Messages in this thread |  | | Date | Sun, 16 Oct 2016 15:39:11 +0200 | From | Peter Zijlstra <> | Subject | Re: [PATCH] x86/smp: Add irq_enter/exit() in smp_reschedule_interrupt() |
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On Fri, Oct 14, 2016 at 09:48:53AM +0800, Wanpeng Li wrote: > =============================== > [ 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@kernel.org> > Cc: Mike Galbraith <efault@gmx.de> > Cc: Peter Zijlstra <peterz@infradead.org> > Cc: Thomas Gleixner <tglx@linutronix.de> > Signed-off-by: Wanpeng Li <wanpeng.li@hotmail.com> > --- > 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(); > ack_APIC_irq(); > __smp_reschedule_interrupt(); > + irq_exit();
Urgh, I really hate this...
So now we're making a very frequent interrupt slower because of debug code :/
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