From: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
To: rostedt <rostedt@goodmis.org>
Cc: linux-kernel <linux-kernel@vger.kernel.org>,
Ingo Molnar <mingo@kernel.org>,
Andrew Morton <akpm@linux-foundation.org>,
"Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Subject: Re: [PATCH 7/5] tracing: Make sure rcu_irq_enter() can work for trace_*_rcuidle() trace events
Date: Fri, 7 Apr 2017 17:49:17 +0000 (UTC) [thread overview]
Message-ID: <1679331943.4538.1491587357083.JavaMail.zimbra@efficios.com> (raw)
In-Reply-To: <20170407132613.4a9fa430@gandalf.local.home>
----- On Apr 7, 2017, at 1:26 PM, rostedt rostedt@goodmis.org wrote:
> On Fri, 7 Apr 2017 17:19:05 +0000 (UTC)
> Mathieu Desnoyers <mathieu.desnoyers@efficios.com> wrote:
>
[...]
>> > ---
>> > include/linux/tracepoint.h | 2 ++
>> > 1 file changed, 2 insertions(+)
>> >
>> > diff --git a/include/linux/tracepoint.h b/include/linux/tracepoint.h
>> > index f72fcfe..8baef96 100644
>> > --- a/include/linux/tracepoint.h
>> > +++ b/include/linux/tracepoint.h
>> > @@ -159,6 +159,8 @@ extern void syscall_unregfunc(void);
>> > TP_PROTO(data_proto), \
>> > TP_ARGS(data_args), \
>> > TP_CONDITION(cond), \
>> > + if (WARN_ON_ONCE(rcu_irq_enter_disabled())) \
>> > + return; \
>>
>> I must admit that it's a bit odd to have:
>>
>> if (WARN_ON_ONCE(rcu_irq_enter_disabled()))
>> return;
>> rcu_irq_enter_irqson()
>
> Welcome to MACRO MAGIC!
>
>>
>> as one argument to the __DO_TRACE() macro. To me it's a bit unexpected
>> coding-style wise. Am I the only one not comfortable with the proposed
>> syntax ?
>
> The entire TRACE_EVENT()/__DO_TRACE() is special.
>
> I thought about add yet another parameter, but as it doesn't change
> much, I figured this was good enough. We could beak it up if you like:
>
> #define RCU_IRQ_ENTER_CHECK \
> if (WARN_ON_ONCE(rcu_irq_enter_disabled()) \
> return; \
> rcu_irq_enter_irqson();
>
> [..]
> __DO_TRACE(&__tracepoint_##name, \
> TP_PROTO(data_proto), \
> TP_ARGS(data_args), \
> TP_CONDITION(cond), \
> PARAMS(RCU_IRQ_ENTER_CHECK), \
> rcu_irq_exit_irqson()); \
>
>
> Would that make you feel more comfortable?
No, it's almost worse and adds still adds a return that apply within __DO_TRACE(),
but which is passed as an argument (code as macro argument), which I find really
unsettling.
I would prefer to add a new argument to __DO_TRACE, which we can call
"checkrcu", e.g.:
#define __DO_TRACE(tp, proto, args, cond, checkrcu, prercu, postrcu) \
do { \
struct tracepoint_func *it_func_ptr; \
void *it_func; \
void *__data; \
\
if (!((cond) && (checkrcu))) \
return; \
prercu; \
rcu_read_lock_sched_notrace(); \
it_func_ptr = rcu_dereference_sched((tp)->funcs); \
if (it_func_ptr) { \
do { \
it_func = (it_func_ptr)->func; \
__data = (it_func_ptr)->data; \
((void(*)(proto))(it_func))(args); \
} while ((++it_func_ptr)->func); \
} \
rcu_read_unlock_sched_notrace(); \
postrcu; \
} while (0)
And use it like this:
#define __DECLARE_TRACE_RCU(name, proto, args, cond, data_proto, data_args) \
static inline void trace_##name##_rcuidle(proto) \
{ \
if (static_key_false(&__tracepoint_##name.key)) \
__DO_TRACE(&__tracepoint_##name, \
TP_PROTO(data_proto), \
TP_ARGS(data_args), \
TP_CONDITION(cond), \
!WARN_ON_ONCE(rcu_irq_enter_disabled()),\
rcu_irq_enter_irqson(), \
rcu_irq_exit_irqson()); \
}
This way we only pass evaluated expression (not code with "return" that
changes the flow) as arguments to __DO_TRACE, which makes it behave more
like a "sub-function", which is what we usually expect.
