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

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Message-ID: <51C8AA31.3070208@hds.com>
Date:	Mon, 24 Jun 2013 16:21:05 -0400
From:	Seiji Aguchi <seiji.aguchi@....com>
To:	linux-kernel@...r.kernel.org, x86@...nel.org, rostedt@...dmis.org,
	hpa@...or.com
CC:	mingo@...e.hu, tglx@...utronix.de
Subject: [PATCH -tip] x86,trace: Add rcu_irq_enter/exit() in smp_trace_reschedule_interrupt()

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@....com>
---
 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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