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x86/apic: Fix suspicious RCU usage in smp_trace_call_function_interru…
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…pt()

Since 4.4, I've been able to trigger this occasionally:

===============================
[ INFO: suspicious RCU usage. ]
4.5.0-rc7-think+ #3 Not tainted
Cc: Andi Kleen <ak@linux.intel.com>
Link: http://lkml.kernel.org/r/20160315012054.GA17765@codemonkey.org.uk
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

-------------------------------
./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 = 1
RCU used illegally from extended quiescent state!
no locks held by swapper/3/0.

stack backtrace:
CPU: 3 PID: 0 Comm: swapper/3 Not tainted 4.5.0-rc7-think+ #3
 ffffffff92f821e0 1f3e5c340597d7fc ffff880468e07f10 ffffffff92560c2a
 ffff880462145280 0000000000000001 ffff880468e07f40 ffffffff921376a6
 ffffffff93665ea0 0000cc7c876d28da 0000000000000005 ffffffff9383dd60
Call Trace:
 <IRQ>  [<ffffffff92560c2a>] dump_stack+0x67/0x9d
 [<ffffffff921376a6>] lockdep_rcu_suspicious+0xe6/0x100
 [<ffffffff925ae7a7>] do_trace_write_msr+0x127/0x1a0
 [<ffffffff92061c83>] native_apic_msr_eoi_write+0x23/0x30
 [<ffffffff92054408>] smp_trace_call_function_interrupt+0x38/0x360
 [<ffffffff92d1ca60>] trace_call_function_interrupt+0x90/0xa0
 <EOI>  [<ffffffff92ac5124>] ? cpuidle_enter_state+0x1b4/0x520

Move the entering_irq() call before ack_APIC_irq(), because entering_irq()
tells the RCU susbstems to end the extended quiescent state, so that the
following trace call in ack_APIC_irq() works correctly.

Suggested-by: Andi Kleen <ak@linux.intel.com>
Fixes: 4787c36 "x86/tracing: Add irq_enter/exit() in smp_trace_reschedule_interrupt()"
Signed-off-by: Dave Jones <davej@codemonkey.org.uk>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: stable@vger.kernel.org
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kernelslacker authored and KAGA-KOKO committed Mar 18, 2016
1 parent c29016c commit 7834c10
Showing 1 changed file with 1 addition and 1 deletion.
2 changes: 1 addition & 1 deletion arch/x86/include/asm/apic.h
Original file line number Diff line number Diff line change
Expand Up @@ -643,8 +643,8 @@ static inline void entering_irq(void)

static inline void entering_ack_irq(void)
{
ack_APIC_irq();
entering_irq();
ack_APIC_irq();
}

static inline void ipi_entering_ack_irq(void)
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