From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from VA3EHSOBE001.bigfish.com (va3ehsobe001.messaging.microsoft.com [216.32.180.11]) (using TLSv1 with cipher AES128-SHA (128/128 bits)) (Client CN "mail.global.frontbridge.com", Issuer "Cybertrust SureServer Standard Validation CA" (verified OK)) by ozlabs.org (Postfix) with ESMTPS id B5F96B70D6 for ; Tue, 5 Oct 2010 07:26:51 +1100 (EST) Received: from mail58-va3 (localhost.localdomain [127.0.0.1]) by mail58-va3-R.bigfish.com (Postfix) with ESMTP id 4C2C2C401B7 for ; Mon, 4 Oct 2010 20:26:47 +0000 (UTC) Received: from VA3EHSMHS036.bigfish.com (unknown [10.7.14.241]) by mail58-va3.bigfish.com (Postfix) with ESMTP id 024EB3E0046 for ; Mon, 4 Oct 2010 20:26:46 +0000 (UTC) Received: from az33smr01.freescale.net (az33smr01.freescale.net [10.64.34.199]) by de01egw01.freescale.net (8.14.3/8.14.3) with ESMTP id o94KQjn6012480 for ; Mon, 4 Oct 2010 13:26:46 -0700 (MST) Received: from az33exm25.fsl.freescale.net (az33exm25.am.freescale.net [10.64.32.16]) by az33smr01.freescale.net (8.13.1/8.13.0) with ESMTP id o94KN0wg022472 for ; Mon, 4 Oct 2010 15:23:01 -0500 (CDT) Date: Mon, 4 Oct 2010 15:22:59 -0500 From: Scott Wood To: Nick Piggin , Subject: in_atomic() check in page_cache_get_speculative() Message-ID: <20101004152259.25c56ad2@udp111988uds.am.freescale.net> MIME-Version: 1.0 Content-Type: text/plain; charset="US-ASCII" List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , I'm seeing the in_atomic() check in page_cache_get_speculative() (linux/pagemap.h:138) fail when running e500 KVM with . It's coming from get_user_pages_fast(), from KVM's hva_to_pfn(). This is on kvm.git plus a few local patches that should be completely unrelated, but it looks like this code hasn't changed much in a couple years. Interrupts are disabled by get_user_pages_fast(), but apparently preemption was not separately disabled. The comment in page_cache_get_speculative() says that preemption disabling is done by rcu_read_lock(), and that "this function must be called inside the same rcu_read_lock() section as has been used to lookup the page in the pagecache radix-tree (or page table)". Where is this RCU lock supposed to be acquired? I don't see any RCU in arch/powerpc/mm/gup.c. Is it buried in some macro or function call? -Scott