[PATCH -tip] x86,trace: Add rcu_irq_enter/exit() in smp_trace_reschedule_interrupt()

From: Seiji Aguchi
Date: Mon Jun 24 2013 - 16:21:55 EST


Reschedule vector tracepoints may be called in cpu idle state.
This causes lockdep check warning below.
So, add rcu_irq_enter/exit() to smp_trace_reschedule_interrupt().

[ 50.720557] Testing event reschedule_exit:
[ 50.721349]
[ 50.721502] ===============================
[ 50.721835] [ INFO: suspicious RCU usage. ]
[ 50.722169] 3.10.0-rc6-00004-gcf910e8 #190 Not tainted
[ 50.722582] -------------------------------
[ 50.722915] /c/kernel-tests/src/linux/arch/x86/include/asm/trace/irq_vectors.h:50 suspicious rcu_dereference_check() usage!
[ 50.723770]
[ 50.723770] other info that might help us debug this:
[ 50.723770]
[ 50.724385]
[ 50.724385] RCU used illegally from idle CPU!
[ 50.724385] rcu_scheduler_active = 1, debug_locks = 0
[ 50.725232] RCU used illegally from extended quiescent state!
[ 50.725690] no locks held by swapper/0/0.
[ 50.726010]
[ 50.726010] stack backtrace:
[ 50.726359] CPU: 0 PID: 0 Comm: swapper/0 Not tainted 3.10.0-rc6-00004-gcf910e8 #190
[ 50.726965] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011

[ 50.727417] 00000001 00000001 79c53f04 798bd9f9 79c53f2c 79077a70 79b412c6 79b41fd1
[ 50.728159] 00000001 00000000 79c5ef8c 87147c58 00000000 79c55800 79c53f38 79010b65
[ 50.728849] 79c52000 79c53f7c 798c720e 79c52000 79c5ef8c 00000004 00000000 79c55800
[ 50.729532] Call Trace:
[ 50.729730] [<798bd9f9>] dump_stack+0x16/0x18
[ 50.730072] [<79077a70>] lockdep_rcu_suspicious+0xf2/0xfa
[ 50.730498] [<79010b65>] smp_trace_reschedule_interrupt+0x1c8/0x1d0
[ 50.730979] [<798c720e>] trace_reschedule_interrupt+0x36/0x3c
[ 50.731214] [<7901875f>] ? native_safe_halt+0x5/0x7
[ 50.731214] [<790085cc>] default_idle+0xb1/0x1e2
[ 50.731214] [<79008d05>] arch_cpu_idle+0xe/0x10
[ 50.731214] [<79069ddf>] cpu_startup_entry+0x1e4/0x2c3
[ 50.731214] [<798adb34>] rest_init+0x12c/0x132
[ 50.731214] [<798ada08>] ? __read_lock_failed+0x14/0x14
[ 50.731214] [<79d309e4>] start_kernel+0x38d/0x393
[ 50.731214] [<79d30489>] ? repair_env_string+0x51/0x51
[ 50.731214] [<79d302c3>] i386_start_kernel+0x79/0x7d
[ 50.771947] OK
[ 50.772099] Testing event reschedule_entry: OK

Signed-off-by: Seiji Aguchi <seiji.aguchi@xxxxxxx>
---
arch/x86/kernel/smp.c | 2 ++
1 files changed, 2 insertions(+), 0 deletions(-)

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();
/*
* KVM uses this interrupt to force a cpu out of guest mode
*/
--
1.7.1

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