From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758356Ab2GKS1t (ORCPT ); Wed, 11 Jul 2012 14:27:49 -0400 Received: from mail-gh0-f174.google.com ([209.85.160.174]:47918 "EHLO mail-gh0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758325Ab2GKS1k (ORCPT ); Wed, 11 Jul 2012 14:27:40 -0400 From: Frederic Weisbecker To: "Paul E. McKenney" Cc: LKML , Frederic Weisbecker , Alessio Igor Bogani , Andrew Morton , Avi Kivity , Chris Metcalf , Christoph Lameter , Geoff Levand , Gilad Ben Yossef , Hakan Akkan , "H. Peter Anvin" , Ingo Molnar , Josh Triplett , Kevin Hilman , Max Krasnyansky , Peter Zijlstra , Stephen Hemminger , Steven Rostedt , Sven-Thorsten Dietrich , Thomas Gleixner Subject: [PATCH 10/11] x86: Exit RCU extended QS on notify resume Date: Wed, 11 Jul 2012 20:26:39 +0200 Message-Id: <1342031200-22731-11-git-send-email-fweisbec@gmail.com> X-Mailer: git-send-email 1.7.5.4 In-Reply-To: <1342031200-22731-1-git-send-email-fweisbec@gmail.com> References: <1342031200-22731-1-git-send-email-fweisbec@gmail.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org do_notify_resume() may be called on irq or exception exit. But at that time the exception has already called rcu_user_enter() and the irq has already called rcu_irq_exit(). Since it can use RCU read side critical section, we must call rcu_user_exit() before doing anything there. Then we must call back rcu_user_enter() after this function because we know we are going to userspace from there. This complete support for userspace RCU extended quiescent state in x86-64. Signed-off-by: Frederic Weisbecker Cc: Alessio Igor Bogani Cc: Andrew Morton Cc: Avi Kivity Cc: Chris Metcalf Cc: Christoph Lameter Cc: Geoff Levand Cc: Gilad Ben Yossef Cc: Hakan Akkan Cc: H. Peter Anvin Cc: Ingo Molnar Cc: Josh Triplett Cc: Kevin Hilman Cc: Max Krasnyansky Cc: Peter Zijlstra Cc: Stephen Hemminger Cc: Steven Rostedt Cc: Sven-Thorsten Dietrich Cc: Thomas Gleixner --- arch/x86/Kconfig | 1 + arch/x86/kernel/signal.c | 4 ++++ 2 files changed, 5 insertions(+), 0 deletions(-) diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig index c70684f..38dfcc2 100644 --- a/arch/x86/Kconfig +++ b/arch/x86/Kconfig @@ -95,6 +95,7 @@ config X86 select KTIME_SCALAR if X86_32 select GENERIC_STRNCPY_FROM_USER select GENERIC_STRNLEN_USER + select HAVE_RCU_USER_QS if X86_64 config INSTRUCTION_DECODER def_bool (KPROBES || PERF_EVENTS || UPROBES) diff --git a/arch/x86/kernel/signal.c b/arch/x86/kernel/signal.c index 21af737..5cc2579 100644 --- a/arch/x86/kernel/signal.c +++ b/arch/x86/kernel/signal.c @@ -776,6 +776,8 @@ static void do_signal(struct pt_regs *regs) void do_notify_resume(struct pt_regs *regs, void *unused, __u32 thread_info_flags) { + rcu_user_exit(); + #ifdef CONFIG_X86_MCE /* notify userspace of pending MCEs */ if (thread_info_flags & _TIF_MCE_NOTIFY) @@ -801,6 +803,8 @@ do_notify_resume(struct pt_regs *regs, void *unused, __u32 thread_info_flags) #ifdef CONFIG_X86_32 clear_thread_flag(TIF_IRET); #endif /* CONFIG_X86_32 */ + + rcu_user_enter(); } void signal_fault(struct pt_regs *regs, void __user *frame, char *where) -- 1.7.5.4