From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758806Ab3B1QkU (ORCPT ); Thu, 28 Feb 2013 11:40:20 -0500 Received: from e7.ny.us.ibm.com ([32.97.182.137]:57713 "EHLO e7.ny.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753298Ab3B1QkS (ORCPT ); Thu, 28 Feb 2013 11:40:18 -0500 Date: Thu, 28 Feb 2013 08:38:47 -0800 From: "Paul E. McKenney" To: Li Zhong Cc: LKML , Frederic Weisbecker Subject: Re: [RFC PATCH] context_tracking/rcu: don't function trace before rcu_user_exit() finishes Message-ID: <20130228163847.GA3566@linux.vnet.ibm.com> Reply-To: paulmck@linux.vnet.ibm.com References: <1362039970.18895.28.camel@ThinkPad-T5421.cn.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1362039970.18895.28.camel@ThinkPad-T5421.cn.ibm.com> User-Agent: Mutt/1.5.21 (2010-09-15) X-Content-Scanned: Fidelis XPS MAILER x-cbid: 13022816-5806-0000-0000-00002024DE43 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Feb 28, 2013 at 04:26:10PM +0800, Li Zhong wrote: > 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(). And I have to ask... Do we really need the rcu_user_notrace? Why not just label the functions as notrace? Thanx, Paul > 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(), > >