Thanks,
Mathieu
--
Mathieu Desnoyers
EfficiOS Inc.
http://www.efficios.com
next prev parent reply other threads:[~2017-04-07 17:48 UTC|newest]
Thread overview: 39+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-04-07 14:01 [PATCH 0/5 v2] tracing: Add usecase of synchronize_rcu_tasks() and stack_tracer_disable() Steven Rostedt
2017-04-07 14:01 ` [PATCH 1/5 v2] ftrace: Add use of synchronize_rcu_tasks() with dynamic trampolines Steven Rostedt
2017-04-07 14:01 ` [PATCH 2/5 v2] tracing: Replace the per_cpu() with this_cpu() in trace_stack.c Steven Rostedt
2017-04-07 14:36 ` Paul E. McKenney
2017-04-07 14:48 ` Steven Rostedt
2017-04-07 15:08 ` Paul E. McKenney
2017-04-07 14:01 ` [PATCH 3/5 v2] tracing: Add stack_tracer_disable/enable() functions Steven Rostedt
2017-04-07 14:22 ` Steven Rostedt
2017-04-07 14:25 ` [PATCH 3/5 v2.1] " Steven Rostedt
2017-04-07 14:01 ` [PATCH 4/5 v2] tracing: Rename trace_active to disable_stack_tracer and inline its modification Steven Rostedt
2017-04-07 14:01 ` [PATCH 5/5 v2] rcu: Fix dyntick-idle tracing Steven Rostedt
2017-04-07 14:40 ` Paul E. McKenney
2017-04-07 14:53 ` Steven Rostedt
2017-04-07 15:09 ` Paul E. McKenney
2017-04-07 15:29 ` Steven Rostedt
2017-04-07 14:43 ` [PATCH 0/5 v2] tracing: Add usecase of synchronize_rcu_tasks() and stack_tracer_disable() Paul E. McKenney
2017-04-07 14:58 ` Steven Rostedt
2017-04-07 15:11 ` Paul E. McKenney
2017-04-07 15:28 ` Steven Rostedt
2017-04-07 16:35 ` [PATCH 6/5]rcu/tracing: Add rcu_disabled to denote when rcu_irq_enter() will not work Steven Rostedt
2017-04-07 16:42 ` Paul E. McKenney
2017-04-07 16:44 ` Steven Rostedt
2017-04-07 16:53 ` Paul E. McKenney
2017-04-07 17:03 ` [PATCH 6/5 v2] rcu/tracing: " Steven Rostedt
2017-04-07 17:15 ` Paul E. McKenney
2017-04-07 17:06 ` [PATCH 7/5] tracing: Make sure rcu_irq_enter() can work for trace_*_rcuidle() trace events Steven Rostedt
2017-04-07 17:15 ` Paul E. McKenney
2017-04-07 17:19 ` Mathieu Desnoyers
2017-04-07 17:26 ` Steven Rostedt
2017-04-07 17:32 ` Steven Rostedt
2017-04-07 17:49 ` Mathieu Desnoyers [this message]
2017-04-07 17:55 ` Steven Rostedt
2017-04-07 18:10 ` [PATCH 7/5 v3] " Steven Rostedt
2017-04-07 18:17 ` Mathieu Desnoyers
2017-04-07 19:41 ` [PATCH 7/5 v4] " Steven Rostedt
2017-04-07 19:43 ` Steven Rostedt
2017-04-10 17:11 ` Mathieu Desnoyers
2017-04-07 17:28 ` [PATCH 7/5] " Steven Rostedt
2017-04-07 17:48 ` [PATCH 7/5 v2] " Steven Rostedt
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