From patchwork Tue Sep 4 02:47:56 2012 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Anton Blanchard X-Patchwork-Id: 181483 Return-Path: X-Original-To: patchwork-incoming@ozlabs.org Delivered-To: patchwork-incoming@ozlabs.org Received: from ozlabs.org (localhost [IPv6:::1]) by ozlabs.org (Postfix) with ESMTP id DFBB22C033C for ; Tue, 4 Sep 2012 12:48:26 +1000 (EST) Received: from kryten (ppp121-44-116-176.lns20.syd6.internode.on.net [121.44.116.176]) (using TLSv1.2 with cipher DHE-RSA-AES128-SHA (128/128 bits)) (Client did not present a certificate) by ozlabs.org (Postfix) with ESMTPSA id 0F0812C0108; Tue, 4 Sep 2012 12:47:57 +1000 (EST) Date: Tue, 4 Sep 2012 12:47:56 +1000 From: Anton Blanchard To: benh@kernel.crashing.org, paulus@samba.org Subject: [PATCH 1/4] powerpc: Update DSCR on all CPUs when writing sysfs dscr_default Message-ID: <20120904124756.4ddeb535@kryten> X-Mailer: Claws Mail 3.8.0 (GTK+ 2.24.10; x86_64-pc-linux-gnu) Mime-Version: 1.0 Cc: linuxppc-dev@lists.ozlabs.org X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: linuxppc-dev-bounces+patchwork-incoming=ozlabs.org@lists.ozlabs.org Sender: "Linuxppc-dev" Writing to dscr_default in sysfs doesn't actually change the DSCR - we rely on a context switch on each CPU to do the work. There is no guarantee we will get a context switch in a reasonable amount of time so fire off an IPI to force an immediate change. This issue was found with the following test case: http://ozlabs.org/~anton/junkcode/dscr_explicit_test.c Signed-off-by: Anton Blanchard Cc: # 3.0+ Index: b/arch/powerpc/kernel/sysfs.c =================================================================== --- a/arch/powerpc/kernel/sysfs.c +++ b/arch/powerpc/kernel/sysfs.c @@ -194,6 +194,12 @@ static ssize_t show_dscr_default(struct return sprintf(buf, "%lx\n", dscr_default); } +static void update_dscr(void *dummy) +{ + if (!current->thread.dscr_inherit) + mtspr(SPRN_DSCR, dscr_default); +} + static ssize_t __used store_dscr_default(struct device *dev, struct device_attribute *attr, const char *buf, size_t count) @@ -206,6 +212,8 @@ static ssize_t __used store_dscr_default return -EINVAL; dscr_default = val; + on_each_cpu(update_dscr, NULL, 1); + return count; }