linux-kernel - RE: [PATCH -tip] x86,trace: Add rcu_irq_enter/exit() in smp_trace_reschedule

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Message-ID: <A5ED84D3BB3A384992CBB9C77DEDA4D443E0FE25@USINDEM103.corp.hds.com>
Date:	Fri, 28 Jun 2013 15:13:14 +0000
From:	Seiji Aguchi <seiji.aguchi@....com>
To:	Steven Rostedt <rostedt@...dmis.org>
CC:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"x86@...nel.org" <x86@...nel.org>, "hpa@...or.com" <hpa@...or.com>,
	"mingo@...e.hu" <mingo@...e.hu>,
	"tglx@...utronix.de" <tglx@...utronix.de>,
	"Paul E. McKenney" <paulmck@...ibm.com>,
	Peter Zijlstra <peterz@...radead.org>
Subject: RE: [PATCH -tip] x86,trace: Add rcu_irq_enter/exit() in
 smp_trace_reschedule_interrupt()

> > diff --git a/arch/x86/kernel/smp.c b/arch/x86/kernel/smp.c
> > index f4fe0b8..b959056 100644
> > --- a/arch/x86/kernel/smp.c
> > +++ b/arch/x86/kernel/smp.c
> > @@ -268,9 +268,11 @@ void smp_reschedule_interrupt(struct pt_regs *regs)
> >  void smp_trace_reschedule_interrupt(struct pt_regs *regs)
> >  {
> >  	ack_APIC_irq();
> > +	rcu_irq_enter();
> >  	trace_reschedule_entry(RESCHEDULE_VECTOR);
> >  	__smp_reschedule_interrupt();
> >  	trace_reschedule_exit(RESCHEDULE_VECTOR);
> > +	rcu_irq_exit();
> 
> The question is, should we add normal irq_enter/exit here? As that
> should be OK to nest. There's a comment in scheduler_ipi():

> Either way, the tracepoint requires rcu but for accuracy it also
> requires irq_enter() (tracepoints record the irq context), thus, the
> tracepoint interrupt handler should be calling irq_enter() and not
> rcu_irq_enter() (irq_enter() calls rcu_irq_enter())

OK.
So,  ack_APIC_irq() and irq_enter() are needed.
It can be shared with smp_call_function() and smp_call_function_single() like this.
I will update the patch.

arch/x86/kernel/smp.c |   23 ++++++++++++-----------
 1 files changed, 12 insertions(+), 11 deletions(-)

diff --git a/arch/x86/kernel/smp.c b/arch/x86/kernel/smp.c
index f4fe0b8..732b618 100644
--- a/arch/x86/kernel/smp.c
+++ b/arch/x86/kernel/smp.c
@@ -265,23 +265,24 @@ void smp_reschedule_interrupt(struct pt_regs *regs)
 	 */
 }
 
-void smp_trace_reschedule_interrupt(struct pt_regs *regs)
+static inline void smp_entering_irq(void)
 {
 	ack_APIC_irq();
+	irq_enter();
+}
+
+void smp_trace_reschedule_interrupt(struct pt_regs *regs)
+{
+	smp_entering_irq();
 	trace_reschedule_entry(RESCHEDULE_VECTOR);
 	__smp_reschedule_interrupt();
 	trace_reschedule_exit(RESCHEDULE_VECTOR);
+	exiting_irq();
 	/*
 	 * KVM uses this interrupt to force a cpu out of guest mode
 	 */
 }
 
-static inline void call_function_entering_irq(void)
-{
-	ack_APIC_irq();
-	irq_enter();
-}
-
 static inline void __smp_call_function_interrupt(void)
 {
 	generic_smp_call_function_interrupt();
@@ -290,14 +291,14 @@ static inline void __smp_call_function_interrupt(void)
 
 void smp_call_function_interrupt(struct pt_regs *regs)
 {
-	call_function_entering_irq();
+	smp_entering_irq();
 	__smp_call_function_interrupt();
 	exiting_irq();
 }
 
 void smp_trace_call_function_interrupt(struct pt_regs *regs)
 {
-	call_function_entering_irq();
+	smp_entering_irq();
 	trace_call_function_entry(CALL_FUNCTION_VECTOR);
 	__smp_call_function_interrupt();
 	trace_call_function_exit(CALL_FUNCTION_VECTOR);
@@ -312,14 +313,14 @@ static inline void __smp_call_function_single_interrupt(void)
 
 void smp_call_function_single_interrupt(struct pt_regs *regs)
 {
-	call_function_entering_irq();
+	smp_entering_irq();
 	__smp_call_function_single_interrupt();
 	exiting_irq();
 }
 
 void smp_trace_call_function_single_interrupt(struct pt_regs *regs)
 {
-	call_function_entering_irq();
+	smp_entering_irq();
 	trace_call_function_single_entry(CALL_FUNCTION_SINGLE_VECTOR);
 	__smp_call_function_single_interrupt();
 	trace_call_function_single_exit(CALL_FUNCTION_SINGLE_VECTOR);
-- 
1.7.1