On Fri, 25 Aug 2017, Steven Rostedt wrote:
> On Fri, 25 Aug 2017 12:31:17 +0200
> Thomas Gleixner <t...@linutronix.de> wrote:
>
>
> > -__visible void __irq_entry smp_trace_reschedule_interrupt(struct pt_regs
> > *regs)
> > -{
> > - /*
> > - * Need to call irq_enter() before calling the trace point.
> > - * __smp_reschedule_interrupt() calls irq_enter/exit() too (in
> > - * scheduler_ipi(). This is OK, since those functions are allowed
> > - * to nest.
> > - */
> > - ipi_entering_ack_irq();
> > - trace_reschedule_entry(RESCHEDULE_VECTOR);
> > + if (trace_irqvectors_enabled()) {
> > + /*
> > + * scheduler_ipi() might call irq_enter() as well, but
> > + * nested calls are fine.
> > + */
> > + irq_enter();
> > + trace_reschedule_entry(RESCHEDULE_VECTOR);
> > + }
> > +
> > inc_irq_stat(irq_resched_count);
> > scheduler_ipi();
> > - trace_reschedule_exit(RESCHEDULE_VECTOR);
> > - exiting_irq();
> > +
> > + if (trace_irqvectors_enabled()) {
> > + trace_reschedule_exit(RESCHEDULE_VECTOR);
> > + irq_exit();
>
> This is racy. If the static key gets changed on one and not the other,
> we lose the irq_enter/irq_exit match.
Indeed. Good point. Fixed up version below.
Thanks,
tglx
8<---------------------
--- a/arch/x86/include/asm/hw_irq.h
+++ b/arch/x86/include/asm/hw_irq.h
@@ -48,7 +48,7 @@ extern asmlinkage void call_function_sin
#ifdef CONFIG_TRACING
/* Interrupt handlers registered during init_IRQ */
-extern void trace_reschedule_interrupt(void);
+#define trace_reschedule_interrupt reschedule_interrupt
#define trace_call_function_interrupt call_function_interrupt
#define trace_call_function_single_interrupt call_function_single_interrupt
#define trace_thermal_interrupt thermal_interrupt
--- a/arch/x86/kernel/smp.c
+++ b/arch/x86/kernel/smp.c
@@ -254,37 +254,27 @@ static void native_stop_other_cpus(int w
}
/*
- * Reschedule call back.
+ * Reschedule call back. KVM uses this interrupt to force a cpu out of
+ * guest mode
*/
-static inline void __smp_reschedule_interrupt(void)
-{
- inc_irq_stat(irq_resched_count);
- scheduler_ipi();
-}
-
__visible void __irq_entry smp_reschedule_interrupt(struct pt_regs *regs)
{
ack_APIC_irq();
- __smp_reschedule_interrupt();
- /*
- * KVM uses this interrupt to force a cpu out of guest mode
- */
-}
-
-__visible void __irq_entry smp_trace_reschedule_interrupt(struct pt_regs *regs)
-{
- /*
- * Need to call irq_enter() before calling the trace point.
- * __smp_reschedule_interrupt() calls irq_enter/exit() too (in
- * scheduler_ipi(). This is OK, since those functions are allowed
- * to nest.
- */
- ipi_entering_ack_irq();
- trace_reschedule_entry(RESCHEDULE_VECTOR);
inc_irq_stat(irq_resched_count);
+
+ if (trace_irqvectors_enabled()) {
+ /*
+ * scheduler_ipi() might call irq_enter() as well, but
+ * nested calls are fine.
+ */
+ irq_enter();
+ trace_reschedule_entry(RESCHEDULE_VECTOR);
+ scheduler_ipi();
+ trace_reschedule_exit(RESCHEDULE_VECTOR);
+ irq_exit();
+ return;
+ }
scheduler_ipi();
- trace_reschedule_exit(RESCHEDULE_VECTOR);
- exiting_irq();
}
__visible void __irq_entry smp_call_function_interrupt(struct pt_regs *regs)
