From patchwork Fri Oct 10 14:23:42 2014 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Jan Kara X-Patchwork-Id: 398610 Return-Path: X-Original-To: patchwork-incoming@ozlabs.org Delivered-To: patchwork-incoming@ozlabs.org Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by ozlabs.org (Postfix) with ESMTP id BFC981400B6 for ; Sat, 11 Oct 2014 01:25:05 +1100 (EST) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755296AbaJJOZD (ORCPT ); Fri, 10 Oct 2014 10:25:03 -0400 Received: from cantor2.suse.de ([195.135.220.15]:37277 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755065AbaJJOYV (ORCPT ); Fri, 10 Oct 2014 10:24:21 -0400 Received: from relay2.suse.de (charybdis-ext.suse.de [195.135.220.254]) by mx2.suse.de (Postfix) with ESMTP id 73AC6ADF8; Fri, 10 Oct 2014 14:24:04 +0000 (UTC) Received: by quack.suse.cz (Postfix, from userid 1000) id 0992D82059; Fri, 10 Oct 2014 16:24:01 +0200 (CEST) From: Jan Kara To: linux-fsdevel@vger.kernel.org Cc: linux-ext4@vger.kernel.org, Dave Chinner , xfs@oss.sgi.com, cluster-devel@redhat.com, Steven Whitehouse , Mark Fasheh , Joel Becker , ocfs2-devel@oss.oracle.com, reiserfs-devel@vger.kernel.org, Jeff Mahoney , Dave Kleikamp , jfs-discussion@lists.sourceforge.net, tytso@mit.edu, viro@zeniv.linux.org.uk, Jan Kara Subject: [PATCH] x86: Fixup lockdep complaint caused by io apic code Date: Fri, 10 Oct 2014 16:23:42 +0200 Message-Id: <1412951028-4085-38-git-send-email-jack@suse.cz> X-Mailer: git-send-email 1.8.1.4 In-Reply-To: <1412951028-4085-1-git-send-email-jack@suse.cz> References: <1412951028-4085-1-git-send-email-jack@suse.cz> Sender: linux-ext4-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-ext4@vger.kernel.org 0day kernel testing guys have reported following lockdep complaint: ====================================================== [ INFO: possible circular locking dependency detected ] 3.15.0-rc5-00567-gbafe980 #1 Not tainted ------------------------------------------------------- swapper/1 is trying to acquire lock: (&irq_desc_lock_class){-.-...}, at: [<8107dc8c>] __irq_get_desc_lock+0x3c/0x70 but task is already holding lock: (&port_lock_key){......}, at: [<815f5b27>] serial8250_startup+0x337/0x720 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #2 (&port_lock_key){......}: lock when printing to serial console> [<810750e5>] lock_acquire+0x85/0x190 [<81baed9d>] _raw_spin_lock_irqsave+0x4d/0x60 [<8106eb1c>] down_trylock+0xc/0x30 [<8107b795>] console_trylock+0x15/0xb0 [<8107be8f>] vprintk_emit+0x14f/0x4d0 [<81b969b9>] printk+0x38/0x3a [<82137f78>] print_ICs+0x5b/0x3e7 [<8212bb41>] do_one_initcall+0x8b/0x128 [<8212bd7d>] kernel_init_freeable+0x19f/0x236 [<81b9238b>] kernel_init+0xb/0xd0 [<81bb0080>] ret_from_kernel_thread+0x20/0x30 -> #1 (i8259A_lock){-.....