[PATCH] x86/smp: Add irq_enter/exit() in smp_reschedule_interrupt()

From: Wanpeng Li
Date: Thu Oct 13 2016 - 21:49:12 EST

[ 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.

stack backtrace:
CPU: 1 PID: 0 Comm: swapper/1 Not tainted 4.8.0+ #24
Hardware name: Dell Inc. OptiPlex 7020/0F5C5X, BIOS A03 01/08/2015
ffff90285de03f58 ffffffff9d44a0c9 ffff90285ca5d100 0000000000000001
ffff90285de03f88 ffffffff9d0ebd67 ffff902845165410 000000000000080b
0000000000000000 0000000000000000 ffff90285de03fb8 ffffffff9d492b95
Call Trace:
<IRQ> [<ffffffff9d44a0c9>] dump_stack+0x99/0xd0
[<ffffffff9d0ebd67>] lockdep_rcu_suspicious+0xe7/0x120
[<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
<EOI> [<ffffffff9d732634>] ? cpuidle_enter_state+0xe4/0x360
[<ffffffff9d73261f>] ? cpuidle_enter_state+0xcf/0x360
[<ffffffff9d7328e7>] cpuidle_enter+0x17/0x20
[<ffffffff9d0e1a73>] call_cpuidle+0x23/0x50
[<ffffffff9d0e1d0c>] cpu_startup_entry+0x15c/0x280
[<ffffffff9d05ce64>] start_secondary+0x154/0x180

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.

Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Mike Galbraith <efault@xxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Signed-off-by: Wanpeng Li <wanpeng.li@xxxxxxxxxxx>
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();
+ irq_exit();
* KVM uses this interrupt to force a cpu out of guest mode