From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756249Ab1ILXhV (ORCPT ); Mon, 12 Sep 2011 19:37:21 -0400 Received: from claw.goop.org ([74.207.240.146]:34541 "EHLO claw.goop.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755559Ab1ILXhT (ORCPT ); Mon, 12 Sep 2011 19:37:19 -0400 Message-ID: <4E6E97AC.8020707@goop.org> Date: Mon, 12 Sep 2011 16:37:16 -0700 From: Jeremy Fitzhardinge User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:6.0.2) Gecko/20110906 Thunderbird/6.0.2 MIME-Version: 1.0 To: Linus Torvalds CC: "xen-devel@lists.xensource.com" , Linux Kernel Mailing List , Konrad Rzeszutek Wilk , Avi Kivity Subject: Re: [GIT PULL] Little bugfix to prevent recursion with tracing timestamps References: <4E6E92AB.5050504@goop.org> In-Reply-To: <4E6E92AB.5050504@goop.org> X-Enigmail-Version: 1.3.1 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org -----BEGIN PGP SIGNED MESSAGE----- Hash: SHA256 [ Sigh, for some reason that doesn't verify. Let's see if this works. Anyway, I pushed a signed tag "upstream-bugfix-for-linus" on that changeset. - J ] Hi Linus, When starting a PV kernel under Xen with full boot-time trace testing enabled, it crashes due to infinite recursion. In principle it could happen at other times too (when just using preempt tracing perhaps?). This fixes it. BTW, I think this same problem also affects KVM. Erm, I'm not sure how to authenticate this github as being really from me; I'm signing the mail with my long-standing pgp key in the hope that it helps... Also, the patch is self-evident. Thanks, J The following changes since commit b6fd41e29dea9c6753b1843a77e50433e6123bcb: Linux 3.1-rc6 (2011-09-12 14:02:02 -0700) are available in the git repository at: git://github.com/jsgf/linux-xen.git upstream/bugfix Jeremy Fitzhardinge (1): xen: use non-tracing preempt in xen_clocksource_read() arch/x86/xen/time.c | 5 +++-- 1 files changed, 3 insertions(+), 2 deletions(-) diff --git a/arch/x86/xen/time.c b/arch/x86/xen/time.c index 5158c50..163b467 100644 - - --- a/arch/x86/xen/time.c +++ b/arch/x86/xen/time.c @@ -168,9 +168,10 @@ cycle_t xen_clocksource_read(void) struct pvclock_vcpu_time_info *src; cycle_t ret; - - - src = &get_cpu_var(xen_vcpu)->time; + preempt_disable_notrace(); + src = &__get_cpu_var(xen_vcpu)->time; ret = pvclock_clocksource_read(src); - - - put_cpu_var(xen_vcpu); + preempt_enable_notrace(); return ret; } -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.11 (GNU/Linux) Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org/ iQEkBAEBCAAGBQJObpesAAoJEAUkni6MUg7HMnAIP0bR68/akTif/RVfis0Cot/a ONlz5GsGGA7AlHfp/l/M8GZo5fUIC7Ja+EqTnpUWMNbubLoe5kALt5k/uQwADtoI cyvi5j2tlXDGDZOgQ900pQQYMBFVwaCm5XwSuDTbysPUx4v7E5Ha/RL2xapbuFnP txCyO62xx4EsKqkupM4qnTCBId6ksRNo9EVESxFzpJk/l0fabTLM98RigA1KJmdo +Rr+1SzfNnNQLLXG48EHITthfYaBOw9jyGanbe5i9Iw79J85vjI5V65TMlDztWaN kyUGiWD9f1i9ixCO31qhszdRire8c2N8hDTTN5z1919Gtlkq93Oj3F8zkUlbapyh tD4e8GObdA== =MA3l -----END PGP SIGNATURE-----