2016-10-16 21:39 GMT+08:00 Peter Zijlstra <[email protected]>: > 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 <[email protected]> >> Cc: Mike Galbraith <[email protected]> >> Cc: Peter Zijlstra <[email protected]> >> Cc: Thomas Gleixner <[email protected]> >> Signed-off-by: Wanpeng Li <[email protected]> >> --- >> 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 :/
Do you have a better idea? :) Regards, Wanpeng Li
