a1700(0000) GS:ffff88022fd00000(0000) knlGS:0000000000000000 [ 5009.812007] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 5009.955702] CR2: 00007fefe9c1acb0 CR3: 000000019107c000 CR4: 00000000000006e0 [ 5009.955702] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 [ 5009.955702] DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400 [ 5009.955702] Process rmdir (pid: 21021, threadinfo ffff88017dfe4000, task ffff8802161cd240) [ 5009.955702] Stack: [ 5009.955702] ffff88017dfe5e58 ffffffff8107a514 ffff88022db9b9a0 ffff88022db9badc [ 5009.955702] 0000000000000000 ffff8802161cd240 ffffffff81057ee0 ffff88017dfe5e10 [ 5009.955702] ffff88017dfe5e10 0000000000000000 0000000000000001 ffff88022db9b900 [ 5009.955702] Call Trace: [ 5009.955702] [] cgroup_rmdir+0x64/0x510 [ 5009.955702] [] ? wake_up_bit+0x40/0x40 [ 5009.955702] [] vfs_rmdir+0x96/0xe0 [ 5009.955702] [] do_rmdir+0x103/0x120 [ 5009.955702] [] sys_rmdir+0x11/0x20 [ 5009.955702] [] system_call_fastpath+0x16/0x1b [ 5009.955702] Code: 84 00 00 00 00 00 55 48 8b 87 50 02 00 00 48 89 e5 48 8d 8f 50 02 00 00 eb 11 0f 1f 40 00 48 8b 40 28 8b 00 85 c0 7f 1e 48 89 d0 [ 5009.955702] 8b 10 48 39 c8 0f 18 0a 75 e8 b8 01 00 00 00 c9 c3 66 0f 1f [ 5009.955702] RIP [] cgroup_css_sets_empty+0x25/0x50 [ 5009.955702] RSP [ 5010.075058] hpet1: lost 12 rtc interrupts [ 5010.079153] ---[ end trace df95d1af02295a25 ]--- (gdb) list *cgroup_css_sets_empty+0x25 0xffffffff81079df5 is in cgroup_css_sets_empty (kernel/cgroup.c:3589). 3584 * Must be called with css_set_lock held */ 3585 static int cgroup_css_sets_empty(struct cgroup *cgrp) 3586 { 3587 struct cg_cgroup_link *link; 3588 3589 list_for_each_entry(link, &cgrp->css_sets, cgrp_link_list) { 3590 struct css_set *cg = link->cg; 3591 if (atomic_read(&cg->refcount) > 0) 3592 return 0; 3593 } (gdb) -- 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/