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| author | Wanpeng Li <wanpeng.li@hotmail.com> | 2016-11-07 04:13:40 +0100 |
|---|---|---|
| committer | Thomas Gleixner <tglx@linutronix.de> | 2016-11-09 22:03:14 +0100 |
| commit | 8ca225520e278e41396dab0524989f4848626f83 (patch) | |
| tree | c71f406bb7dc56ef41e7043672b5842593998f09 /arch/x86/kernel/smp.c | |
| parent | x86/msr: Add wrmsr_notrace() (diff) | |
| download | linux-8ca225520e278e41396dab0524989f4848626f83.tar.xz linux-8ca225520e278e41396dab0524989f4848626f83.zip | |
x86/apic: Prevent tracing on apic_msr_write_eoi()
The following RCU lockdep warning led to adding irq_enter()/irq_exit() into
smp_reschedule_interrupt():
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.
do_trace_write_msr
native_write_msr
native_apic_msr_eoi_write
smp_reschedule_interrupt
reschedule_interrupt
As Peterz pointed out:
| So now we're making a very frequent interrupt slower because of debug
| code.
|
| The thing is, many many smp_reschedule_interrupt() invocations don't
| actually execute anything much at all and are only sent to tickle the
| return to user path (which does the actual preemption).
|
| Having to do the whole irq_enter/irq_exit dance just for this unlikely
| debug case totally blows.
Use the wrmsr_notrace() variant in native_apic_msr_write_eoi, annotate the
kvm variant with notrace and add a native_apic_eoi callback to the apic
structure so KVM guests are covered as well.
This allows to revert the irq_enter/irq_exit dance in
smp_reschedule_interrupt().
Suggested-by: Peter Zijlstra <peterz@infradead.org>
Suggested-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Wanpeng Li <wanpeng.li@hotmail.com>
Acked-by: Paolo Bonzini <pbonzini@redhat.com>
Cc: kvm@vger.kernel.org
Cc: Mike Galbraith <efault@gmx.de>
Cc: Borislav Petkov <bp@alien8.de>
Link: http://lkml.kernel.org/r/1478488420-5982-3-git-send-email-wanpeng.li@hotmail.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Diffstat (limited to 'arch/x86/kernel/smp.c')
| -rw-r--r-- | arch/x86/kernel/smp.c | 2 |
1 files changed, 0 insertions, 2 deletions
diff --git a/arch/x86/kernel/smp.c b/arch/x86/kernel/smp.c index c00cb64bc0a1..68f8cc222f25 100644 --- a/arch/x86/kernel/smp.c +++ b/arch/x86/kernel/smp.c @@ -261,10 +261,8 @@ 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(); /* * KVM uses this interrupt to force a cpu out of guest mode */ |