From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933826AbaE3QT7 (ORCPT ); Fri, 30 May 2014 12:19:59 -0400 Received: from bombadil.infradead.org ([198.137.202.9]:50067 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932378AbaE3QT6 (ORCPT ); Fri, 30 May 2014 12:19:58 -0400 Date: Fri, 30 May 2014 18:19:48 +0200 From: Peter Zijlstra To: Jan Kara Cc: Jet Chen , Fengguang Wu , Yuanhan Liu , Linux Kernel Mailing List , Sasha Levin , Peter Hurley , Andrew Morton Subject: Re: [prink] BUG: spinlock lockup suspected on CPU#0, swapper/1 Message-ID: <20140530161948.GZ13658@twins.programming.kicks-ass.net> References: <538808FD.3060707@intel.com> <20140530155051.GD2419@quack.suse.cz> <20140530161647.GD11096@twins.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="V2AZ19bMCakBLong" Content-Disposition: inline In-Reply-To: <20140530161647.GD11096@twins.programming.kicks-ass.net> User-Agent: Mutt/1.5.21 (2012-12-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org --V2AZ19bMCakBLong Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Fri, May 30, 2014 at 06:16:47PM +0200, Peter Zijlstra wrote: > On Fri, May 30, 2014 at 05:50:51PM +0200, Jan Kara wrote: > > > [ 7.492350] =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D > > > [ 7.492350] [ INFO: possible circular locking dependency detected ] > > > [ 7.492350] 3.15.0-rc5-00567-gbafe980 #1 Not tainted > > > [ 7.492350] ------------------------------------------------------- > > > [ 7.492350] swapper/1 is trying to acquire lock: > > > [ 7.492350] (&irq_desc_lock_class){-.-...}, at: [<8107dc8c>] __ir= q_get_desc_lock+0x3c/0x70 > > > [ 7.492350]=20 > > > [ 7.492350] but task is already holding lock: > > > [ 7.492350] (&port_lock_key){......}, at: [<815f5b27>] serial8250= _startup+0x337/0x720 > > > [ 7.492350]=20 > > > [ 7.492350] which lock already depends on the new lock. > > > [ 7.492350]=20 > > > [ 7.492350]=20 > > > [ 7.492350] the existing dependency chain (in reverse order) is: > > > [ 7.492350]=20 > > > -> #2 (&port_lock_key){......}: > > > [ 7.492350] [<810750e5>] lock_acquire+0x85/0x190 > > > [ 7.492350] [<81baed9d>] _raw_spin_lock_irqsave+0x4d/0x60 > > > [ 7.492350] [<8106eb1c>] down_trylock+0xc/0x30 > > > [ 7.492350] [<8107b795>] console_trylock+0x15/0xb0 > > > [ 7.492350] [<8107be8f>] vprintk_emit+0x14f/0x4d0 > > > [ 7.492350] [<81b969b9>] printk+0x38/0x3a > > > [ 7.492350] [<82137f78>] print_ICs+0x5b/0x3e7 > > > [ 7.492350] [<8212bb41>] do_one_initcall+0x8b/0x128 > > > [ 7.492350] [<8212bd7d>] kernel_init_freeable+0x19f/0x236 > > > [ 7.492350] [<81b9238b>] kernel_init+0xb/0xd0 > > > [ 7.492350] [<81bb0080>] ret_from_kernel_thread+0x20/0x30 > > > > But this looks really strange. How can we possibly get port_lock_key = in > > down_trylock() which calls raw_spin_lock_irqsave() on console_sem->lock? > > That looks like some strange lockdep key aliasing issue? Peter do you h= ave > > any idea? >=20 > No, strange that, I can't say I've ever seen a bogus stracktrace in > lockdep reports like this. >=20 > So this is through: check_prev_add()->save_trace(). And that doesn't > reuse entries, at worst it can truncate a trace when we run out of > entries, but the above looks complete since it terminates in > lock_acquire(), which is the right place to be. >=20 > But its worse than that, the above trace should link i8259A_lock to > port_lock_key, and I can't see where we would have taken i8259A_lock > either. Oh, wait, I missed it, that would be: print_ICs()->print_PIC(), it takes that lock there. --V2AZ19bMCakBLong Content-Type: application/pgp-signature -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.12 (GNU/Linux) iQIcBAEBAgAGBQJTiK+kAAoJEHZH4aRLwOS6Gp8P/0K3cYmQYHZrBcLWwTMLCK8K 5RiMeFuinURegIengZAgl1PJUQ/IypnN8WIxUch0QeG82jC9hW+3R3l4KcdiwcJk AI6pDhRCwP6MCCGFzJQJKztE5ppkaVlayuWSGoD4zw5c73WVJURfrMqLm0hlqdms 3kzBA/95Ih46TqLFvIIWTjcUELqh2XCSsMtcgMHSNJpMdiKhfGOwb7bwzuiz2t9Z HoOnKfwKbIa5AY+qanMLvTO9XjIqmS2WhitjeD0sXasrjMU/Os/KZPNLCAQdc/rK Vw+Jf7gxsdTuVd+Yxua5M7i+1JS+RpVcQKRtfJQQ9t6ZsMDCuQMpml8l1RzfIl5Y pIyMPTJ0K5ekAD/711SY479ZheEGNgd2G1azn7GsgRGsKcK7uhCSJw+YPR1MLjAM uLd2xj0zM+FHsBIdPsXrFTRELFePUPIjXggI4ps+aLmtHGvfTaMBTm3S3GWBG2u5 654tmCpUWEbzWw8K+oa9He2ZL507ZASAxvsOfPCBtLiD8IVztDBboKmpVSmv7GYR /k/FuehksO8WpUZvQwpLOQLNXo6YKNHsb8iHKvBX3SN2A5NpnXkdNiKR/r5qdoeL WowAT4asb+BjX8g5VhkEmy3onzYo/qQpiaL2eaJOAgBT0fvXLaPM5KTrLnEFRyTb 7xDOyu+15T6Js6QhjJFt =7RIZ -----END PGP SIGNATURE----- --V2AZ19bMCakBLong--