On Mon, 2012-09-10 at 12:58 +0800, Li Zhong wrote:
> There are a few tracepoints in the interrupt code path, which is before
> irq_enter(), or after irq_exit(), like
> trace_irq_entry()/trace_irq_exit() in do_IRQ(),
> trace_timer_interrupt_entry()/trace_timer_interrupt_exit() in
> timer_interrupt().
>
> If the interrupt is from idle(), and because tracepoint contains RCU
> read-side critical section, we could see following suspicious RCU usage
> reported:
.../...
> This is because the RCU usage in interrupt context should be used in
> area marked by rcu_irq_enter()/rcu_irq_exit(), called in
> irq_enter()/irq_exit() respectively.
>
> Could we add a new tracepoint trace_***_rcuirq, like trace_***_rcuidle
> to avoid the report? like the code attached below.
>
> Or could we just move these tracepoints inside the
> irq_enter()/irq_exit() area? (Seems not good for the timer_interrupt
> case).
I'd say just move them in. Anton, any objection ?
> Thanks, Zhong
>
> Signed-off-by: Li Zhong <zh...@linux.vnet.ibm.com>
> ---
> arch/powerpc/kernel/irq.c | 4 ++--
> arch/powerpc/kernel/time.c | 4 ++--
> include/linux/tracepoint.h | 10 ++++++++++
> 3 files changed, 14 insertions(+), 4 deletions(-)
>
> diff --git a/arch/powerpc/kernel/irq.c b/arch/powerpc/kernel/irq.c
> index 1f017bb..f0ac4e7 100644
> --- a/arch/powerpc/kernel/irq.c
> +++ b/arch/powerpc/kernel/irq.c
> @@ -489,7 +489,7 @@ void do_IRQ(struct pt_regs *regs)
> struct pt_regs *old_regs = set_irq_regs(regs);
> unsigned int irq;
>
> - trace_irq_entry(regs);
> + trace_irq_entry_rcuirq(regs);
>
> irq_enter();
>
> @@ -514,7 +514,7 @@ void do_IRQ(struct pt_regs *regs)
> irq_exit();
> set_irq_regs(old_regs);
>
> - trace_irq_exit(regs);
> + trace_irq_exit_rcuirq(regs);
> }
>
> void __init init_IRQ(void)
> diff --git a/arch/powerpc/kernel/time.c b/arch/powerpc/kernel/time.c
> index e49e931..cbd6607 100644
> --- a/arch/powerpc/kernel/time.c
> +++ b/arch/powerpc/kernel/time.c
> @@ -493,7 +493,7 @@ void timer_interrupt(struct pt_regs * regs)
> */
> may_hard_irq_enable();
>
> - trace_timer_interrupt_entry(regs);
> + trace_timer_interrupt_entry_rcuirq(regs);
>
> __get_cpu_var(irq_stat).timer_irqs++;
>
> @@ -532,7 +532,7 @@ void timer_interrupt(struct pt_regs * regs)
> irq_exit();
> set_irq_regs(old_regs);
>
> - trace_timer_interrupt_exit(regs);
> + trace_timer_interrupt_exit_rcuirq(regs);
> }
>
> /*
> diff --git a/include/linux/tracepoint.h b/include/linux/tracepoint.h
> index 802de56..f7672d5 100644
> --- a/include/linux/tracepoint.h
> +++ b/include/linux/tracepoint.h
> @@ -161,6 +161,16 @@ static inline void
> tracepoint_synchronize_unregister(void)
> rcu_idle_exit(), \
> rcu_idle_enter()); \
> } \
> + static inline void trace_##name##_rcuirq(proto) \
> + { \
> + if (static_key_false(&__tracepoint_##name.key)) \
> + __DO_TRACE(&__tracepoint_##name, \
> + TP_PROTO(data_proto), \
> + TP_ARGS(data_args), \
> + TP_CONDITION(cond), \
> + rcu_irq_enter(), \
> + rcu_irq_exit()); \
> + } \
> static inline int \
> register_trace_##name(void (*probe)(data_proto), void *data) \
> { \
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