From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753155Ab3B1I0f (ORCPT ); Thu, 28 Feb 2013 03:26:35 -0500 Received: from e23smtp02.au.ibm.com ([202.81.31.144]:45683 "EHLO e23smtp02.au.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751345Ab3B1I0e (ORCPT ); Thu, 28 Feb 2013 03:26:34 -0500 Message-ID: <1362039970.18895.28.camel@ThinkPad-T5421.cn.ibm.com> Subject: [RFC PATCH] context_tracking/rcu: don't function trace before rcu_user_exit() finishes From: Li Zhong To: LKML Cc: Frederic Weisbecker , "Paul E. McKenney" Date: Thu, 28 Feb 2013 16:26:10 +0800 Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.2.3-0ubuntu6 Content-Transfer-Encoding: 7bit Mime-Version: 1.0 X-Content-Scanned: Fidelis XPS MAILER x-cbid: 13022808-5490-0000-0000-000003094E59 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org I saw some RCU illegal usage from idle complaints when function tracer is enabled with forced context tracking. It seems that __schedule() might be called in function_trace_call() when it re-enables preemption(if preemption and irqs are both enabled). So at the places where we call rcu_user_exit(), we need make sure that no function tracer hooks could be called in preemption/irqs both enabled environment before rcu_user_exit() finishes, or we might cause illegal RCU usage in __schedule(). This patch tries to add notrace attribute to a couple of functions where the above could happen, including user_exit(), and a few callers of user_exit(). Signed-off-by: Li Zhong -- arch/x86/kernel/ptrace.c | 4 ++-- arch/x86/kernel/signal.c | 2 +- include/linux/rcupdate.h | 2 ++ kernel/context_tracking.c | 2 +- kernel/sched/core.c | 2 +- 5 files changed, 7 insertions(+), 5 deletions(-) diff --git a/arch/x86/kernel/ptrace.c b/arch/x86/kernel/ptrace.c index 29a8120..04659c2 100644 --- a/arch/x86/kernel/ptrace.c +++ b/arch/x86/kernel/ptrace.c @@ -1488,7 +1488,7 @@ void send_sigtrap(struct task_struct *tsk, struct pt_regs *regs, * We must return the syscall number to actually look up in the table. * This can be -1L to skip running any syscall at all. */ -long syscall_trace_enter(struct pt_regs *regs) +long rcu_user_notrace syscall_trace_enter(struct pt_regs *regs) { long ret = 0; @@ -1538,7 +1538,7 @@ out: return ret ?: regs->orig_ax; } -void syscall_trace_leave(struct pt_regs *regs) +void rcu_user_notrace syscall_trace_leave(struct pt_regs *regs) { bool step; diff --git a/arch/x86/kernel/signal.c b/arch/x86/kernel/signal.c index 6956299..10a9e5a 100644 --- a/arch/x86/kernel/signal.c +++ b/arch/x86/kernel/signal.c @@ -732,7 +732,7 @@ static void do_signal(struct pt_regs *regs) * notification of userspace execution resumption * - triggered by the TIF_WORK_MASK flags */ -void +void rcu_user_notrace do_notify_resume(struct pt_regs *regs, void *unused, __u32 thread_info_flags) { user_exit(); diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h index b758ce1..ecf9872 100644 --- a/include/linux/rcupdate.h +++ b/include/linux/rcupdate.h @@ -229,6 +229,7 @@ extern void rcu_user_enter(void); extern void rcu_user_exit(void); extern void rcu_user_enter_after_irq(void); extern void rcu_user_exit_after_irq(void); +#define rcu_user_notrace notrace #else static inline void rcu_user_enter(void) { } static inline void rcu_user_exit(void) { } @@ -236,6 +237,7 @@ static inline void rcu_user_enter_after_irq(void) { } static inline void rcu_user_exit_after_irq(void) { } static inline void rcu_user_hooks_switch(struct task_struct *prev, struct task_struct *next) { } +#define rcu_user_notrace #endif /* CONFIG_RCU_USER_QS */ extern void exit_rcu(void); diff --git a/kernel/context_tracking.c b/kernel/context_tracking.c index 65349f0..d3fc35f 100644 --- a/kernel/context_tracking.c +++ b/kernel/context_tracking.c @@ -83,7 +83,7 @@ void user_enter(void) * This call supports re-entrancy. This way it can be called from any exception * handler without needing to know if we came from userspace or not. */ -void user_exit(void) +void rcu_user_notrace user_exit(void) { unsigned long flags; diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 2b52431..c970e92 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -2973,7 +2973,7 @@ asmlinkage void __sched schedule(void) EXPORT_SYMBOL(schedule); #ifdef CONFIG_CONTEXT_TRACKING -asmlinkage void __sched schedule_user(void) +asmlinkage void __sched rcu_user_notrace schedule_user(void) { /* * If we come here after a random call to set_need_resched(),