Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754068Ab0LHD2U (ORCPT ); Tue, 7 Dec 2010 22:28:20 -0500 Received: from ipmail07.adl2.internode.on.net ([150.101.137.131]:52454 "EHLO ipmail07.adl2.internode.on.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753467Ab0LHD2S (ORCPT ); Tue, 7 Dec 2010 22:28:18 -0500 X-IronPort-Anti-Spam-Filtered: true X-IronPort-Anti-Spam-Result: AvsEAJeJ/kx5Lclt/2dsb2JhbACjSXLBHoVJBA Date: Wed, 8 Dec 2010 14:28:13 +1100 From: Nick Piggin To: Nick Piggin Cc: Dave Chinner , Nick Piggin , linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, Peter Zijlstra Subject: Re: [PATCH 00/46] rcu-walk and dcache scaling Message-ID: <20101208032813.GA6812@amd> References: <20101207112555.GE16103@dastard> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: User-Agent: Mutt/1.5.20 (2009-06-14) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 8981 Lines: 145 On Wed, Dec 08, 2010 at 02:24:23AM +1100, Nick Piggin wrote: > On Tue, Dec 7, 2010 at 10:25 PM, Dave Chinner wrote: > > [ 5954.061633] BUG: sleeping function called from invalid context at arch/x86/mm/fault.c:1081 > > [ 5954.062466] in_atomic(): 0, irqs_disabled(): 1, pid: 2927, name: rm > > [ 5954.063122] 3 locks held by rm/2927: > > [ 5954.063476] ?#0: ?(&sb->s_type->i_mutex_key#12/1){+.+.+.}, at: [] do_rmdir+0x81/0x130 > > [ 5954.064014] ?#1: ?(&sb->s_type->i_mutex_key#12){+.+.+.}, at: [] vfs_rmdir+0x58/0xe0 > > [ 5954.064014] ?#2: ?(rcu_read_lock){.+.+..}, at: [] shrink_dentry_list+0x0/0x430 > > [ 5954.064014] irq event stamp: 1484376719 > > [ 5954.064014] hardirqs last ?enabled at (1484376719): [] __call_rcu+0xd7/0x1a0 > > [ 5954.064014] hardirqs last disabled at (1484376718): [] __call_rcu+0x4a/0x1a0 > > [ 5954.064014] softirqs last ?enabled at (1484376586): [] __do_softirq+0x161/0x270 > > [ 5954.064014] softirqs last disabled at (1484376581): [] call_softirq+0x1c/0x50 > > [ 5954.064014] Pid: 2927, comm: rm Not tainted 2.6.37-rc4-dgc+ #794 > > [ 5954.064014] Call Trace: > > [ 5954.064014] ?[] ? print_irqtrace_events+0xd0/0xe0 > > [ 5954.064014] ?[] __might_sleep+0xf5/0x130 > > [ 5954.064014] ?[] do_page_fault+0x103/0x4f0 > > [ 5954.064014] ?[] ? pvclock_clocksource_read+0x58/0xd0 > > [ 5954.064014] ?[] ? pvclock_clocksource_read+0x58/0xd0 > > [ 5954.064014] ?[] ? pvclock_clocksource_read+0x58/0xd0 > > [ 5954.064014] ?[] ? trace_hardirqs_off_thunk+0x3a/0x3c > > [ 5954.064014] ?[] ? usage_match+0x0/0x20 > > [ 5954.064014] ?[] page_fault+0x25/0x30 > > [ 5954.064014] ?[] ? usage_match+0x0/0x20 > > [ 5954.064014] ?[] ? __bfs+0xc8/0x260 > > [ 5954.064014] ?[] ? __bfs+0x23/0x260 > > [ 5954.064014] ?[] find_usage_backwards+0x42/0x80 > > [ 5954.064014] ?[] check_usage_backwards+0x64/0xf0 > > [ 5954.064014] ?[] ? save_stack_trace+0x2f/0x50 > > [ 5954.064014] ?