Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756741AbXKUEJo (ORCPT ); Tue, 20 Nov 2007 23:09:44 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752656AbXKUEJf (ORCPT ); Tue, 20 Nov 2007 23:09:35 -0500 Received: from smtp2.linux-foundation.org ([207.189.120.14]:58892 "EHLO smtp2.linux-foundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752386AbXKUEJe (ORCPT ); Tue, 20 Nov 2007 23:09:34 -0500 Date: Tue, 20 Nov 2007 20:08:42 -0800 From: Andrew Morton To: Alexey Dobriyan Cc: linux-kernel@vger.kernel.org, viro@zeniv.linux.org.uk, devel@openvz.org, "Eric W. Biederman" , Andy Whitcroft Subject: Re: [PATCH 3/4] proc: simplify remove_proc_entry() wrt locking Message-Id: <20071120200842.a3ad33b5.akpm@linux-foundation.org> In-Reply-To: <20071116151015.GE19517@localhost.sw.ru> References: <20071116151015.GE19517@localhost.sw.ru> X-Mailer: Sylpheed 2.4.1 (GTK+ 2.8.17; x86_64-unknown-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4121 Lines: 81 On Fri, 16 Nov 2007 18:10:15 +0300 Alexey Dobriyan wrote: > We can take proc_subdir_lock for duration of list searching and removing > from lists only. It can't hurt -- we can gather any amount of looked up > PDEs right after proc_subdir_lock droppage in proc_lookup() anyway. > Current code should already deal with this correctly. > > Also this should make code more undestandable: > * original looks like a loop, however, it's a loop with unconditional > trailing "break;" -- not loop at all. > * more explicit statement that proc_subdir_lock protects only ->subdir lists. oopses the Vaio. [ 12.595145] BUG: unable to handle kernel NULL pointer dereference at virtual address 00000030 [ 12.598487] printing eip: c01a607f *pde = 00000000 [ 12.601795] Oops: 0000 [#1] PREEMPT [ 12.605101] last sysfs file: [ 12.608432] Modules linked in: [ 12.611727] [ 12.615000] Pid: 1, comm: swapper Not tainted (2.6.24-rc3-mm1 #4) [ 12.618345] EIP: 0060:[] EFLAGS: 00010206 CPU: 0 [ 12.621713] EIP is at remove_proc_entry+0x69/0x16c [ 12.625071] EAX: 00000000 EBX: f726d940 ECX: f726d9bd EDX: 00000000 [ 12.628445] ESI: 00000030 EDI: f726d940 EBP: f7841e3c ESP: f7841dcc [ 12.631747] DS: 007b ES: 007b FS: 0000 GS: 0000 SS: 0068 [ 12.635052] Process swapper (pid: 1, ti=F7840000 task=F783ED30 task.ti=F7840000) [ 12.635181] Stack: 00000005 f726d9c0 c042747c f7841df0 c0131992 00000282 f7841e1c 00000005 [ 12.638669] 00000000 00000046 00000174 00000000 c0138012 00000000 00000000 00000000 [ 12.642173] f783f2e0 f783ed30 00000000 f783ed30 c0320d27 00000010 f7841e34 c013a1e4 [ 12.645623] Call Trace: [ 12.652432] [] show_trace_log_lvl+0x12/0x25 [ 12.655938] [] show_stack_log_lvl+0x8c/0x9e [ 12.659333] [] show_registers+0x8a/0x1c0 [ 12.662755] [] die+0xee/0x1c4 [ 12.666101] [] do_page_fault+0x405/0x4e1 [ 12.669427] [] error_code+0x6a/0x70 [ 12.672700] [] unregister_handler_proc+0x1b/0x1d [ 12.675974] [] free_irq+0xb3/0xdc [ 12.679227] [] yenta_probe_cb_irq+0xc9/0xd6 [ 12.682482] [] ti12xx_override+0x12b/0x4c5 [ 12.685782] [] yenta_probe+0x2b1/0x55d [ 12.689042] [] pci_device_probe+0x39/0x5b [ 12.692276] [] driver_probe_device+0xd1/0x147 [ 12.695492] [] __driver_attach+0x6a/0xa1 [ 12.698666] [] bus_for_each_dev+0x37/0x5c [ 12.701783] [] driver_attach+0x14/0x16 [ 12.704891] [] bus_add_driver+0x7a/0x191 [ 12.708015] [] driver_register+0x57/0x5c [ 12.711095] [] __pci_register_driver+0x56/0x83 [ 12.714170] [] yenta_socket_init+0x14/0x16 [ 12.717195] [] kernel_init+0xc5/0x20f [ 12.720120] [] kernel_thread_helper+0x7/0x10 [ 12.723041] ======================= [ 12.725918] INFO: lockdep is turned off. [ 12.728813] Code: 75 94 83 c6 38 eb 24 8b 55 f0 89 d9 8b 45 90 e8 ab fe ff ff 85 c0 74 0e 8b 43 30 89 df 89 06 c7 43 30 00 00 00 00 8b 36 83 c6 30 <8b> 1e 85 db 75 d6 b8 e0 2b 43 c0 e8 ab ab 17 00 85 ff 0f 84 e3 [ 12.735473] EIP: [] remove_proc_entry+0x69/0x16c SS:ESP 0068:f7841dcc (gdb) l *0xc01a4fdf 0xc01a4fdf is in remove_proc_entry (fs/proc/generic.c:698). warning: Source file is more recent than executable. 693 if (!parent && xlate_proc_name(name, &parent, &fn) != 0) 694 return; 695 len = strlen(fn); 696 697 spin_lock(&proc_subdir_lock); 698 for (p = &parent->subdir; *p; p=&(*p)->next ) { 699 if (!proc_match(len, fn, *p)) 700 continue; 701 de = *p; 702 *p = de->next; iirc this is what Andy was hitting. - 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/