Messages in this thread Patch in this message | | | Date | Mon, 14 Mar 2016 21:20:54 -0400 | From | Dave Jones <> | Subject | Fix suspicious RCU usage in msr tracing. |
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Since 4.4, I've been able to trigger this occasionally:
=============================== [ INFO: suspicious RCU usage. ] 4.5.0-rc7-think+ #3 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 = 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 [<ffffffff92ac54e7>] cpuidle_enter+0x17/0x20 [<ffffffff9212a984>] cpu_startup_entry+0x4e4/0x610 [<ffffffff9212a4a0>] ? default_idle_call+0x60/0x60 [<ffffffff921908e4>] ? clockevents_config_and_register+0x64/0x70 [<ffffffff92055843>] start_secondary+0x283/0x390 [<ffffffff920555c0>] ? set_cpu_sibling_map+0x970/0x970
Back in January, Andi suggested swapping the order in which we ack the APIC irq, so it too is protected by rcu. There was no follow-up, and it seems to work for me.
Cc: Andi Kleen <ak@linux.intel.com> Signed-off-by: Dave Jones <davej@codemonkey.org.uk>
diff --git a/arch/x86/include/asm/apic.h b/arch/x86/include/asm/apic.h index c80f6b6f3da2..e8c4fba52d3d 100644 --- a/arch/x86/include/asm/apic.h +++ b/arch/x86/include/asm/apic.h @@ -644,8 +644,8 @@ 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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