[] ? check_usage_backwards+0x0/0xf0 > > [ 5954.064014] ?[] mark_lock+0x1a9/0x440 > > [ 5954.064014] ?[] __lock_acquire+0x5a9/0x14b0 > > [ 5954.064014] ?[] ? __lock_acquire+0x336/0x14b0 > > [ 5954.064014] ?[] ? pvclock_clocksource_read+0x58/0xd0 > > [ 5954.064014] ?[] lock_acquire+0xb4/0x140 > > [ 5954.064014] ?[] ? shrink_dentry_list+0x5c/0x430 > > [ 5954.064014] ?[] _raw_spin_lock+0x36/0x70 > > [ 5954.064014] ?[] ? shrink_dentry_list+0x5c/0x430 > > [ 5954.064014] ?[] shrink_dentry_list+0x5c/0x430 > > [ 5954.064014] ?[] ? shrink_dentry_list+0x0/0x430 > > [ 5954.064014] ?[] ? do_raw_spin_unlock+0x5e/0xb0 > > [ 5954.064014] ?[] __shrink_dcache_sb+0x13d/0x1c0 > > [ 5954.064014] ?[] shrink_dcache_parent+0x32f/0x390 > > [ 5954.064014] ?[] dentry_unhash+0x3d/0x70 > > [ 5954.064014] ?[] vfs_rmdir+0x60/0xe0 > > [ 5954.064014] ?[] do_rmdir+0x113/0x130 > > [ 5954.064014] ?[] ? sysret_check+0x2e/0x69 > > [ 5954.064014] ?[] ? trace_hardirqs_on_thunk+0x3a/0x3f > > [ 5954.064014] ?[] sys_unlinkat+0x35/0x40 > > [ 5954.064014] ?[] system_call_fastpath+0x16/0x1b > > Seems that lockdep exploded. > > > [ 5954.092916] BUG: unable to handle kernel NULL pointer dereference at ? ? ? ? ? (null) > > [ 5954.093806] IP: [] __bfs+0xc8/0x260 > > [ 5954.094331] PGD 1084e5067 PUD 102368067 PMD 0 > > [ 5954.094830] Oops: 0000 [#1] SMP > > [ 5954.095194] last sysfs file: /sys/devices/system/cpu/online > > [ 5954.095760] CPU 6 > > [ 5954.095954] Modules linked in: > > [ 5954.096319] > > [ 5954.096483] Pid: 2927, comm: rm Not tainted 2.6.37-rc4-dgc+ #794 /Bochs > > [ 5954.096665] RIP: 0010:[] ?[] __bfs+0xc8/0x260 > > [ 5954.096665] RSP: 0018:ffff8801175539a8 ?EFLAGS: 00010046 > > [ 5954.096665] RAX: ffffffff8267d980 RBX: ffffffff8267d980 RCX: ffff880117553a48 > > [ 5954.096665] RDX: ffff8801175539d0 RSI: 0000000000000000 RDI: ffff880117553a48 > > [ 5954.096665] RBP: ffff880117553a08 R08: 0000000000000000 R09: 0000000000000000 > > [ 5954.096665] R10: 0000000000000000 R11: 0000000000000001 R12: 0000000000000000 > > [ 5954.096665] R13: ffffffff810b8e20 R14: ffff880117553a90 R15: 0000000000000000 > > [ 5954.096665] FS: ?00007f4594cf3700(0000) GS:ffff8800dfa00000(0000) knlGS:0000000000000000 > > [ 5954.096665] CS: ?0010 DS: 0000 ES: 0000 CR0: 000000008005003b > > [ 5954.096665] CR2: 00007f2f21e89c60 CR3: 0000000110b0f000 CR4: 00000000000006e0 > > [ 5954.096665] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 > > [ 5954.096665] DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400 > > [ 5954.096665] Process rm (pid: 2927, threadinfo ffff880117552000, task ffff88010ff10b00) > > [ 5954.096665] Stack: > > [ 5954.096665] ?ffffffff8267d868 00007fffa02d1428 ffff8800ffffffff ffff880100000000 > > [ 5954.096665] ?000000000000b720 ffff880117553a48 ffffffff8267d868 ffff880117553a48 > > [ 5954.096665] ?0000000000000000 ffff88010ff10b00 0000000000000000 ffffffff81dacba0 > > [ 5954.096665] Call Trace: > > [ 5954.096665] ?