}: [<810750e5>] lock_acquire+0x85/0x190 [<81baed9d>] _raw_spin_lock_irqsave+0x4d/0x60 [<81005af1>] unmask_8259A_irq+0x11/0x60 [<81005b4b>] enable_8259A_irq+0xb/0x10 [<8107fffb>] irq_enable+0x2b/0x40 [<8108005d>] irq_startup+0x4d/0x60 [<8107f2bc>] __setup_irq+0x39c/0x460 [<8107f433>] setup_irq+0x33/0x80 [<8212db15>] setup_default_timer_irq+0xf/0x11 [<8212db2d>] hpet_time_init+0x16/0x18 [<8212daff>] x86_late_time_init+0x9/0x10 [<8212ba3d>] start_kernel+0x331/0x3aa [<8212b380>] i386_start_kernel+0x12e/0x131 -> #0 (&irq_desc_lock_class){-.-...}: [<810743c2>] __lock_acquire+0x19c2/0x1b20 [<810750e5>] lock_acquire+0x85/0x190 [<81baed9d>] _raw_spin_lock_irqsave+0x4d/0x60 [<8107dc8c>] __irq_get_desc_lock+0x3c/0x70 [<8107eb1e>] __disable_irq_nosync+0x1e/0x50 [<8107eb58>] disable_irq_nosync+0x8/0x10 [<815f5c78>] serial8250_startup+0x488/0x720 [<815f205e>] uart_startup.part.4+0x6e/0x1e0 [<815f2a40>] uart_open+0xe0/0x140 [<815e4b51>] tty_open+0x141/0x510 [<81118bc0>] chrdev_open+0x60/0x140 [<8111372c>] do_dentry_open+0x14c/0x230 [<8111459e>] finish_open+0x2e/0x40 [<8112132a>] do_last+0x4aa/0xd30 [<81121c5a>] path_openat+0xaa/0x610 [<811221ec>] do_filp_open+0x2c/0x70 [<81114a81>] do_sys_open+0x111/0x210 [<81114b9d>] SyS_open+0x1d/0x20 [<8212bda4>] kernel_init_freeable+0x1c6/0x236 [<81b9238b>] kernel_init+0xb/0xd0 [<81bb0080>] ret_from_kernel_thread+0x20/0x30 I believe the core of the problem is that print_PIC() calls printk() from under i8259A_lock. I've checked and that doesn't seem to happen anywhere else in the kernel. So let's move printk() from under that lock. As a side note this problem has existed for a long time but it was uncovered by my patch resulting in extended lockdep coverage of printk code. Reported-by: Jet Chen Signed-off-by: Jan Kara --- arch/x86/kernel/apic/io_apic.c | 19 +++++++++---------- 1 file changed, 9 insertions(+), 10 deletions(-) diff --git a/arch/x86/kernel/apic/io_apic.c b/arch/x86/kernel/apic/io_apic.c index 6ad4658de705..b815a4c9e5e5 100644 --- a/arch/x86/kernel/apic/io_apic.c +++ b/arch/x86/kernel/apic/io_apic.c @@ -1770,7 +1770,7 @@ __apicdebuginit(void) print_local_APICs(int maxcpu) __apicdebuginit(void) print_PIC(void) { - unsigned int v; + unsigned int v0, v1, v2; unsigned long flags; if (!legacy_pic->nr_legacy_irqs) @@ -1780,24 +1780,23 @@ __apicdebuginit(void) print_PIC(void) raw_spin_lock_irqsave(&i8259A_lock, flags); - v = inb(0xa1) << 8 | inb(0x21); - printk(KERN_DEBUG "... PIC IMR: %04x\n", v); - - v = inb(0xa0) << 8 | inb(0x20); - printk(KERN_DEBUG "... PIC IRR: %04x\n", v); + v0 = inb(0xa1) << 8 | inb(0x21); + v1 = inb(0xa0) << 8 | inb(0x20); outb(0x0b,0xa0); outb(0x0b,0x20); - v = inb(0xa0) << 8 | inb(0x20); + v2 = inb(0xa0) << 8 | inb(0x20); outb(0x0a,0xa0); outb(0x0a,0x20); raw_spin_unlock_irqrestore(&i8259A_lock, flags); - printk(KERN_DEBUG "... PIC ISR: %04x\n", v); + printk(KERN_DEBUG "... PIC IMR: %04x\n", v0); + printk(KERN_DEBUG "... PIC IRR: %04x\n", v1); + printk(KERN_DEBUG "... PIC ISR: %04x\n", v2); - v = inb(0x4d1) << 8 | inb(0x4d0); - printk(KERN_DEBUG "... PIC ELCR: %04x\n", v); + v0 = inb(0x4d1) << 8 | inb(0x4d0); + printk(KERN_DEBUG "... PIC ELCR: %04x\n", v0); } static int __initdata show_lapic = 1;