linux-kernel - [tip:x86/urgent] x86/smp: Add irq_enter/exit() in smp_reschedule

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Date:   Fri, 14 Oct 2016 05:19:32 -0700
From:   tip-bot for Wanpeng Li <tipbot@...or.com>
To:     linux-tip-commits@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org, hpa@...or.com, mingo@...nel.org,
        kernellwp@...il.com, tglx@...utronix.de, peterz@...radead.org,
        wanpeng.li@...mail.com, efault@....de
Subject: [tip:x86/urgent] x86/smp: Add irq_enter/exit() in
 smp_reschedule_interrupt()

Commit-ID:  1ec6ec14a2943f6f611fc1d5fb2d4eaa85bd9d72
Gitweb:     http://git.kernel.org/tip/1ec6ec14a2943f6f611fc1d5fb2d4eaa85bd9d72
Author:     Wanpeng Li <kernellwp@...il.com>
AuthorDate: Fri, 14 Oct 2016 09:48:53 +0800
Committer:  Thomas Gleixner <tglx@...utronix.de>
CommitDate: Fri, 14 Oct 2016 14:14:20 +0200

x86/smp: Add irq_enter/exit() in smp_reschedule_interrupt()

 ===============================
 [ INFO: suspicious RCU usage. ]
 4.8.0+ #24 Not tainted
 -------------------------------
 ./arch/x86/include/asm/msr-trace.h:47 suspicious rcu_dereference_check() usage!
 
 other info that might help us debug this:
 
 RCU used illegally from idle CPU!
 rcu_scheduler_active = 1, debug_locks = 0
 RCU used illegally from extended quiescent state!
 no locks held by swapper/1/0.
 
  [<ffffffff9d492b95>] do_trace_write_msr+0x135/0x140
  [<ffffffff9d06f860>] native_write_msr+0x20/0x30
  [<ffffffff9d065fad>] native_apic_msr_eoi_write+0x1d/0x30
  [<ffffffff9d05bd1d>] smp_reschedule_interrupt+0x1d/0x30
  [<ffffffff9d8daec6>] reschedule_interrupt+0x96/0xa0

Reschedule interrupt may be called in cpu idle state. This causes lockdep 
check warning above. 

Add irq_enter/exit() in smp_reschedule_interrupt(), irq_enter() tells the RCU 
subsystems to end the extended quiescent state, so the following trace call in 
ack_APIC_irq() works correctly.

Signed-off-by: Wanpeng Li <wanpeng.li@...mail.com>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Mike Galbraith <efault@....de>
Link: http://lkml.kernel.org/r/1476409733-5133-1-git-send-email-wanpeng.li@hotmail.com
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>

---
 arch/x86/kernel/smp.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/arch/x86/kernel/smp.c b/arch/x86/kernel/smp.c
index 658777c..ac2ee87 100644
--- a/arch/x86/kernel/smp.c
+++ b/arch/x86/kernel/smp.c
@@ -259,8 +259,10 @@ static inline void __smp_reschedule_interrupt(void)
 
 __visible void smp_reschedule_interrupt(struct pt_regs *regs)
 {
+	irq_enter();
 	ack_APIC_irq();
 	__smp_reschedule_interrupt();
+	irq_exit();
 	/*
 	 * KVM uses this interrupt to force a cpu out of guest mode
 	 */