Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754476AbbGVFlN (ORCPT ); Wed, 22 Jul 2015 01:41:13 -0400 Received: from mga01.intel.com ([192.55.52.88]:34493 "EHLO mga01.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751609AbbGVFlL (ORCPT ); Wed, 22 Jul 2015 01:41:11 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.15,521,1432623600"; d="scan'208";a="610522406" Message-ID: <55AF2C68.5010304@intel.com> Date: Wed, 22 Jul 2015 13:38:48 +0800 From: Pan Xinhui User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.5.0 MIME-Version: 1.0 To: "linux-kernel@vger.kernel.org" CC: Thomas Gleixner , mingo@redhat.com, hpa@zytor.com, x86@kernel.org, bp@suse.de, toshi.kani@hp.com, jgross@suse.com, mcgrof@suse.com, "mnipxh@163.com" , "yanmin_zhang@linux.intel.com" Subject: [PATCH V3] x86/mm/pat: Do a small optimization and fix in reserve_memtype 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 Content-Length: 2311 Lines: 67 From: Pan Xinhui It's more reasonable to unlock memtype_lock right after rbt_memtype_check_insert. memtype_lock protects all data stored in rb-tree from multiple access. It's not cool to call kfree, pr_info, etc with this lock held. So move spin_unlock a little ahead. If *new* succeed to be stored into the rb-tree, we might hit panic. Because we access *new* in dprintk "cattr_name(new->type)". Data stored in the rb-tree might be freed at any possbile time. It's abviously wrong to access such data without lock held. As new->type might be changed in rbt_memtype_check_insert, so save new->type to actual_type, then use actual_type in dprintk. Signed-off-by: Pan Xinhui --- change from v2: update comments. change from V1: fix an access of *new* without memtype_lock held. --- arch/x86/mm/pat.c | 15 +++++++++------ 1 file changed, 9 insertions(+), 6 deletions(-) diff --git a/arch/x86/mm/pat.c b/arch/x86/mm/pat.c index 188e3e0..894a096 100644 --- a/arch/x86/mm/pat.c +++ b/arch/x86/mm/pat.c @@ -538,22 +538,25 @@ int reserve_memtype(u64 start, u64 end, enum page_cache_mode req_type, new->type = actual_type; spin_lock(&memtype_lock); - err = rbt_memtype_check_insert(new, new_type); + /* + * new->type might be changed in rbt_memtype_check_insert. + * So save new->type to actual_type as dprintk uses it. + * We are not allowed to touch new after unlocking memtype_lock. + */ + actual_type = new->type; + spin_unlock(&memtype_lock); + if (err) { pr_info("x86/PAT: reserve_memtype failed [mem %#010Lx-%#010Lx], track %s, req %s\n", start, end - 1, cattr_name(new->type), cattr_name(req_type)); kfree(new); - spin_unlock(&memtype_lock); - return err; } - spin_unlock(&memtype_lock); - dprintk("reserve_memtype added [mem %#010Lx-%#010Lx], track %s, req %s, ret %s\n", - start, end - 1, cattr_name(new->type), cattr_name(req_type), + start, end - 1, cattr_name(actual_type), cattr_name(req_type), new_type ? cattr_name(*new_type) : "-"); return err; -- 1.9.1 -- 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/