[] find_usage_backwards+0x42/0x80 > > [ 5954.096665] ?[] check_usage_backwards+0x64/0xf0 > > [ 5954.096665] ?[] ? save_stack_trace+0x2f/0x50 > > [ 5954.096665] ?[] ? check_usage_backwards+0x0/0xf0 > > [ 5954.096665] ?[] mark_lock+0x1a9/0x440 > > [ 5954.096665] ?[] __lock_acquire+0x5a9/0x14b0 > > [ 5954.096665] ?[] ? __lock_acquire+0x336/0x14b0 > > [ 5954.096665] ?[] ? pvclock_clocksource_read+0x58/0xd0 > > [ 5954.096665] ?[] lock_acquire+0xb4/0x140 > > [ 5954.096665] ?[] ? shrink_dentry_list+0x5c/0x430 > > [ 5954.096665] ?[] _raw_spin_lock+0x36/0x70 > > [ 5954.096665] ?[] ? shrink_dentry_list+0x5c/0x430 > > [ 5954.096665] ?[] shrink_dentry_list+0x5c/0x430 > > [ 5954.096665] ?[] ? shrink_dentry_list+0x0/0x430 > > [ 5954.096665] ?[] ? do_raw_spin_unlock+0x5e/0xb0 > > [ 5954.096665] ?[] __shrink_dcache_sb+0x13d/0x1c0 > > [ 5954.096665] ?[] shrink_dcache_parent+0x32f/0x390 > > [ 5954.096665] ?[] dentry_unhash+0x3d/0x70 > > [ 5954.096665] ?[] vfs_rmdir+0x60/0xe0 > > [ 5954.096665] ?[] do_rmdir+0x113/0x130 > > [ 5954.096665] ?[] ? sysret_check+0x2e/0x69 > > [ 5954.096665] ?[] ? trace_hardirqs_on_thunk+0x3a/0x3f > > [ 5954.096665] ?[] sys_unlinkat+0x35/0x40 > > [ 5954.096665] ?[] system_call_fastpath+0x16/0x1b > > [ 5954.096665] Code: 0a 89 05 dc 0f a8 01 48 8b 41 10 48 85 c0 0f 84 1f 01 00 00 48 8d 98 70 01 00 00 48 05 80 01 00 00 45 85 c0 48 0f 44 d8 4c 8b 3b <49> 8b 07 49 39 > > [ 5954.096665] RIP ?[] __bfs+0xc8/0x260 > > [ 5954.096665] ?RSP > > [ 5954.096665] CR2: 0000000000000000 > > [ 5954.127991] ---[ end trace 85a6727c2d4e3d90 ]--- > > So vfs-scale-working branch may not be entirely in the clear, seeing Ah, may have been a stupid little bug. The list entry check was being done and then the pointer reloaded to be used. What does the asm for shrink_dentry_list look like (before this patch)? Thanks, Nick Index: linux-2.6/fs/dcache.c =================================================================== --- linux-2.6.orig/fs/dcache.c 2010-12-08 12:41:35.000000000 +1100 +++ linux-2.6/fs/dcache.c 2010-12-08 14:23:46.000000000 +1100 @@ -657,10 +657,10 @@ static void shrink_dentry_list(struct li struct dentry *dentry; rcu_read_lock(); - while (!list_empty(list)) { - dentry = list_entry(list->prev, struct dentry, d_lru); - - /* Don't need RCU dereference because we recheck under lock */ + for (;;) { + dentry = list_entry_rcu(list->prev, struct dentry, d_lru); + if (&dentry->d_lru == list) + break; spin_lock(&dentry->d_lock); if (dentry != list_entry(list->prev, struct dentry, d_lru)) { spin_unlock(&dentry->d_lock); -- 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/