From: Wanpeng Li <wanpeng.li@xxxxxxxxxxx> This patch has been added to the 3.12 stable tree. If you have any objections, please let us know. =============== commit b0f48706a176b71a6e54f399d7404bbeeaa7cfab upstream. =============================== [ INFO: suspicious RCU usage. ] 4.8.0-rc6+ #5 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/2/0. stack backtrace: CPU: 2 PID: 0 Comm: swapper/2 Not tainted 4.8.0-rc6+ #5 Hardware name: Dell Inc. OptiPlex 7020/0F5C5X, BIOS A03 01/08/2015 0000000000000000 ffff8d1bd6003f10 ffffffff94446949 ffff8d1bd4a68000 0000000000000001 ffff8d1bd6003f40 ffffffff940e9247 ffff8d1bbdfcf3d0 000000000000080b 0000000000000000 0000000000000000 ffff8d1bd6003f70 Call Trace: <IRQ> [<ffffffff94446949>] dump_stack+0x99/0xd0 [<ffffffff940e9247>] lockdep_rcu_suspicious+0xe7/0x120 [<ffffffff9448e0d5>] do_trace_write_msr+0x135/0x140 [<ffffffff9406e750>] native_write_msr+0x20/0x30 [<ffffffff9406503d>] native_apic_msr_eoi_write+0x1d/0x30 [<ffffffff9405b17e>] smp_trace_call_function_interrupt+0x1e/0x270 [<ffffffff948cb1d6>] trace_call_function_interrupt+0x96/0xa0 <EOI> [<ffffffff947200f4>] ? cpuidle_enter_state+0xe4/0x360 [<ffffffff947200df>] ? cpuidle_enter_state+0xcf/0x360 [<ffffffff947203a7>] cpuidle_enter+0x17/0x20 [<ffffffff940df008>] cpu_startup_entry+0x338/0x4d0 [<ffffffff9405bfc4>] start_secondary+0x154/0x180 This can be reproduced readily by running ftrace test case of kselftest. Move the irq_enter() call before ack_APIC_irq(), because irq_enter() tells the RCU susbstems to end the extended quiescent state, so that the following trace call in ack_APIC_irq() works correctly. The same applies to exiting_ack_irq() which calls ack_APIC_irq() after irq_exit(). [ tglx: Massaged changelog ] Signed-off-by: Wanpeng Li <wanpeng.li@xxxxxxxxxxx> Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx> Cc: Wanpeng Li <wanpeng.li@xxxxxxxxxxx> Link: http://lkml.kernel.org/r/1474198491-3738-1-git-send-email-wanpeng.li@xxxxxxxxxxx Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx> Acked-by: Joerg Roedel <jroedel@xxxxxxx> Signed-off-by: Jiri Slaby <jslaby@xxxxxxx> --- arch/x86/include/asm/apic.h | 3 +-- arch/x86/kernel/smp.c | 2 +- 2 files changed, 2 insertions(+), 3 deletions(-) diff --git a/arch/x86/include/asm/apic.h b/arch/x86/include/asm/apic.h index 29559831c94f..43849c3d6275 100644 --- a/arch/x86/include/asm/apic.h +++ b/arch/x86/include/asm/apic.h @@ -710,9 +710,8 @@ static inline void exiting_irq(void) static inline void exiting_ack_irq(void) { - irq_exit(); - /* Ack only at the end to avoid potential reentry */ ack_APIC_irq(); + irq_exit(); } extern void ioapic_zap_locks(void); diff --git a/arch/x86/kernel/smp.c b/arch/x86/kernel/smp.c index 7c3a5a61f2e4..e5d895fa1fe0 100644 --- a/arch/x86/kernel/smp.c +++ b/arch/x86/kernel/smp.c @@ -267,8 +267,8 @@ __visible void smp_reschedule_interrupt(struct pt_regs *regs) static inline void smp_entering_irq(void) { - ack_APIC_irq(); irq_enter(); + ack_APIC_irq(); } __visible void smp_trace_reschedule_interrupt(struct pt_regs *regs) -- 2.11.0 -- To unsubscribe from this list: send the line "unsubscribe stable" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html